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2007, 26 (S2): -3600 doi:
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2007, 26 (S2): -3600 doi:
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ANALYSIS OF GROUND SUBSIDENCE INDUCED BY SHALLOW-BURIED TUNNEL CONSTRUCTION AND ITS CONTROL TECHNIQUES

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2007, 26 (S2): -3601 doi:
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It is the key issue to prevent ground subsidence，especially seabed subsidence during the construction of shallow-buried subsea tunnels. So it is necessary to analyze the ground subsidence caused by the construction of shallow-buried tunnels including subsea tunnels in order to find out its forming mechanisms，inducing factors and control measures. Based on two ground subsidence accidents caused by the construction of a certain shallow-buried tunnel in Shenzhen subway，the equilibrium arch theory of М·М·Протодьяконов is used，and the forming mechanisms of ground subsidence induced by shallow-buried tunneling are presented. Predominant factors，which cause the collapse of ground，are analyzed according to stratum geological conditions and construction methods. Moreover，control techniques of avoiding ground subsidence accident are also proposed，and are applied to the tunnel construction in Shenzhen subway subsequently. Good effects were achieved in guiding the construction of the subway tunnel and ground subsidence accidents were also avoided. Research indicates that if shallow-buried tunneling can be strictly kept to the principles and technical rules of shallow-buried tunneling method，ground subsidence can be avoided effectively. The research results can provide references to preventing ground subsidence induced by construction of shallow-buried urban subway tunnels，subsea tunnels and other similar tunnel engineering.

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ANALYSIS OF GROUND SUBSIDENCE INDUCED BY SHALLOW-BURIED TUNNEL CONSTRUCTION AND ITS CONTROL TECHNIQUES

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2007, 26 (S2): -3601 doi:
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[PDF 530 KB] (857)

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It is the key issue to prevent ground subsidence，especially seabed subsidence during the construction of shallow-buried subsea tunnels. So it is necessary to analyze the ground subsidence caused by the construction of shallow-buried tunnels including subsea tunnels in order to find out its forming mechanisms，inducing factors and control measures. Based on two ground subsidence accidents caused by the construction of a certain shallow-buried tunnel in Shenzhen subway，the equilibrium arch theory of М·М·Протодьяконов is used，and the forming mechanisms of ground subsidence induced by shallow-buried tunneling are presented. Predominant factors，which cause the collapse of ground，are analyzed according to stratum geological conditions and construction methods. Moreover，control techniques of avoiding ground subsidence accident are also proposed，and are applied to the tunnel construction in Shenzhen subway subsequently. Good effects were achieved in guiding the construction of the subway tunnel and ground subsidence accidents were also avoided. Research indicates that if shallow-buried tunneling can be strictly kept to the principles and technical rules of shallow-buried tunneling method，ground subsidence can be avoided effectively. The research results can provide references to preventing ground subsidence induced by construction of shallow-buried urban subway tunnels，subsea tunnels and other similar tunnel engineering.

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STUDY ON SEISMIC RESPONSE OF LARGE SHIELD TUNNEL IN SUBMARINE LIQUEFIABLE STRATA

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2007, 26 (S2): -3609 doi:
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Employing Byrne model to simulate cyclic liquefaction of soils，a three-dimension model that consists of main tunnels，transverse evacuating passage and strata of Nanjing Yangtze River tunnel is established to study structure dynamic mechanical(stress and displacement) responses by inputting transverse and longitudinal seismic waves；and the different influences of transverse and longitudinal seismic waves on pore water pressure，effective stress are studied. The conclusion shows that the damage of transverse earthquake excitation to structure is much more serious than that of longitudinal earthquake excitation，and that the peak value of maximum tension stress of intersecting section of main tunnel-evacuating passage is about 3 MPa under transverse earthquake excitation，which is over the ultimate tensile strength of structure and will lead to a failure tendency of tension fracture. An aseismic mitigation method was proposed，and the achieved conclusion is helpful for the aseismic design of similar projects.

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STUDY ON SEISMIC RESPONSE OF LARGE SHIELD TUNNEL IN SUBMARINE LIQUEFIABLE STRATA

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2007, 26 (S2): -3609 doi:
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Employing Byrne model to simulate cyclic liquefaction of soils，a three-dimension model that consists of main tunnels，transverse evacuating passage and strata of Nanjing Yangtze River tunnel is established to study structure dynamic mechanical(stress and displacement) responses by inputting transverse and longitudinal seismic waves；and the different influences of transverse and longitudinal seismic waves on pore water pressure，effective stress are studied. The conclusion shows that the damage of transverse earthquake excitation to structure is much more serious than that of longitudinal earthquake excitation，and that the peak value of maximum tension stress of intersecting section of main tunnel-evacuating passage is about 3 MPa under transverse earthquake excitation，which is over the ultimate tensile strength of structure and will lead to a failure tendency of tension fracture. An aseismic mitigation method was proposed，and the achieved conclusion is helpful for the aseismic design of similar projects.

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RISK ASSESSMENT ON DRILL AND BLASTING METHOD OF DALIAN BAY SUBSEA TUNNEL

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2007, 26 (S2): -3616 doi:
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The subsea tunnel has complex geology conditions and surrounding environments，so there are many factors that affect the advancing rate，cost，city environment and safety during the subsea tunnel construction and operation. However，risk management theory has rarely been reported on the construction of large-scale subsea tunnel excavated by drill and blasting method. With the background of Dalian Bay subsea tunnel excavated by drill and blasting method，it will focus on the two schemes during the stage of the feasibility of the project，identifying and analyzing the construction risks，evaluating the risks by using the survey from specialists method based on confidence index. The risk assessment is mainly carried on by the four aspects，i.e. the south shore land field tunnel construction，the subsea area tunnel construction，the north shore tunnel construction and the influence of the construction upon the surrounding environments. Based on the results of risk assessment，the risk of recommended scheme is large. Finally，according to the characteristics of the risks，some measures to reduce or control the risk loss are taken，and some conclusions and suggestions are also proposed. It gives some references to the selection of scheme line and construction management in the engineering decision. Simultaneity，the risk management theory to the construction of subsea tunnel should be adopted，which can provide references to the risk assessment of other similar engineering cases.

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RISK ASSESSMENT ON DRILL AND BLASTING METHOD OF DALIAN BAY SUBSEA TUNNEL

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2007, 26 (S2): -3616 doi:
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[PDF 279 KB] (1172)

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The subsea tunnel has complex geology conditions and surrounding environments，so there are many factors that affect the advancing rate，cost，city environment and safety during the subsea tunnel construction and operation. However，risk management theory has rarely been reported on the construction of large-scale subsea tunnel excavated by drill and blasting method. With the background of Dalian Bay subsea tunnel excavated by drill and blasting method，it will focus on the two schemes during the stage of the feasibility of the project，identifying and analyzing the construction risks，evaluating the risks by using the survey from specialists method based on confidence index. The risk assessment is mainly carried on by the four aspects，i.e. the south shore land field tunnel construction，the subsea area tunnel construction，the north shore tunnel construction and the influence of the construction upon the surrounding environments. Based on the results of risk assessment，the risk of recommended scheme is large. Finally，according to the characteristics of the risks，some measures to reduce or control the risk loss are taken，and some conclusions and suggestions are also proposed. It gives some references to the selection of scheme line and construction management in the engineering decision. Simultaneity，the risk management theory to the construction of subsea tunnel should be adopted，which can provide references to the risk assessment of other similar engineering cases.

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APPLICABILITY STUDY ON ASEISMIC DESIGN METHOD OF SUBMARINE SHIELD TUNNEL

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2007, 26 (S2): -3623 doi:
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Based on structural features in both transverse and longitudinal directions，a reasonable aseismic design method for structurally complicated subriver shield tunnels with large cross-section and deep underwater pressure is proposed. For the design of transverse direction of tunnel with relatively regular ground that is different from the hypothesis of boundary displacement sine wave distribution mode，practical seismic responses from the ground where the tunnel will be constructed have been calculated according to the theory of ground stratification reflection theory. Using seismic deformation method，the seismic response of a typical section of the tunnel was analyzed. The result was used in combination with static calculations as support for aseismic designs. For the longitudinal direction，the 3D time-domain response method should be used due to the requirement of considering linear structural features，the irregular ground along longitudinal direction of the tunnel，seismic traveling wave effects，and boundary effects，etc.. The features，applications，and analytical process of these two methods are discussed. The design method has been applied to a shield tunnel crossing the Yangtze River，and the seismic behaviors and the aseismic-weaker parts of this typical subriver shield tunnel are also indicated.

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APPLICABILITY STUDY ON ASEISMIC DESIGN METHOD OF SUBMARINE SHIELD TUNNEL

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2007, 26 (S2): -3625 doi:
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[PDF 389 KB] (994)

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Based on structural features in both transverse and longitudinal directions，a reasonable aseismic design method for structurally complicated subriver shield tunnels with large cross-section and deep underwater pressure is proposed. For the design of transverse direction of tunnel with relatively regular ground that is different from the hypothesis of boundary displacement sine wave distribution mode，practical seismic responses from the ground where the tunnel will be constructed have been calculated according to the theory of ground stratification reflection theory. Using seismic deformation method，the seismic response of a typical section of the tunnel was analyzed. The result was used in combination with static calculations as support for aseismic designs. For the longitudinal direction，the 3D time-domain response method should be used due to the requirement of considering linear structural features，the irregular ground along longitudinal direction of the tunnel，seismic traveling wave effects，and boundary effects，etc.. The features，applications，and analytical process of these two methods are discussed. The design method has been applied to a shield tunnel crossing the Yangtze River，and the seismic behaviors and the aseismic-weaker parts of this typical subriver shield tunnel are also indicated.

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GROUND SETTLEMENT PREDICTION DURING CONSTRUCTION OF WUHAN YANGTZE RIVER TUNNEL

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2007, 26 (S2): -3631 doi:
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Wuhan Yangtze River Tunnel(WYRT)，which is the first tunnel crossing through the Yangtze River，will be the main road for connecting two towns，namely，Wuchang and Hankou in urban area of Wuhan City，China. Because the geological condition in Wuhan City is much complicated，shielding tunnel method is employed for the river-crossing part，and cut and cover method is applied to the approach tunneling. It is very important to reduce the influences of construction on surrounding environment，including buildings and pipelines. Numerical simulation method is used to predict the influences of construction on the ground settlement herein. The prediction results of ground settlement resulted from the ground loss of tunneling is presented. The results indicate that the influences resulted from tunneling on the ground surface are comparatively small when the distance to tunnel axial is more than 50 meters. With the ground loss rate increasing，the range of plastic zone of soil surrounding tunnels increases；the slope of ground settlement curve increasing results from the plastic yielding zone increasing between two bores；critical ground loss rate increases with the overburden depth in tunnel area. Making the ground loss rate to be less than 2% is very effective to minimize the ground settlement，so as to minimize the effect on surrounding buildings and pipelines. The influence of tunneling on the ground settlement decreases with the overburden depth increasing in tunnel area. Protective measures should be taken for the buildings and pipelines in range of 50 meters around the tunnel.

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GROUND SETTLEMENT PREDICTION DURING CONSTRUCTION OF WUHAN YANGTZE RIVER TUNNEL

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2007, 26 (S2): -3631 doi:
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Wuhan Yangtze River Tunnel(WYRT)，which is the first tunnel crossing through the Yangtze River，will be the main road for connecting two towns，namely，Wuchang and Hankou in urban area of Wuhan City，China. Because the geological condition in Wuhan City is much complicated，shielding tunnel method is employed for the river-crossing part，and cut and cover method is applied to the approach tunneling. It is very important to reduce the influences of construction on surrounding environment，including buildings and pipelines. Numerical simulation method is used to predict the influences of construction on the ground settlement herein. The prediction results of ground settlement resulted from the ground loss of tunneling is presented. The results indicate that the influences resulted from tunneling on the ground surface are comparatively small when the distance to tunnel axial is more than 50 meters. With the ground loss rate increasing，the range of plastic zone of soil surrounding tunnels increases；the slope of ground settlement curve increasing results from the plastic yielding zone increasing between two bores；critical ground loss rate increases with the overburden depth in tunnel area. Making the ground loss rate to be less than 2% is very effective to minimize the ground settlement，so as to minimize the effect on surrounding buildings and pipelines. The influence of tunneling on the ground settlement decreases with the overburden depth increasing in tunnel area. Protective measures should be taken for the buildings and pipelines in range of 50 meters around the tunnel.

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COMPARISON OF DIFFERENT WORKING PROCEDURES BY CRD METHOD FOR SHALLOW-BURIED SUBSEA TUNNEL EXCAVATION

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2007, 26 (S2): -3639 doi:
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Xiamen East Passageway Xiang¢an subsea tunnel under construction is the first subsea tunnel in China. CRD method is adopted for the unfavourable geological conditions on shallow-buried excavation area through strong weathered granite，which holds higher water content and lower intensity. Due to the unfavourable geological conditions and no experiences referred to foreign similar projects，the method of combining in-situ monitoring with numerical simulation is employed to analyze the influence of different working procedures of settlements with convergence and internal forces of arch crown. The achieved results agree well with the analytical result. The research indicates that the proportion of settlement of arch crown by different steps is basically the same by the comparison between CRD1，2 excavation ahead and CRD1，3 on the geological conditions specifically，but settlement of arch crown on CRD1，3 by the first working procedure is approximately 70%，45% higher than the second one while convergence on CRD1 is about 15%. In addition，internal forces are a little higher than those of the second working procedure. The result can provide references to the information-oriented construction of tunnel as well as experience for similar projects.

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COMPARISON OF DIFFERENT WORKING PROCEDURES BY CRD METHOD FOR SHALLOW-BURIED SUBSEA TUNNEL EXCAVATION

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2007, 26 (S2): -3639 doi:
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[PDF 275 KB] (740)

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Xiamen East Passageway Xiang¢an subsea tunnel under construction is the first subsea tunnel in China. CRD method is adopted for the unfavourable geological conditions on shallow-buried excavation area through strong weathered granite，which holds higher water content and lower intensity. Due to the unfavourable geological conditions and no experiences referred to foreign similar projects，the method of combining in-situ monitoring with numerical simulation is employed to analyze the influence of different working procedures of settlements with convergence and internal forces of arch crown. The achieved results agree well with the analytical result. The research indicates that the proportion of settlement of arch crown by different steps is basically the same by the comparison between CRD1，2 excavation ahead and CRD1，3 on the geological conditions specifically，but settlement of arch crown on CRD1，3 by the first working procedure is approximately 70%，45% higher than the second one while convergence on CRD1 is about 15%. In addition，internal forces are a little higher than those of the second working procedure. The result can provide references to the information-oriented construction of tunnel as well as experience for similar projects.

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DEFORMATION MODEL OF BACKFILL GROUTING AND GROUND MOVEMENT ANALYSIS OF SHIELD TUNNEL

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2007, 26 (S2): -3646 doi:
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An inevitable annular space named tail void is created at the rear of shield machines. This void is of importance with respect to subground settlements. During shield tunnel construction，the grout is being pumped in the void through a number of injection holes. With the hydration of cement and liquid loss after backfill process being completed，the grout volumes shrinkage leads to ground loss and induces the ground movement. The grout deformation and mechanical property variation can directly affect soil stresses releasing，ground movement，and earth pressures acting on segment. Utilizing the self-developed small scale element model of backfill grouting，the change laws of grout deformation are studied under different grouting pressures，different grout material mixtures in sandy soil. Based on grout deformation laws，mathematical model is proposed to simulate grout deformation. Identification of the gap parameter is one of the most important steps when using an analytical method to predict ground movement. Gap parameters can be obtained more exactly through grout deformation model.

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DEFORMATION MODEL OF BACKFILL GROUTING AND GROUND MOVEMENT ANALYSIS OF SHIELD TUNNEL

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2007, 26 (S2): -3646 doi:
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[PDF 346 KB] (1014)

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An inevitable annular space named tail void is created at the rear of shield machines. This void is of importance with respect to subground settlements. During shield tunnel construction，the grout is being pumped in the void through a number of injection holes. With the hydration of cement and liquid loss after backfill process being completed，the grout volumes shrinkage leads to ground loss and induces the ground movement. The grout deformation and mechanical property variation can directly affect soil stresses releasing，ground movement，and earth pressures acting on segment. Utilizing the self-developed small scale element model of backfill grouting，the change laws of grout deformation are studied under different grouting pressures，different grout material mixtures in sandy soil. Based on grout deformation laws，mathematical model is proposed to simulate grout deformation. Identification of the gap parameter is one of the most important steps when using an analytical method to predict ground movement. Gap parameters can be obtained more exactly through grout deformation model.

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DISPLACEMENT MONITORING ANALYSIS OF XIAMEN XIANG¢AN SUBSEA TUNNEL IN LANDSIDE SECTION CONSTRUCTED
WITH CRD METHOD

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2007, 26 (S2): -3653 doi:
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The landside section of Xiamen Xiang¢an subsea tunnel was under unfavorable ground condition with small buried depth and 3-lane large-section，which mainly is constructed by center cross diagram(CRD) method. Measured displacements and construction method of CRD were also analyzed. Results indicated that the estimation of measured displacement of CRD method should be dependent primarily on arch-crown subsidence and secondly on horizontal covergence. The curve of measured arch-crown subsidence of CRD method vs. time normally was in a shape of uplifted zigzag with a final stable value，and the subsidence is caused by each heading constituted of a certain proportion of final subsidence，which could be used as an index to forecast and control the final subsidence. The primary lining of CRD1 should be closed as soon as possible for reducing the final subsidence since half of which was caused during excavation of CRD1；experiences in this case show that the total arch-crown subsidence of CRD1 should be controlled within 200 mm for the safe operation. Combining measured displacements with field construction experiences，it shows that the guarantee of structure safety in Xiang¢an subsea tunnel is 10–15 m for space between border upon headings，1.0–1.5 m for each round of excavation(only 0.5 m for extreme poor ground condition)，6 m for maximal of step length in heading，and the invert arch should be closed as soon as possible. The suggestion is verified in construction of Xiamen Xiang¢an subsea tunnel.

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DISPLACEMENT MONITORING ANALYSIS OF XIAMEN XIANG¢AN SUBSEA TUNNEL IN LANDSIDE SECTION CONSTRUCTED
WITH CRD METHOD

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2007, 26 (S2): -3653 doi:
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[PDF 228 KB] (712)

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The landside section of Xiamen Xiang¢an subsea tunnel was under unfavorable ground condition with small buried depth and 3-lane large-section，which mainly is constructed by center cross diagram(CRD) method. Measured displacements and construction method of CRD were also analyzed. Results indicated that the estimation of measured displacement of CRD method should be dependent primarily on arch-crown subsidence and secondly on horizontal covergence. The curve of measured arch-crown subsidence of CRD method vs. time normally was in a shape of uplifted zigzag with a final stable value，and the subsidence is caused by each heading constituted of a certain proportion of final subsidence，which could be used as an index to forecast and control the final subsidence. The primary lining of CRD1 should be closed as soon as possible for reducing the final subsidence since half of which was caused during excavation of CRD1；experiences in this case show that the total arch-crown subsidence of CRD1 should be controlled within 200 mm for the safe operation. Combining measured displacements with field construction experiences，it shows that the guarantee of structure safety in Xiang¢an subsea tunnel is 10–15 m for space between border upon headings，1.0–1.5 m for each round of excavation(only 0.5 m for extreme poor ground condition)，6 m for maximal of step length in heading，and the invert arch should be closed as soon as possible. The suggestion is verified in construction of Xiamen Xiang¢an subsea tunnel.

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FIRE-PROOF SECTION DESIGN OF RIVER-CROSSING ROAD TUNNELS

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2007, 26 (S2): -3659 doi:
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Tunnel fire becomes a hot issue，and the problem how to consider the future fire probability during the design of the tunnel is needed to consider. The fire-proof section has to be planned according to staff escape speed，but also depending on the essential time of escape. Three important factors of tunnel fire，i.e. the temperature，concentration of carbon monoxide(CO) and visibility，which will threaten people¢s lives seriously，are analysed. It is a key of evacuation route design to make people escape from dangerous area safely in a certain time. So the time when temperature，visibility and consistency of carbon monoxide in tunnel menace people¢s lives is also studied. From this point of view，adopting computational fluent dynamics software FDS and evacuation model Tunev(tunnel evacuation)，the available safety egress time(ASET)and required safety egress time(RSET) with the example of Shanghai river-crossing road tunnel are simulated. Then，the preliminary sketch of the distance of the tunnel evacuation section and the capacity of the escaping staircase are also presented. Finally，the fire-proof section is designed，which may provide some references to the escape-rescue design of tunnels.

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FIRE-PROOF SECTION DESIGN OF RIVER-CROSSING ROAD TUNNELS

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2007, 26 (S2): -3659 doi:
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Tunnel fire becomes a hot issue，and the problem how to consider the future fire probability during the design of the tunnel is needed to consider. The fire-proof section has to be planned according to staff escape speed，but also depending on the essential time of escape. Three important factors of tunnel fire，i.e. the temperature，concentration of carbon monoxide(CO) and visibility，which will threaten people¢s lives seriously，are analysed. It is a key of evacuation route design to make people escape from dangerous area safely in a certain time. So the time when temperature，visibility and consistency of carbon monoxide in tunnel menace people¢s lives is also studied. From this point of view，adopting computational fluent dynamics software FDS and evacuation model Tunev(tunnel evacuation)，the available safety egress time(ASET)and required safety egress time(RSET) with the example of Shanghai river-crossing road tunnel are simulated. Then，the preliminary sketch of the distance of the tunnel evacuation section and the capacity of the escaping staircase are also presented. Finally，the fire-proof section is designed，which may provide some references to the escape-rescue design of tunnels.

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SELECTION OF ADVANCING MODE OF DOUBLE-SHIELDED TBM IN WEAK ROCK MASSES

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2007, 26 (S2): -3668 doi:
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To investigate the selection of the advancing mode of the double-shielded tunnel boring machines(TBM) in the weak rock masses of “Datong River-Huangshui River”Water Transfer Project，a three-dimensional finite element model is established to simulate the advancing of the double-shield TBM. The failure mechanisms of the weak rock mass under the gripper pads and the interaction between the weak rock masses and gripper pads are investigated. It shows that the gripper pads pressure will cause the shearing and tension failure of the weak rock mass. When the in-situ stress is mainly caused by the gravity and the lateral pressure with coefficient l＜1，the gripper pads pressure will probably cause the failure zone extend and large extent tensile failure zone appear. In addition，the critical strength of the weak rock masses is proposed when the pressure extends the failure zones. Under this condition，the single shield advancing mode and the double-shield advancing mode with lower parameters should be adopted. In the deeper depth with the lateral pressure coefficient l≥1，the gripper pads pressure will have limited influences on the surrounding rock masses and even can not cause the failure zone extend，but，the failure zone may be damaged further. In this case，the primary double-shield advancing mode should be adopted when the residual strength of the weak rock masses is high.

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SELECTION OF ADVANCING MODE OF DOUBLE-SHIELDED TBM IN WEAK ROCK MASSES

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2007, 26 (S2): -3668 doi:
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HYDRAULIC LINING-GROUND INTERACTION OF SUBSEA TUNNELS

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2007, 26 (S2): -3674 doi:
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[PDF 304 KB] (1185)

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Subsea tunnel will influence the hydraulic regime of the surrounding ground and tends to induce seepage towards the excavation boundary. Tunnel linings are almost never completely impermeable and it is also not practical to build an impervious tunnel. Generally，tunnels are thus designed to operate under a drained condition. A great deal of uncertainties，however，remain concerning leakage controls in subsea tunnels. Therefore，in many cases，owners，designers and contractors are interested in evaluating the benefits of considering partially or fully drained tunnel linings. The design procedures of a subsea tunnel have to address any detrimental effects associated with groundwater movement. Unfortunately，the complicated hydraulic boundary conditions and the long period required to measure the behaviors are the main difficulties in identifying the hydraulic interaction that is paramount in case of subsea tunnels. In subsea tunnels，the main hydraulic factors to be controlled are the amount of leakage and water pressures on the linings. Thus，the paper attempts to investigate the hydraulic lining-ground interaction using a coupled numerical approach. Adopting specially devised elements that can consider the permeability of drainage systems will represent the deterioration of drainage system. The long-term hydraulic lining-ground interaction including the relationship between the amount of leakage and the water pressure on the lining is studied. Design considering the control of leakage and the evaluation of water pressure for the subsea tunnels is also presented.

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HYDRAULIC LINING-GROUND INTERACTION OF SUBSEA TUNNELS

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2007, 26 (S2): -3674 doi:
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[PDF 304 KB] (962)

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Subsea tunnel will influence the hydraulic regime of the surrounding ground and tends to induce seepage towards the excavation boundary. Tunnel linings are almost never completely impermeable and it is also not practical to build an impervious tunnel. Generally，tunnels are thus designed to operate under a drained condition. A great deal of uncertainties，however，remain concerning leakage controls in subsea tunnels. Therefore，in many cases，owners，designers and contractors are interested in evaluating the benefits of considering partially or fully drained tunnel linings. The design procedures of a subsea tunnel have to address any detrimental effects associated with groundwater movement. Unfortunately，the complicated hydraulic boundary conditions and the long period required to measure the behaviors are the main difficulties in identifying the hydraulic interaction that is paramount in case of subsea tunnels. In subsea tunnels，the main hydraulic factors to be controlled are the amount of leakage and water pressures on the linings. Thus，the paper attempts to investigate the hydraulic lining-ground interaction using a coupled numerical approach. Adopting specially devised elements that can consider the permeability of drainage systems will represent the deterioration of drainage system. The long-term hydraulic lining-ground interaction including the relationship between the amount of leakage and the water pressure on the lining is studied. Design considering the control of leakage and the evaluation of water pressure for the subsea tunnels is also presented.

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J. H. Shin1，Y. S. Shin2，S. H. Kim3，H. S. Shin4

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2007, 26 (S2): -3682 doi:
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[PDF 306 KB] (1365)

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Long-term observations for tunnels have shown two interesting aspects：an increase in leakage for watertight tunnels；and a decrease for leaking tunnels. An increase in leakage may exceed the capacity of drainage system and a decrease in leakage cause unexpected water pressure on the lining. Both excess leakage and additional water pressure are detrimental to running tunnels. Therefore，during tunnel operation，the flow behaviors around tunnel should be appropriately controlled. One of the most significant key elements in evaluating tunnel safety is the development of water pressure on the lining due to the deterioration of the drainage system. The increased water pressure on the lining is termed here as “residual water pressure”. The subsea tunnels generally need strict and careful monitoring of hydraulic effect to keep safe operation. Establishment of a well-organized maintenance program is therefore essential during operation. However，most aged-subsea tunnels do not have well-equipped monitoring systems，in addition even in new tunnels，the monitoring systems are often malfunctioned just after several years of operation. In this study，a new indirect and nondestructive method evaluating residual water pressure on the lining is proposed based on a characteristic water pressure curve obtained by numerical analysis. If the amount of water inflow，the height of water table and average ground permeability are known，the water pressures on the lining can be evaluated using the proposed analytical equations and the characteristic curves. It is shown that the method is particularly useful for tunnels of which measured data are not available and particularly for the aged-tunnels without monitoring systems. Applicability of the proposed method is illustrated by solving an example problem.

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EVALUATION OF RESIDUAL PORE WATER PRESSURES ON LININGS FOR UNDERSEA TUNNELS

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2007, 26 (S2): -3682 doi:
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[PDF 306 KB] (1019)

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Long-term observations for tunnels have shown two interesting aspects：an increase in leakage for watertight tunnels；and a decrease for leaking tunnels. An increase in leakage may exceed the capacity of drainage system and a decrease in leakage cause unexpected water pressure on the lining. Both excess leakage and additional water pressure are detrimental to running tunnels. Therefore，during tunnel operation，the flow behaviors around tunnel should be appropriately controlled. One of the most significant key elements in evaluating tunnel safety is the development of water pressure on the lining due to the deterioration of the drainage system. The increased water pressure on the lining is termed here as “residual water pressure”. The subsea tunnels generally need strict and careful monitoring of hydraulic effect to keep safe operation. Establishment of a well-organized maintenance program is therefore essential during operation. However，most aged-subsea tunnels do not have well-equipped monitoring systems，in addition even in new tunnels，the monitoring systems are often malfunctioned just after several years of operation. In this study，a new indirect and nondestructive method evaluating residual water pressure on the lining is proposed based on a characteristic water pressure curve obtained by numerical analysis. If the amount of water inflow，the height of water table and average ground permeability are known，the water pressures on the lining can be evaluated using the proposed analytical equations and the characteristic curves. It is shown that the method is particularly useful for tunnels of which measured data are not available and particularly for the aged-tunnels without monitoring systems. Applicability of the proposed method is illustrated by solving an example problem.

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GROUND PRESSURE ACTING ON CYLINDRICAL RETAINING WALL OF A SHAFT IN SOFT GROUND

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2007, 26 (S2): -3689 doi:
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A vertical shaft is a crucial part of underwater tunnel passing river or sea. A vertical shaft in a slender shape should be designed in different manners compared with the longitudinally slender structures such as tunnels. In the aspect of cross-section，the shaft is generally designed in a circular shape in spite of the fact that the rectangular type has more versatile usage of space. Besides，when a structure is constructed under river or sea，the open caissons designed in circular shape are adopted as for the foundation of the structures. However，this is outweighed by far the considerable advantages offered by the reduction of external pressure due to the arching effects in a horizontal plane. The wall stiffness，construction method and construction management during the construction of the support walls have an effect on the amount of wall displacement. In addition，development of cut wall displacement is essential even if the rigid lateral support such as a slurry wall is installed. Therefore，it has been recognized that the ground pressure on the cylindrical retaining wall is between the at-rest and active ground pressures under plane strain condition because of the stress relief，horizontal and vertical arching effects during excavation. The ground pressure distribution and the shape of failure surface by conducting model tests for the cylindrical retaining wall of a shaft in cohesionless soils are discussed.

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GROUND PRESSURE ACTING ON CYLINDRICAL RETAINING WALL OF A SHAFT IN SOFT GROUND

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2007, 26 (S2): -3689 doi:
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[PDF 305 KB] (2419)

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A vertical shaft is a crucial part of underwater tunnel passing river or sea. A vertical shaft in a slender shape should be designed in different manners compared with the longitudinally slender structures such as tunnels. In the aspect of cross-section，the shaft is generally designed in a circular shape in spite of the fact that the rectangular type has more versatile usage of space. Besides，when a structure is constructed under river or sea，the open caissons designed in circular shape are adopted as for the foundation of the structures. However，this is outweighed by far the considerable advantages offered by the reduction of external pressure due to the arching effects in a horizontal plane. The wall stiffness，construction method and construction management during the construction of the support walls have an effect on the amount of wall displacement. In addition，development of cut wall displacement is essential even if the rigid lateral support such as a slurry wall is installed. Therefore，it has been recognized that the ground pressure on the cylindrical retaining wall is between the at-rest and active ground pressures under plane strain condition because of the stress relief，horizontal and vertical arching effects during excavation. The ground pressure distribution and the shape of failure surface by conducting model tests for the cylindrical retaining wall of a shaft in cohesionless soils are discussed.

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NUMERICAL STUDY ON HORIZONTAL PRE-DRAINAGE SYSTEM USING HORIZONTAL DIRECTIONAL DRILLING IN SUBSEA TUNNELLING

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2007, 26 (S2): -3697 doi:
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[PDF 391 KB] (652)

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An effective pre-drainage system in a limited area that has a high water head and huge inflow is important to prevent flooding accidents during subsea tunnelling. Most of collapses in subsea tunnels are associated with huge inrushes of water due to high water head and flows through faults. To find out the causes and countermeasures for flooding cases，a dozen of cases for TBM and NATM tunneling are studied. Case studies presented here show that if the leakage had been forecasted and pre-drained prior to the tunnel excavation，such accidents could have been prevented. In this study，a new horizontal pre-drainage system is suggested. Numerical analyses are performed to analyze the water head controlling effect on the tunnel face by drainage holes during the construction of subsea tunnels. It is supposed that the rock cover of a subsea tunnel is 100 m，and the depth of seawater is 60 m. Drainage system analyses are performed to analyze performance of the drainage system. The total head after horizontal pre-drainages，when the permeability of the ground is 0.0036 m/h，reduces to about 60% at the tunnel crown and 53% at the tunnel spring line. When the radius of the drainage pipe is 5 cm and the permeability of the ground is 0.0036 m/h，the length of the pipe should not exceed 250 m to maintain the drainage performance. Numerical analysis and a drainage performance analysis both show that the suggested horizontal pre-drainage system provides a clear drainage and water head reducing effect. The system is a new alternative to the present water controlling methods applied to subsea tunnels.

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NUMERICAL STUDY ON HORIZONTAL PRE-DRAINAGE SYSTEM USING HORIZONTAL DIRECTIONAL DRILLING IN SUBSEA TUNNELLING

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2007, 26 (S2): -3697 doi:
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[PDF 260 KB] (1471)

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Show Abstract

An effective pre-drainage system in a limited area that has a high water head and huge inflow is important to prevent flooding accidents during subsea tunnelling. Most of collapses in subsea tunnels are associated with huge inrushes of water due to high water head and flows through faults. To find out the causes and countermeasures for flooding cases，a dozen of cases for TBM and NATM tunneling are studied. Case studies presented here show that if the leakage had been forecasted and pre-drained prior to the tunnel excavation，such accidents could have been prevented. In this study，a new horizontal pre-drainage system is suggested. Numerical analyses are performed to analyze the water head controlling effect on the tunnel face by drainage holes during the construction of subsea tunnels. It is supposed that the rock cover of a subsea tunnel is 100 m，and the depth of seawater is 60 m. Drainage system analyses are performed to analyze performance of the drainage system. The total head after horizontal pre-drainages，when the permeability of the ground is 0.0036 m/h，reduces to about 60% at the tunnel crown and 53% at the tunnel spring line. When the radius of the drainage pipe is 5 cm and the permeability of the ground is 0.0036 m/h，the length of the pipe should not exceed 250 m to maintain the drainage performance. Numerical analysis and a drainage performance analysis both show that the suggested horizontal pre-drainage system provides a clear drainage and water head reducing effect. The system is a new alternative to the present water controlling methods applied to subsea tunnels.

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PIPE SHIELD EFFECT ANALYSIS OF DOUBLE-ARCHED TUNNEL UNDER UNSYMMETRICAL PRESSURES

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2007, 26 (S2): -3704 doi:
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[PDF 416 KB] (938)

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Under the complex geological conditions of seabed，the pressure on surrounding rock of shallow double-arched tunnel is usually unsymmetrical，especially when the tunnel is connected to land and surrounded by soft rock. Consequently，the stability of the surrounding rock will be affected by the unsymmetrical pressures. In this paper，the pre-support function of pipe shield on unsymmetrical pressure section of double-arched tunnel was analyzed by using three-dimensional elasto-plastic contact finite difference method. The calculation results with different parameters of the pipe shield or tunnels were compared to analyze the effect of pipe shield. The mainly numerical results include：(1) the plastic zone and crown subsidence of the tunnel with/without pipe shield were simulated，respectively；(2) comparison of the deformation and moment of pipe shield according to design parameters or optimized parameters of pipe shield is conducted；and (3) comparison of crown subsidence and horizontal convergence displacement of FEM results with the corresponding item of actual measured results is performed. Pipe shield and grouting-reinforced rock can reduce the plastic zone around tunnel caused by unsymmetrical pressures effectively and it is necessary for double-arched tunnel in soft rock under unsymmetrical pressures to adopt pipe shield pre-support. Unsymmetrical pressures usually bring different stresses to lateral cavities of tunnel and the deformation of surrounding rock is uniform. Unbalanced design should be adopted for pipe shield in order that the deformation and stress can be controlled effectively. The result of numerical simulation is in accordance with the actually measured data，and it is proven that optical design of pipe shield is reasonable.

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PIPE SHIELD EFFECT ANALYSIS OF DOUBLE-ARCHED TUNNEL UNDER UNSYMMETRICAL PRESSURES

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2007, 26 (S2): -3704 doi:
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[PDF 539 KB] (1003)

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Under the complex geological conditions of seabed，the pressure on surrounding rock of shallow double-arched tunnel is usually unsymmetrical，especially when the tunnel is connected to land and surrounded by soft rock. Consequently，the stability of the surrounding rock will be affected by the unsymmetrical pressures. In this paper，the pre-support function of pipe shield on unsymmetrical pressure section of double-arched tunnel was analyzed by using three-dimensional elasto-plastic contact finite difference method. The calculation results with different parameters of the pipe shield or tunnels were compared to analyze the effect of pipe shield. The mainly numerical results include：(1) the plastic zone and crown subsidence of the tunnel with/without pipe shield were simulated，respectively；(2) comparison of the deformation and moment of pipe shield according to design parameters or optimized parameters of pipe shield is conducted；and (3) comparison of crown subsidence and horizontal convergence displacement of FEM results with the corresponding item of actual measured results is performed. Pipe shield and grouting-reinforced rock can reduce the plastic zone around tunnel caused by unsymmetrical pressures effectively and it is necessary for double-arched tunnel in soft rock under unsymmetrical pressures to adopt pipe shield pre-support. Unsymmetrical pressures usually bring different stresses to lateral cavities of tunnel and the deformation of surrounding rock is uniform. Unbalanced design should be adopted for pipe shield in order that the deformation and stress can be controlled effectively. The result of numerical simulation is in accordance with the actually measured data，and it is proven that optical design of pipe shield is reasonable.

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GROUTING TEST ON WATER-ENRICHED SAND LAYER OF XIAMEN XIANG¢AN SUBSEA TUNNEL

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2007, 26 (S2): -3711 doi:
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[PDF 266 KB] (708)

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Water-enriched sand layer will bring difficulty for grouting and therein result in failure of grouting. The influence of the seawater increases the difficulty of grouting. This paper presents grouting in water-enriched sand layer of the first subsea tunnel—Xiamen Xiang¢an subsea tunnel，China. Drilling and pushing water are used to check the grouting result. Some grouting rules are obtained and some parameters such as grouting amount，grouting pressure，grouting speed and diffusion radius are suggested. This paper also finds the results of an experimental investigation applied to the study of the effects of seawater. The result indicates that the seawater will delay the time of initial setting，slowing down the speed of gain in strength，diluting the density of slurry and aggravating differential pervasion of grouting. Several problems of grouting in seawater are discussed from the test and the construction experiences of Xiamen Xiang¢an subsea tunnel. The study can provide instructional advice for both design and construction of grouting of the Xiang¢an subsea tunnel. Meanwhile it can also provide important reference to similar project.

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GROUTING TEST ON WATER-ENRICHED SAND LAYER OF XIAMEN XIANG¢AN SUBSEA TUNNEL

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2007, 26 (S2): -3711 doi:
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[PDF 266 KB] (810)

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Show Abstract

Water-enriched sand layer will bring difficulty for grouting and therein result in failure of grouting. The influence of the seawater increases the difficulty of grouting. This paper presents grouting in water-enriched sand layer of the first subsea tunnel—Xiamen Xiang¢an subsea tunnel，China. Drilling and pushing water are used to check the grouting result. Some grouting rules are obtained and some parameters such as grouting amount，grouting pressure，grouting speed and diffusion radius are suggested. This paper also finds the results of an experimental investigation applied to the study of the effects of seawater. The result indicates that the seawater will delay the time of initial setting，slowing down the speed of gain in strength，diluting the density of slurry and aggravating differential pervasion of grouting. Several problems of grouting in seawater are discussed from the test and the construction experiences of Xiamen Xiang¢an subsea tunnel. The study can provide instructional advice for both design and construction of grouting of the Xiang¢an subsea tunnel. Meanwhile it can also provide important reference to similar project.

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SAFETY RISK ANALYSIS AND ASSESSMENT OF COMPLEX BUILDINGS IN SHALLOW-BURIED LARGE-SPAN TUNNEL CONSTRUCTION

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2007, 26 (S2): -3718 doi:
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[PDF 425 KB] (812)

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Increasing attention to urban environment safety due to urban tunnel excavation is focused in recent years. Therefore，it is significant to minimize the impact of tunnel construction on existing structures，facilities and especially some buildings. Compared with other structures，buildings are more sensitive to external effects because of particularity and complexity of structure；and their deformation mechanisms are more complicated，thus the accident consequences are more serious correspondingly. The 1st-stage Xiamen Airdrome project passes through a large number of buildings with shallow-buried large-span tunnel in complex geology strata，making the buildings protection crucial to assure environment safety and successful tunneling. Consequently，the mechanism and factors of tunneling-induced influence on buildings should be analyzed first，and then，after foundation and structure type，height and current damage condition，etc.，are classified，the safety evaluation of all the 63 buildings is then performed. Fuzzy-synthetic evaluation method is introduced in risk assessment and rating here. Nine key affecting factors of two general kinds are selected and the member function and weight of these factors are also determined. It is predicted that anticipated safety target of these buildings of different risk levels could be achieved with this specific guiding meaning.

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SAFETY RISK ANALYSIS AND ASSESSMENT OF COMPLEX BUILDINGS IN SHALLOW-BURIED LARGE-SPAN TUNNEL CONSTRUCTION

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2007, 26 (S2): -3718 doi:
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[PDF 425 KB] (851)

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Show Abstract

Increasing attention to urban environment safety due to urban tunnel excavation is focused in recent years. Therefore，it is significant to minimize the impact of tunnel construction on existing structures，facilities and especially some buildings. Compared with other structures，buildings are more sensitive to external effects because of particularity and complexity of structure；and their deformation mechanisms are more complicated，thus the accident consequences are more serious correspondingly. The 1st-stage Xiamen Airdrome project passes through a large number of buildings with shallow-buried large-span tunnel in complex geology strata，making the buildings protection crucial to assure environment safety and successful tunneling. Consequently，the mechanism and factors of tunneling-induced influence on buildings should be analyzed first，and then，after foundation and structure type，height and current damage condition，etc.，are classified，the safety evaluation of all the 63 buildings is then performed. Fuzzy-synthetic evaluation method is introduced in risk assessment and rating here. Nine key affecting factors of two general kinds are selected and the member function and weight of these factors are also determined. It is predicted that anticipated safety target of these buildings of different risk levels could be achieved with this specific guiding meaning.

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STRUCTURAL INTERNAL FORCE ANALYSIS OF ROCK SHIELD TUNNEL UNDER HIGH WATER PRESSURE DURING CONSTRUCTION

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2007, 26 (S2): -3727 doi:
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[PDF 389 KB] (544)

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There are many hot issues about solid-fluid coupling during the construction of large-scale shield tunnel beneath river or sea. The solid-fluid coupling effect on segments internal force in the process tunnel excavation is the main issue. According to the continuum theory，finite element analysis is adopted for a drain tunnel project crossing Yangtze River in the downtown of Chongqing City. Study on segment internal force distributing by two methods is carried out. One is considering water load combined with soil load，another is considering coupled effects. The result is verified by in-situ data. The calculation results show that internal forces of segments are different during shield tunnel construction. The internal forces of segments reach maximum values at the time of assemble completed，while the value will decrease for the long-term groundwater seepage. Mechanical characteristics of segment and structure are also studied，and shield tunnel construction parameters have close relationship with solid-fluid coupling. The achieved results can provide references to the design and construction of similar engineering cases.

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STRUCTURAL INTERNAL FORCE ANALYSIS OF ROCK SHIELD TUNNEL UNDER HIGH WATER PRESSURE DURING CONSTRUCTION

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2007, 26 (S2): -3727 doi:
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[PDF 389 KB] (711)

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There are many hot issues about solid-fluid coupling during the construction of large-scale shield tunnel beneath river or sea. The solid-fluid coupling effect on segments internal force in the process tunnel excavation is the main issue. According to the continuum theory，finite element analysis is adopted for a drain tunnel project crossing Yangtze River in the downtown of Chongqing City. Study on segment internal force distributing by two methods is carried out. One is considering water load combined with soil load，another is considering coupled effects. The result is verified by in-situ data. The calculation results show that internal forces of segments are different during shield tunnel construction. The internal forces of segments reach maximum values at the time of assemble completed，while the value will decrease for the long-term groundwater seepage. Mechanical characteristics of segment and structure are also studied，and shield tunnel construction parameters have close relationship with solid-fluid coupling. The achieved results can provide references to the design and construction of similar engineering cases.

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EFFECT OF DEWATERING WITH WELLS ON CONSTRUCTION OF SUBSEA TUNNEL WITH LARGE CROSS-SECTION

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2007, 26 (S2): -3732 doi:
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[PDF 358 KB] (611)

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Xiamen East Passage subsea tunnel is the first subsea tunnel with large cross-section in China，and its geological conditions are complex and unfavorable with enriched groundwater. The deformation of tunnel support in the entrance of Xiang¢an part is great. To reinforce the surrounding rock and reduce the effects of groundwater，the constructor dewaters the water level with wells based on in-situ experiences of similar engineering. To ascertain the effect of dewatering with wells，the parameters of wall rock by field experiment，i.e. disassemble experiment，shear experiment，are gained；and then，the construction safety was calculated with numerical analysis. Finally，the effects of the dewatering wells were achieved with the results of numerical analysis and locally measured data. The effects are mainly shown as follows：the arch-crown settlement of tunnel will be decreased to 50%，that of and horizontal convergence will be decreased to 30% after considering the dewatering wells；meanwhile，the range of plastic area also will be reduced to large extent，and the tunnel support safety will be increased.

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EFFECT OF DEWATERING WITH WELLS ON CONSTRUCTION OF SUBSEA TUNNEL WITH LARGE CROSS-SECTION

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2007, 26 (S2): -3732 doi:
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[PDF 358 KB] (715)

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Show Abstract

Xiamen East Passage subsea tunnel is the first subsea tunnel with large cross-section in China，and its geological conditions are complex and unfavorable with enriched groundwater. The deformation of tunnel support in the entrance of Xiang¢an part is great. To reinforce the surrounding rock and reduce the effects of groundwater，the constructor dewaters the water level with wells based on in-situ experiences of similar engineering. To ascertain the effect of dewatering with wells，the parameters of wall rock by field experiment，i.e. disassemble experiment，shear experiment，are gained；and then，the construction safety was calculated with numerical analysis. Finally，the effects of the dewatering wells were achieved with the results of numerical analysis and locally measured data. The effects are mainly shown as follows：the arch-crown settlement of tunnel will be decreased to 50%，that of and horizontal convergence will be decreased to 30% after considering the dewatering wells；meanwhile，the range of plastic area also will be reduced to large extent，and the tunnel support safety will be increased.

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SUBSIDENCE AND DEFORMATION CONTROL OF LARGE-SPAN TUNNEL IN WATER-BEARING UNFAVORABLE GEOLOGICAL CONDITIONS
WITH CRD METHOD

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2007, 26 (S2): -3738 doi:
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[PDF 262 KB] (737)

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：The land section with long distance in water-bearing unfavorable geological condition of Xiamen Xiang¢an subsea tunnel under construction was performed by center cross diagram(CRD) method. In order to ensure both safety and efficiency of construction，a study based on both numerical calculation and displacements measured in field was carried out. The arch-crown subsidence of CRD under different excavation sequences of headings and the distribution proportion of each heading excavation were discussed. Both calculation and field measured results indicated that，about 40% arch-crown subsidence was caused by excavation of heading 1；the arch-crown subsidence vs. time normally was in a shape of uplifted steps with a final stable value. An integral subsidence of tunnel less than 10% of final value occurred after primary lining was completed. Closing the inverted arch as soon as possible could greatly reduce the final subsidence. The space between border upon headings should be well controlled normally not more than 10–15 m，and the temporary inverted arch should be installed as soon as possible to form the lining structure.

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SUBSIDENCE AND DEFORMATION CONTROL OF LARGE-SPAN TUNNEL IN WATER-BEARING UNFAVORABLE GEOLOGICAL CONDITIONS
WITH CRD METHOD

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2007, 26 (S2): -3738 doi:
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[PDF 262 KB] (842)

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Show Abstract

The land section with long distance in water-bearing unfavorable geological condition of Xiamen Xiang¢an subsea tunnel under construction was performed by center cross diagram(CRD) method. In order to ensure both safety and efficiency of construction，a study based on both numerical calculation and displacements measured in field was carried out. The arch-crown subsidence of CRD under different excavation sequences of headings and the distribution proportion of each heading excavation were discussed. Both calculation and field measured results indicated that，about 40% arch-crown subsidence was caused by excavation of heading 1；the arch-crown subsidence vs. time normally was in a shape of uplifted steps with a final stable value. An integral subsidence of tunnel less than 10% of final value occurred after primary lining was completed. Closing the inverted arch as soon as possible could greatly reduce the final subsidence. The space between border upon headings should be well controlled normally not more than 10–15 m，and the temporary inverted arch should be installed as soon as possible to form the lining structure.

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DISCUSSION ON CONSTRUCTION SCHEMES FOR XIAMEN SUBSEA TUNNEL RIGHT LINE CROSSING WEATHERED SLOT F1

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2007, 26 (S2): -3743 doi:
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[PDF 410 KB] (601)

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In Tender A2 of right line of Xiamen Xiang¢an subsea tunnel，weathered slot F1 is needed to cross through. The feasible tunnel construction scheme to cross F1 weathered slot is important to the subsea tunnel construction. The subsea tunnel project has characteristics of difficult construction，limited construction time，large construction risk and higher construction quality. With consideration of Xiamen Xiang¢an subsea tunnel engineering geology characteristics，the general construction scheme for crossing through weathered slot F1 is proposed. The emphasis is made on the prediction and investigation of engineering geology，the rock mass excavation and lining scheme，the curtain grouting，the construction drainage system，the tunnel lining construction and the preparation scheme. The TSP203 geology prediction method is applied to the approach of the weathered slot F1，which gives guidance to determine the strength parameters of rock mass and underwater pressure. The improved double-side guiding whole tunnel-lining scheme is proposed to replace the original tunnel-lining scheme. Both the advantages and disadvantages of the improved tunnel-lining scheme are discussed. The rock grouting method is used to strengthen the rock mass from water permeation. Grouting schemes for the left and right guided holes，the guidance holes strengthening region and the forward grouting for central hole are discussed. The drainage system is illustrated，and the drainage system location，waterproof strobe are presented. The detailed construction scheme for crossing weathered slot F1 is proposed，which can provide some references to the engineering case.

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DISCUSSION ON CONSTRUCTION SCHEMES FOR XIAMEN SUBSEA TUNNEL RIGHT LINE CROSSING WEATHERED SLOT F1

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2007, 26 (S2): -3743 doi:
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[PDF 410 KB] (833)

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In Tender A2 of right line of Xiamen Xiang¢an subsea tunnel，weathered slot F1 is needed to cross through. The feasible tunnel construction scheme to cross F1 weathered slot is important to the subsea tunnel construction. The subsea tunnel project has characteristics of difficult construction，limited construction time，large construction risk and higher construction quality. With consideration of Xiamen Xiang¢an subsea tunnel engineering geology characteristics，the general construction scheme for crossing through weathered slot F1 is proposed. The emphasis is made on the prediction and investigation of engineering geology，the rock mass excavation and lining scheme，the curtain grouting，the construction drainage system，the tunnel lining construction and the preparation scheme. The TSP203 geology prediction method is applied to the approach of the weathered slot F1，which gives guidance to determine the strength parameters of rock mass and underwater pressure. The improved double-side guiding whole tunnel-lining scheme is proposed to replace the original tunnel-lining scheme. Both the advantages and disadvantages of the improved tunnel-lining scheme are discussed. The rock grouting method is used to strengthen the rock mass from water permeation. Grouting schemes for the left and right guided holes，the guidance holes strengthening region and the forward grouting for central hole are discussed. The drainage system is illustrated，and the drainage system location，waterproof strobe are presented. The detailed construction scheme for crossing weathered slot F1 is proposed，which can provide some references to the engineering case.

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LIMIT ANALYSIS OF SUBSEA TUNNEL STABILITY BY FINITE ELEMENT METHOD IN FAULT-RUPTURE ZONE WITH WATER PENETRATION

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2007, 26 (S2): -3751 doi:
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[PDF 222 KB] (658)

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Considering the sea water seepage，limit analysis by finite element method is used to study the stability of a subsea tunnel in which the fracture zone exists. Result shows that the tunnel is safe for the intact surrounding rock. Under the condition，the lining of the subsea tunnel can be designed without water pressure；and the lining thickness can be reduced remarkably. The calculation results show that the fault-rupture zone decreases the stability of tunnel obviously. The wider the fracture zone is，the smaller the safety factor is. The thicker the rock grouting ring is，the larger the safety factor is. Slip surface of intact surrounding rock appears at both sides of tunnel；and the stability of rock mass in fracture zone with angle of 45°is the most unfavorable. So the pregrouting treatment is necessary in order to cut down the seepage water. Under this condition，the tunnel lining can be designed according to principle with water pressure.

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LIMIT ANALYSIS OF SUBSEA TUNNEL STABILITY BY FINITE ELEMENT METHOD IN FAULT-RUPTURE ZONE WITH WATER PENETRATION

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2007, 26 (S2): -3751 doi:
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[PDF 222 KB] (796)

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Considering the sea water seepage，limit analysis by finite element method is used to study the stability of a subsea tunnel in which the fracture zone exists. Result shows that the tunnel is safe for the intact surrounding rock. Under the condition，the lining of the subsea tunnel can be designed without water pressure；and the lining thickness can be reduced remarkably. The calculation results show that the fault-rupture zone decreases the stability of tunnel obviously. The wider the fracture zone is，the smaller the safety factor is. The thicker the rock grouting ring is，the larger the safety factor is. Slip surface of intact surrounding rock appears at both sides of tunnel；and the stability of rock mass in fracture zone with angle of 45°is the most unfavorable. So the pregrouting treatment is necessary in order to cut down the seepage water. Under this condition，the tunnel lining can be designed according to principle with water pressure.

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PRELIMINARY RESEARCH ON SAFETY EVALUATION FOR SUBSEA TUNNEL CONSTRUCTION

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2007, 26 (S2): -3756 doi:
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[PDF 284 KB] (743)

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Due to the polytrope and uncertainty of geological conditions，there are many risk ources in the construction of tunnel and underground projects，especially for subsea tunnel construction. Up to now，there is a proper method for safety evaluation of subsea tunnel construction. Based on the risk analysis，the risk sources have been identified. Combining with the experiences in the safe construction of tunnel and underground engineering，based on the classification of rock mass，the achievements in rock mechanics and measuring techniques，and the research experiences in safety evaluation，a safety evaluation system for subsea tunnel construction is established. The main relevant factors and their weight coefficients directly influencing the construction safety of subsea tunnel are given. Accordingly a system with six ranks from I to VI is put forward. The evaluation method put forward above has been applied to a practical engineering. The results show that the safety evaluation result is closed to the practical one.

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PRELIMINARY RESEARCH ON SAFETY EVALUATION FOR SUBSEA TUNNEL CONSTRUCTION

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2007, 26 (S2): -3756 doi:
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[PDF 284 KB] (685)

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Due to the polytrope and uncertainty of geological conditions，there are many risk ources in the construction of tunnel and underground projects，especially for subsea tunnel construction. Up to now，there is a proper method for safety evaluation of subsea tunnel construction. Based on the risk analysis，the risk sources have been identified. Combining with the experiences in the safe construction of tunnel and underground engineering，based on the classification of rock mass，the achievements in rock mechanics and measuring techniques，and the research experiences in safety evaluation，a safety evaluation system for subsea tunnel construction is established. The main relevant factors and their weight coefficients directly influencing the construction safety of subsea tunnel are given. Accordingly a system with six ranks from I to VI is put forward. The evaluation method put forward above has been applied to a practical engineering. The results show that the safety evaluation result is closed to the practical one.

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STUDY ON MECHANICAL DISTRIBUTION CHARACTERISTIC OF LINING STRUCTURE INFLUENCED BY SEGMENT WIDTH FOR WUHAN YANGTZE RIVER TUNNEL

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2007, 26 (S2): -3763 doi:
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[PDF 296 KB] (807)

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Taking the Wuhan Yangtze River tunnel as an engineering background，the 3D mechanical distribution characteristic of lining whose segment width ranges from 1 to 10 m is analyzed by establishing a 3D shell-nonlinear spring model which needs to input the nonlinear data about bending moment，axial force and rotating angle of segment joint. The analytical results about internal forces are contrasted with those calculated by traditional beam-nonlinear spring model. In addition，the internal force distribution rules of segment lining structure influenced by segment width are achieved. Finally，the rules are validated primarily by large-scale similar model test. The study shows that：(1) both the positive and the negative maximum bending moments of the 3D lining structure always occur on the edge of segment；(2) the maximum bending moment calculated by the beam-nonlinear spring model equals to that calculated by 3D shell-spring model on the edge of segment when it is assumed that the shear stiffness between rings is infinite，which indicates that using the results obtained by beam-nonlinear spring model to analyze lining structure is safe；(3) in the middle of the segment，the maximum bending moment calculated by the beam-nonlinear spring model is greater than that calculated by 3D shell-nonlinear model，so the reinforcement ratio of reinforced concrete in the middle of segment obtained by the beam-nonlinear spring model is greater than that by 3D shell-nonlinear spring model；and (4) the radial shear force on the ring joint calculated by the 3D shell-nonlinear spring model is less than that induced by the beam-nonlinear spring model，the larger the segment width is，the bigger the margin between them is. The study results can provide valuable references to reinforcement design of segment structure in the shield tunnel under the big river or sea and security appraisal of segment lining.

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STUDY ON MECHANICAL DISTRIBUTION CHARACTERISTIC OF LINING STRUCTURE INFLUENCED BY SEGMENT WIDTH FOR WUHAN YANGTZE RIVER TUNNEL

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2007, 26 (S2): -3763 doi:
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[PDF 296 KB] (804)

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Taking the Wuhan Yangtze River tunnel as an engineering background，the 3D mechanical distribution characteristic of lining whose segment width ranges from 1 to 10 m is analyzed by establishing a 3D shell-nonlinear spring model which needs to input the nonlinear data about bending moment，axial force and rotating angle of segment joint. The analytical results about internal forces are contrasted with those calculated by traditional beam-nonlinear spring model. In addition，the internal force distribution rules of segment lining structure influenced by segment width are achieved. Finally，the rules are validated primarily by large-scale similar model test. The study shows that：(1) both the positive and the negative maximum bending moments of the 3D lining structure always occur on the edge of segment；(2) the maximum bending moment calculated by the beam-nonlinear spring model equals to that calculated by 3D shell-spring model on the edge of segment when it is assumed that the shear stiffness between rings is infinite，which indicates that using the results obtained by beam-nonlinear spring model to analyze lining structure is safe；(3) in the middle of the segment，the maximum bending moment calculated by the beam-nonlinear spring model is greater than that calculated by 3D shell-nonlinear model，so the reinforcement ratio of reinforced concrete in the middle of segment obtained by the beam-nonlinear spring model is greater than that by 3D shell-nonlinear spring model；and (4) the radial shear force on the ring joint calculated by the 3D shell-nonlinear spring model is less than that induced by the beam-nonlinear spring model，the larger the segment width is，the bigger the margin between them is. The study results can provide valuable references to reinforcement design of segment structure in the shield tunnel under the big river or sea and security appraisal of segment lining.

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NEW ELASTOPLASTIC SOLUTIONS TO CIRCULAR PRESSURED TUNNEL WITH LINING

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2007, 26 (S2): -3770 doi:
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[PDF 288 KB] (684)

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The elastoplastic problem for circular pressured tunnel with lining is investigated. Firstly，an appropriate mechanical model considering the stress relief and the installation sequence of the lining is proposed to model the construction sequence of the tunnel structure. Next，by applying the series of expansion technologies in the complex theory established by Muskhelishvili，the complex stress functions are properly presented. Then，considering the continuity conditions for the stress and displacement along the boundary，in conjunction with the comparisons of the same power exponent on both sides of the equality，the presented problem is reduced to solve a set of linear algebraic equations. Sequentially，the complex potentials in the lining and the surrounding rock are explicitly derived respectively. Finally，based on the linear Mohr-Coulomb yield criterion，for two cases that the first principal stress is the radial stress or the tangential stress respectively，with consideration of boundary conditions along the internal and external boundaries of the lining and the interface between the elastic and plastic regions，the stress solutions for the total field are given when the interface between the elastic and plastic regions is in the lining. The presented solutions contain previously known results as the special cases，for example，classical Fenner¢s solution and Savin¢s solution.

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NEW ELASTOPLASTIC SOLUTIONS TO CIRCULAR PRESSURED TUNNEL WITH LINING

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2007, 26 (S2): -3770 doi:
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[PDF 288 KB] (729)

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The elastoplastic problem for circular pressured tunnel with lining is investigated. Firstly，an appropriate mechanical model considering the stress relief and the installation sequence of the lining is proposed to model the construction sequence of the tunnel structure. Next，by applying the series of expansion technologies in the complex theory established by Muskhelishvili，the complex stress functions are properly presented. Then，considering the continuity conditions for the stress and displacement along the boundary，in conjunction with the comparisons of the same power exponent on both sides of the equality，the presented problem is reduced to solve a set of linear algebraic equations. Sequentially，the complex potentials in the lining and the surrounding rock are explicitly derived respectively. Finally，based on the linear Mohr-Coulomb yield criterion，for two cases that the first principal stress is the radial stress or the tangential stress respectively，with consideration of boundary conditions along the internal and external boundaries of the lining and the interface between the elastic and plastic regions，the stress solutions for the total field are given when the interface between the elastic and plastic regions is in the lining. The presented solutions contain previously known results as the special cases，for example，classical Fenner¢s solution and Savin¢s solution.

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ANALYSIS OF SEEPAGE PROBLEM INDUCED BY SUBSEA TUNNEL EXCAVATION BASED ON CONTINUUM MEDIUM MODEL

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2007, 26 (S2): -3776 doi:
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[PDF 418 KB] (686)

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One of the most prominent characters of subsea tunnel is that there is enriched water body because of the infinitude of the ocean above. There are mainly about two seepage problems induced by subsea tunnel excavation：one is determination of seepage pressure，another is the water inflow. Isotropic continuum medium model is adopted to analyze these two problems mentioned above. The essential of water pressure is studied；and conclusions are drawn. According to the latest research，some analytical models which are based on steady-state groundwater inflow into a drained circular tunnel in a semi-infinite aquifer connected with water pressure and water inflow are compared. The subsea tunnel in Kiaochow Bay is taken as background of the study. The influence of stress filed on seepage field is studied；and the effects of changes of surrounding rock permeability coefficient，water depth，permeability coefficient and thickness of grouting ring are analyzed which can be adopted for this particular project. According to the research，the pore water pressure and water inflow induced by tunnel excavation can be hardly affected by arching effect. Without consideration of fluid-solid coupling effect，if keeping the water level above horizontal plane fixed，the distribution of pore water pressure will not change with permeability coefficient of surrounding rock. The water inflow increases with the change of permeability coefficient of surrounding rock or water depth above surrounding rock. Both the decrease of permeability coefficient and the increase of thickness of grouting ring can reduce ground water inflow，but there exists an optimal value in grouting parameters. In practice，the decision should be made carefully between economy and bulkhead effect to confirm the optimal grouting parameters.

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ANALYSIS OF SEEPAGE PROBLEM INDUCED BY SUBSEA TUNNEL EXCAVATION BASED ON CONTINUUM MEDIUM MODEL

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2007, 26 (S2): -3776 doi:
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[PDF 418 KB] (1158)

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Show Abstract

One of the most prominent characters of subsea tunnel is that there is enriched water body because of the infinitude of the ocean above. There are mainly about two seepage problems induced by subsea tunnel excavation：one is determination of seepage pressure，another is the water inflow. Isotropic continuum medium model is adopted to analyze these two problems mentioned above. The essential of water pressure is studied；and conclusions are drawn. According to the latest research，some analytical models which are based on steady-state groundwater inflow into a drained circular tunnel in a semi-infinite aquifer connected with water pressure and water inflow are compared. The subsea tunnel in Kiaochow Bay is taken as background of the study. The influence of stress filed on seepage field is studied；and the effects of changes of surrounding rock permeability coefficient，water depth，permeability coefficient and thickness of grouting ring are analyzed which can be adopted for this particular project. According to the research，the pore water pressure and water inflow induced by tunnel excavation can be hardly affected by arching effect. Without consideration of fluid-solid coupling effect，if keeping the water level above horizontal plane fixed，the distribution of pore water pressure will not change with permeability coefficient of surrounding rock. The water inflow increases with the change of permeability coefficient of surrounding rock or water depth above surrounding rock. Both the decrease of permeability coefficient and the increase of thickness of grouting ring can reduce ground water inflow，but there exists an optimal value in grouting parameters. In practice，the decision should be made carefully between economy and bulkhead effect to confirm the optimal grouting parameters.

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RESEARCH ON DESIGN OF SUBSEA TUNNEL STRUCTURAL HEALTH MONITORING

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2007, 26 (S2): -3785 doi:
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[PDF 402 KB] (988)

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：Due to the particular and complex engineering environment of subsea tunnel，the long-term structural health monitoring should be adopted to ensure the operation security of subsea tunnel. At the same time，stress change state of tunnel in complex environment will be realized. Then the damage position and damage degree of tunnel structure will be known in time for evaluating structure safety and disposing it effectively. For Xiamen Xiang¢an subsea tunnel，based on the present state generalization of tunnel structure health monitoring and characteristic of subsea tunnel engineering，the monitoring contents and important monitoring sites should be determined firstly according to necessary numerical simulation. Secondly，according to the practical situation of engineering，monitoring section positions，monitoring items and monitoring instruments will be selected. Besides，the following conclusions can be drawn. (1) To monitor the safety of tunnel in unfavorable geological area，except for the important site of tunnel，the auxiliary monitoring section should be also set up in adjacent and preferable geological conditions. Then it is very convenient to analyze the influence of unfavorable geological conditions on tunnel structure. (2) The leakage situation of subsea tunnel structure could be obtained by indirect monitoring results in main areas，such as arch lining cooperating change of lining water pressure in corresponding position. Issues mentioned above may have a guiding sense to the application of structural health monitoring of subsea tunnels under construction in China.

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RESEARCH ON DESIGN OF SUBSEA TUNNEL STRUCTURAL HEALTH MONITORING

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2007, 26 (S2): -3785 doi:
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[PDF 402 KB] (1395)

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Due to the particular and complex engineering environment of subsea tunnel，the long-term structural health monitoring should be adopted to ensure the operation security of subsea tunnel. At the same time，stress change state of tunnel in complex environment will be realized. Then the damage position and damage degree of tunnel structure will be known in time for evaluating structure safety and disposing it effectively. For Xiamen Xiang¢an subsea tunnel，based on the present state generalization of tunnel structure health monitoring and characteristic of subsea tunnel engineering，the monitoring contents and important monitoring sites should be determined firstly according to necessary numerical simulation. Secondly，according to the practical situation of engineering，monitoring section positions，monitoring items and monitoring instruments will be selected. Besides，the following conclusions can be drawn. (1) To monitor the safety of tunnel in unfavorable geological area，except for the important site of tunnel，the auxiliary monitoring section should be also set up in adjacent and preferable geological conditions. Then it is very convenient to analyze the influence of unfavorable geological conditions on tunnel structure. (2) The leakage situation of subsea tunnel structure could be obtained by indirect monitoring results in main areas，such as arch lining cooperating change of lining water pressure in corresponding position. Issues mentioned above may have a guiding sense to the application of structural health monitoring of subsea tunnels under construction in China.

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STATISTIC ANALYSIS OF STRATUM DEFORMATION DURING TUNNEL EXCAVATION

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2007, 26 (S2): -3793 doi:
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[PDF 294 KB] (1394)

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Based on the observed data of more than 70 shallow-depth-excavation tunnels，the formula for the maximum settlement of shallow-depth-excavation tunnel is deduced by analyzing all kinds of factors affecting stratum deformation. In addition，the law of stratum deformation is summarized. For example，the probability distributions of the maximum ground subsidence and the vault settlement appear to be approximately normal ones. With the decline of the stability of surrounding rock，the ground subsidence and the vault settlement increase gradually. When the tunnel span is between 5 and 10 m，the relationship between the maximum ground subsidence and the tunnel depth display convex shape with the surrounding rock of classes II，III，V. When the tunnel depth is less than 25 m，the maximum vault settlement increases with the rise of depth for tunnel with surrounding rock of classes II，III. The ratios of the vault settlement to the ground settlement are in the range of 0.5–1.5. When the depth of the tunnel is less than 20 m，the widths of the settlement trough are between 8R and 12R(R is equivalent radius). Finally，the collapse height，collapse amount are analyzed for more than 50 collapse tunnels. Furthermore，the main influential factors are discussed. The research results are of great importance and practical value to the design and construction of tunnel.

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STATISTIC ANALYSIS OF STRATUM DEFORMATION DURING TUNNEL EXCAVATION

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2007, 26 (S2): -3793 doi:
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[PDF 294 KB] (660)

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Based on the observed data of more than 70 shallow-depth-excavation tunnels，the formula for the maximum settlement of shallow-depth-excavation tunnel is deduced by analyzing all kinds of factors affecting stratum deformation. In addition，the law of stratum deformation is summarized. For example，the probability distributions of the maximum ground subsidence and the vault settlement appear to be approximately normal ones. With the decline of the stability of surrounding rock，the ground subsidence and the vault settlement increase gradually. When the tunnel span is between 5 and 10 m，the relationship between the maximum ground subsidence and the tunnel depth display convex shape with the surrounding rock of classes II，III，V. When the tunnel depth is less than 25 m，the maximum vault settlement increases with the rise of depth for tunnel with surrounding rock of classes II，III. The ratios of the vault settlement to the ground settlement are in the range of 0.5–1.5. When the depth of the tunnel is less than 20 m，the widths of the settlement trough are between 8R and 12R(R is equivalent radius). Finally，the collapse height，collapse amount are analyzed for more than 50 collapse tunnels. Furthermore，the main influential factors are discussed. The research results are of great importance and practical value to the design and construction of tunnel.

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STUDY ON STABILITY CONTROL OF LARGE-SECTION SUBSEA TUNNELS IN WEAK STRATA BY CRD CONSTRUCTION METHOD

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2007, 26 (S2): -3804 doi:
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[PDF 293 KB] (917)

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Combined with the facts that the strata of the entrance at Xiang¢an side of Xiamen Xiang¢an subsea tunnel are weak and unstable，the excavation is difficult，and the preliminary lining deforms severely. The reason of the left tunnel deformation excavated by CRD method under the condition of surrounding rock of class V is analyzed. Based on the measuring data，the construction stability of the large-section subsea tunnel in weak strata is analyzed，including the characters of surrounding rock，the distance between each step of CRD working face，the time of each step of CRD first shoring finished，the time of the whole working face completed，the distance between the permanent inverted arch and the working face，and grouting behind preliminary support or not. Based on these，the measures controlling the deformation are put forward. Successful practice and techniques are summarized to provide experiences for similar engineering.

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STUDY ON STABILITY CONTROL OF LARGE-SECTION SUBSEA TUNNELS IN WEAK STRATA BY CRD CONSTRUCTION METHOD

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2007, 26 (S2): -3804 doi:
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[PDF 293 KB] (950)

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Combined with the facts that the strata of the entrance at Xiang¢an side of Xiamen Xiang¢an subsea tunnel are weak and unstable，the excavation is difficult，and the preliminary lining deforms severely. The reason of the left tunnel deformation excavated by CRD method under the condition of surrounding rock of class V is analyzed. Based on the measuring data，the construction stability of the large-section subsea tunnel in weak strata is analyzed，including the characters of surrounding rock，the distance between each step of CRD working face，the time of each step of CRD first shoring finished，the time of the whole working face completed，the distance between the permanent inverted arch and the working face，and grouting behind preliminary support or not. Based on these，the measures controlling the deformation are put forward. Successful practice and techniques are summarized to provide experiences for similar engineering.

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STUDY ON WATERPROOF AND DRAINAGE PRINCIPLES OF XIAMEN SUBSEA TUNNEL

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2007, 26 (S2): -3810 doi:
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[PDF 304 KB] (673)

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Subsea tunnel is different from land tunnel with abundant water，high water pressure and without automatic drainage. These lead to more serious leakage problems，which are difficult to be dealt with comparison to land tunnel. Rationality and reliability of the waterproof and drainage system are the key factors for a successful subsea tunnel and the main parts controlling operation cost. The determination of waterproof and drainage principles is the basis for design of reasonable waterproof and drainage system. Based on the data of the existing subsea tunnels，the critical groundwater level is put up to determine waterproof and drainage principles. The water discharge and water pressure on lining with hidden pipe drainage system are calculated by numerical method for Xiamen subsea tunnel，and the feasibility of installation of drainage system is studied from point of view of economical efficiency during operation. The principle that blockage is dominant and drainage is limited is put forward for Xiamen subsea tunnel. Based on this，the reasonable waterproof and drainage system is brought forward and has been applied to this project. As the first systematic study for the first subsea tunnel with drill and blast method in China，the research method is a reference for other subsea tunnels.

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STUDY ON WATERPROOF AND DRAINAGE PRINCIPLES OF XIAMEN SUBSEA TUNNEL

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2007, 26 (S2): -3810 doi:
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[PDF 304 KB] (835)

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Show Abstract

Subsea tunnel is different from land tunnel with abundant water，high water pressure and without automatic drainage. These lead to more serious leakage problems，which are difficult to be dealt with comparison to land tunnel. Rationality and reliability of the waterproof and drainage system are the key factors for a successful subsea tunnel and the main parts controlling operation cost. The determination of waterproof and drainage principles is the basis for design of reasonable waterproof and drainage system. Based on the data of the existing subsea tunnels，the critical groundwater level is put up to determine waterproof and drainage principles. The water discharge and water pressure on lining with hidden pipe drainage system are calculated by numerical method for Xiamen subsea tunnel，and the feasibility of installation of drainage system is studied from point of view of economical efficiency during operation. The principle that blockage is dominant and drainage is limited is put forward for Xiamen subsea tunnel. Based on this，the reasonable waterproof and drainage system is brought forward and has been applied to this project. As the first systematic study for the first subsea tunnel with drill and blast method in China，the research method is a reference for other subsea tunnels.

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CONSTRUCTION TECHNIQUES OF XIAMEN XIANG¢AN SUBSEA TUNNEL ACROSS WATER-ENRICHED SANDY STRATUM

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2007, 26 (S2): -3816 doi:
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[PDF 416 KB] (585)

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Xiamen Xiang¢an subsea tunnel is the first subsea tunnel in mainland China，the length of which is
6 051 m. The length of the part of Xiamen Xiang¢an subsea tunnel in shallow beach is 610 m. There are no similar projects and experiences of construction for subsea tunnel to be referred. So the construction is difficult for the tunnel in shallow beach across the water-enriched sandy stratum. The key construction techniques for the tunnel across the water-enriched sandy stratum in shallow beach are introduced. The diaphragm wall and decompression well are used to resist and drain groundwater of sandy stratum. The ductule pre-grouting technology is used to reinforce sandy stratum in the tunnel. Integration of outside and inside construction technology of tunnel is adopted to cross the water-enriched sandy stratum in shallow beach. The practical result shows that the construction techniques are convenient and effective. The construction experiences are useful references to other underground engineering under similar geological conditions.

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CONSTRUCTION TECHNIQUES OF XIAMEN XIANG¢AN SUBSEA TUNNEL ACROSS WATER-ENRICHED SANDY STRATUM

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2007, 26 (S2): -3816 doi:
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[PDF 416 KB] (1096)

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Show Abstract

Xiamen Xiang¢an subsea tunnel is the first subsea tunnel in mainland China，the length of which is
6 051 m. The length of the part of Xiamen Xiang¢an subsea tunnel in shallow beach is 610 m. There are no similar projects and experiences of construction for subsea tunnel to be referred. So the construction is difficult for the tunnel in shallow beach across the water-enriched sandy stratum. The key construction techniques for the tunnel across the water-enriched sandy stratum in shallow beach are introduced. The diaphragm wall and decompression well are used to resist and drain groundwater of sandy stratum. The ductule pre-grouting technology is used to reinforce sandy stratum in the tunnel. Integration of outside and inside construction technology of tunnel is adopted to cross the water-enriched sandy stratum in shallow beach. The practical result shows that the construction techniques are convenient and effective. The construction experiences are useful references to other underground engineering under similar geological conditions.

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ENVIRONMENTAL CONDITION AND DURABILITY OF LINING CONCRETE IN KIAOCHOW BAY SUBSEA TUNNEL

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2007, 26 (S2): -3823 doi:
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[PDF 383 KB] (872)

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The Kiaochow Bay subsea tunnel locates at Kulong Mountain between Tuandao in Shinan District and Xuejia Island in Huangdao District. The area where the tunnel entrance lies is surrounded by large area of seawater. The content of chloride ion in the air near the air-inlet and the entrance of the tunnel is high. Therefore，the areas where the air-inlet and the entrance of the tunnel stand belong to the severe salt mist areas. The monthly average temperature in Qingdao recently is 0 ℃–24 ℃. There are about 90 days in a year when the lowest temperature is below zero. So the lining concrete close to the exits will suffer freeze-thaw cycles. The lining concrete in the tunnel tends to be fractured due to wet-dry cycles. The monthly average relative humidity in Qingdao is between 62% and 86%. So the concrete carbonation takes place faster. Under common transportation and ventilation conditions，the content of CO2 in the air in the tunnel or close to the exits is at least five times of that in atmosphere，where concrete carbonation needs to be considered. ，K+ and Na+ in seawater or underground water can lead to concrete sulphate corrosion and alkali-aggregate action. Therefore，alkali-aggregate action，chloride ion penetration，sulphate corrosion，carbonation，freeze-thaw，fire，and so on should be taken into occount in the durability design of the tunnel lining concrete. It should be stricted on the raw materials of concrete，mixture，properties，quality control，structure design，workmanship，and inspection standards. Furthermore，as the tunnel is an emportant project with 100 years service life，other measures such as concrete surface treatment and imbedded durability monitoring system should be considered. Experiment results show that the carbonation depth of concrete decreases with its increasing compressive strength；and the carbonation resistance capacity of concrete improves with increasing of cement amount and decreasing of w/b. Relationship between chloride ion diffusion coefficient and compressive strength is accordance with exponential function；and the chloride ion diffusion coefficient of concrete would be less than 4×10－12 m2/s when the concrete strength grade is higher than C50.

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ENVIRONMENTAL CONDITION AND DURABILITY OF LINING CONCRETE IN KIAOCHOW BAY SUBSEA TUNNEL

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2007, 26 (S2): -3823 doi:
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[PDF 383 KB] (935)

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The Kiaochow Bay subsea tunnel locates at Kulong Mountain between Tuandao in Shinan District and Xuejia Island in Huangdao District. The area where the tunnel entrance lies is surrounded by large area of seawater. The content of chloride ion in the air near the air-inlet and the entrance of the tunnel is high. Therefore，the areas where the air-inlet and the entrance of the tunnel stand belong to the severe salt mist areas. The monthly average temperature in Qingdao recently is 0 ℃–24 ℃. There are about 90 days in a year when the lowest temperature is below zero. So the lining concrete close to the exits will suffer freeze-thaw cycles. The lining concrete in the tunnel tends to be fractured due to wet-dry cycles. The monthly average relative humidity in Qingdao is between 62% and 86%. So the concrete carbonation takes place faster. Under common transportation and ventilation conditions，the content of CO2 in the air in the tunnel or close to the exits is at least five times of that in atmosphere，where concrete carbonation needs to be considered. ，K+ and Na+ in seawater or underground water can lead to concrete sulphate corrosion and alkali-aggregate action. Therefore，alkali-aggregate action，chloride ion penetration，sulphate corrosion，carbonation，freeze-thaw，fire，and so on should be taken into occount in the durability design of the tunnel lining concrete. It should be stricted on the raw materials of concrete，mixture，properties，quality control，structure design，workmanship，and inspection standards. Furthermore，as the tunnel is an emportant project with 100 years service life，other measures such as concrete surface treatment and imbedded durability monitoring system should be considered. Experiment results show that the carbonation depth of concrete decreases with its increasing compressive strength；and the carbonation resistance capacity of concrete improves with increasing of cement amount and decreasing of w/b. Relationship between chloride ion diffusion coefficient and compressive strength is accordance with exponential function；and the chloride ion diffusion coefficient of concrete would be less than 4×10－12 m2/s when the concrete strength grade is higher than C50.

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VALIDITY ANALYSIS OF LOCKING ANCHOR PIPE AND GROUTING IN INVERTED ARCH FOR DISPLACEMENT CONTROL OF LARGE-SECTION SUBSEA TUNNEL

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2007, 26 (S2): -3830 doi:
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[PDF 287 KB] (714)

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In land sections of Xiang¢an subsea tunnel in Xiamen with unfavorable geological condition，where large-section shallow-buried excavation method is adopted，the vault subsidence of some sections exceeds allowable value obviously. As the measured data in field show that the integral subsidence(including both during excavation of headings and after closure of primary lining) is an important factor leading to vault subsidence. Countermeasures including setting locking anchor pipes and grouting in inverted arch have been taken in field to control the settlement. In order to investigate the effect of different countermeasures，firstly，a numerical simulation is carried out based on physico-mechanical parameters of surrounding rock and lining structure provided by both design documentation and field test. And then a general analysis is carried out based on the numerical simulation and measured data in field. Results indicate that，after setting locking anchor pipes，vault subsidence can be reduced about 17 percent，and horizontal convergence 12 percent nearly；after grouting in inverted arch，vault subsidence can be reduced about 18 percent；both two countermeasures can reduce plastic area in surrounding rock and increase structure safety to a certain extent.

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VALIDITY ANALYSIS OF LOCKING ANCHOR PIPE AND GROUTING IN INVERTED ARCH FOR DISPLACEMENT CONTROL OF LARGE-SECTION SUBSEA TUNNEL

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2007, 26 (S2): -3830 doi:
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[PDF 287 KB] (869)

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In land sections of Xiang¢an subsea tunnel in Xiamen with unfavorable geological condition，where large-section shallow-buried excavation method is adopted，the vault subsidence of some sections exceeds allowable value obviously. As the measured data in field show that the integral subsidence(including both during excavation of headings and after closure of primary lining) is an important factor leading to vault subsidence. Countermeasures including setting locking anchor pipes and grouting in inverted arch have been taken in field to control the settlement. In order to investigate the effect of different countermeasures，firstly，a numerical simulation is carried out based on physico-mechanical parameters of surrounding rock and lining structure provided by both design documentation and field test. And then a general analysis is carried out based on the numerical simulation and measured data in field. Results indicate that，after setting locking anchor pipes，vault subsidence can be reduced about 17 percent，and horizontal convergence 12 percent nearly；after grouting in inverted arch，vault subsidence can be reduced about 18 percent；both two countermeasures can reduce plastic area in surrounding rock and increase structure safety to a certain extent.

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LINING STRUCTURE DESIGN OF SUBSEA TUNNEL

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2007, 26 (S2): -3835 doi:
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[PDF 272 KB] (716)

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The water above surrounding rock of subsea tunnel is of a stable water level with plentiful supply. The tunnel lining structure bears water pressure for long time. In design of lining structure，the water pressure should be identified firstly. The evaluation and calculation of tunnel cross-section layout，lining type and structure safety are carried out based on water pressure and water inflow. For Xiamen Xiang¢an subsea tunnel under construction，model test of the external water pressure feature under different drainage modes indicates that the water pressure on fully-enclosed lining should be not discounted. The water inflow in the tunnel is forecasted；and the lining is designed in fully-enclosed or limited drainage type since the drainage in operation stage can not be satisfied. The most economic and reasonable lining cross-section is obtained based on structure analysis and comparison under different lining sections with combination of water pressure and surrounding rock pressure by means of finite element software ANSYS. The recommended lining section is proven to be reasonable by both computing results and construction practice.

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LINING STRUCTURE DESIGN OF SUBSEA TUNNEL

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2007, 26 (S2): -3835 doi:
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[PDF 272 KB] (921)

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The water above surrounding rock of subsea tunnel is of a stable water level with plentiful supply. The tunnel lining structure bears water pressure for long time. In design of lining structure，the water pressure should be identified firstly. The evaluation and calculation of tunnel cross-section layout，lining type and structure safety are carried out based on water pressure and water inflow. For Xiamen Xiang¢an subsea tunnel under construction，model test of the external water pressure feature under different drainage modes indicates that the water pressure on fully-enclosed lining should be not discounted. The water inflow in the tunnel is forecasted；and the lining is designed in fully-enclosed or limited drainage type since the drainage in operation stage can not be satisfied. The most economic and reasonable lining cross-section is obtained based on structure analysis and comparison under different lining sections with combination of water pressure and surrounding rock pressure by means of finite element software ANSYS. The recommended lining section is proven to be reasonable by both computing results and construction practice.

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GROUTING TECHNOLOGY FOR WATER BLOCKAGE OF WEATHERED SLOT F1 IN XIAMEN XIANG¢AN SUBSEA SERVICE TUNNEL

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2007, 26 (S2): -3841 doi:
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[PDF 413 KB] (608)

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Xiamen Xiang¢an subsea tunnel，with the total length of 5.948 km，is the first subsea tunnel designed and constructed by mainland China. According to the geological exploration data，the tunnel will pass through four deep weathered or slots troughs，F1，F2，F3，F4，where the strata are complete or strong weathered weak rocks. These strata have high permeability coefficients，huge water amount，high water pressure，and high risk of water and silt pouring in tunnel with infinite seawater supply. As a result，the safety of weathering slot F1 during tunnel construction is the key in the project. At present，the tunnel has been excavated to the weathered slot. In order to assure that the subsea tunnel can pass the weathered slot F1 successfully，the full-section curtain grouting technology is adopted to reinforce the weathered slot F1 to block up the water. The effect of the full-section curtain grouting in the first cycle is good；and the tunnel has been excavated for 18 m successfully. The geological condition，grouting mechanism，scheme and parameters，and the verification and appraisal of the construction techniques and grouting effect are introduced.

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GROUTING TECHNOLOGY FOR WATER BLOCKAGE OF WEATHERED SLOT F1 IN XIAMEN XIANG¢AN SUBSEA SERVICE TUNNEL

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2007, 26 (S2): -3841 doi:
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[PDF 413 KB] (910)

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Xiamen Xiang¢an subsea tunnel，with the total length of 5.948 km，is the first subsea tunnel designed and constructed by mainland China. According to the geological exploration data，the tunnel will pass through four deep weathered or slots troughs，F1，F2，F3，F4，where the strata are complete or strong weathered weak rocks. These strata have high permeability coefficients，huge water amount，high water pressure，and high risk of water and silt pouring in tunnel with infinite seawater supply. As a result，the safety of weathering slot F1 during tunnel construction is the key in the project. At present，the tunnel has been excavated to the weathered slot. In order to assure that the subsea tunnel can pass the weathered slot F1 successfully，the full-section curtain grouting technology is adopted to reinforce the weathered slot F1 to block up the water. The effect of the full-section curtain grouting in the first cycle is good；and the tunnel has been excavated for 18 m successfully. The geological condition，grouting mechanism，scheme and parameters，and the verification and appraisal of the construction techniques and grouting effect are introduced.

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STUDY ON ROCKMASS JOINT CHARACTERISTICS OF JIJI QUARRY IN BEISHAN，GANSU PROVINCE

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2007, 26 (S2): -3849 doi:
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[PDF 376 KB] (583)

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Jiji quarry is one of the candidates in Beishan area，Gansu province—the preselected area for Chinese high-level radioactive waste repository. Data of 13 012 joints of granite are mapped by comprehensive joint survey method in Jiji quarry. According to the two faults，Jiji quarry is roughly divided into three regions where the structure of rockmass is homogenous and two regions which are influenced by the two faults. Based on the theory of the circular sampling window，the computing program is developed and is used to analyze the diversity of the mean joint trace length and joint trace midpoint density in the both sides of the faults. The boundaries of the rockmass structure homogenous region are determined according to the influential range of the faults；and the mean trace length and trace midpoint density of each rockmass structure homogenous region is calculated. The optimal joint sets of each rockmass structure homogenous region are obtained by rose diagram method and equal-area upper hemisphere projection method. The probability distributions of joint dip and dip angle can be effectively fitted by normal function；and the joint dip angles are mostly steep. The joint spacing of each set of joint is calculated and can be effectively fitted by negative exponential function. According to “suggested methods for quantitative description of discontinuities in rock mass”(ISRM，1978)，the joint spacing of each rockmass structure homogenous region is wide. In this study，attention is focused on the rockmass joint characteristics，such as orientation，trace length，trace midpoint density and spacing. The quantitative parameters which can be used to describe the rockmass joint characteristics are obtained. They are essential for further research of the mechanical and seepage characteristics of rockmass.

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STUDY ON ROCKMASS JOINT CHARACTERISTICS OF JIJI QUARRY IN BEISHAN，GANSU PROVINCE

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2007, 26 (S2): -3849 doi:
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[PDF 376 KB] (784)

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Jiji quarry is one of the candidates in Beishan area，Gansu province—the preselected area for Chinese high-level radioactive waste repository. Data of 13 012 joints of granite are mapped by comprehensive joint survey method in Jiji quarry. According to the two faults，Jiji quarry is roughly divided into three regions where the structure of rockmass is homogenous and two regions which are influenced by the two faults. Based on the theory of the circular sampling window，the computing program is developed and is used to analyze the diversity of the mean joint trace length and joint trace midpoint density in the both sides of the faults. The boundaries of the rockmass structure homogenous region are determined according to the influential range of the faults；and the mean trace length and trace midpoint density of each rockmass structure homogenous region is calculated. The optimal joint sets of each rockmass structure homogenous region are obtained by rose diagram method and equal-area upper hemisphere projection method. The probability distributions of joint dip and dip angle can be effectively fitted by normal function；and the joint dip angles are mostly steep. The joint spacing of each set of joint is calculated and can be effectively fitted by negative exponential function. According to “suggested methods for quantitative description of discontinuities in rock mass”(ISRM，1978)，the joint spacing of each rockmass structure homogenous region is wide. In this study，attention is focused on the rockmass joint characteristics，such as orientation，trace length，trace midpoint density and spacing. The quantitative parameters which can be used to describe the rockmass joint characteristics are obtained. They are essential for further research of the mechanical and seepage characteristics of rockmass.

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SIMULATION ANALYSIS OF EFFECT OF STAGNANT POOL IN FRACTURE ON SOLUTE TRANSPORT

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2007, 26 (S2): -3855 doi:
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[PDF 231 KB] (656)

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The more common situations both in field and in laboratory involve nonorthogonal fractures of unequal aperture. The effect of crack shape in stagnant pool on solute tracer and the corresponding change of transport character are discussed especially. Random tracer particle method is adopted，which considers convection and diffusive steps. Numerical experiments are conducted in a homogeneous conductivity field. Simulations with different degrees of diffusion are used to compare their effect on solute transport result，i.e. character of breakthrough curves. The effects of geometric shape of fracture in stagnant pool and relative molecular diffusion degree on the solute transport are analyzed according to the characters of different breakthrough curves. Results indicate that，in the single fracture without stagnant pool，the solute pours out almost at the same time；for the same diffusion scale，the peak value of the breakthrough curves of the fractures with a deeper or wider stagnant pool decreases obviously and the tail of the curve increases. The results also demonstrate that the breakthrough curves have similar characters under the condition of higher scale of molecular diffusion.

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SIMULATION ANALYSIS OF EFFECT OF STAGNANT POOL IN FRACTURE ON SOLUTE TRANSPORT

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2007, 26 (S2): -3855 doi:
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[PDF 231 KB] (714)

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Show Abstract

The more common situations both in field and in laboratory involve nonorthogonal fractures of unequal aperture. The effect of crack shape in stagnant pool on solute tracer and the corresponding change of transport character are discussed especially. Random tracer particle method is adopted，which considers convection and diffusive steps. Numerical experiments are conducted in a homogeneous conductivity field. Simulations with different degrees of diffusion are used to compare their effect on solute transport result，i.e. character of breakthrough curves. The effects of geometric shape of fracture in stagnant pool and relative molecular diffusion degree on the solute transport are analyzed according to the characters of different breakthrough curves. Results indicate that，in the single fracture without stagnant pool，the solute pours out almost at the same time；for the same diffusion scale，the peak value of the breakthrough curves of the fractures with a deeper or wider stagnant pool decreases obviously and the tail of the curve increases. The results also demonstrate that the breakthrough curves have similar characters under the condition of higher scale of molecular diffusion.

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CHARACTERISTICS OF SWELLING PRESSURE OF DENSELY COMPACTED GAOMIAOZI BENTONITE GMZ01

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2007, 26 (S2): -3861 doi:
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[PDF 266 KB] (895)

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In the deep geological disposal of high-level radioactive waste，buffer/backfill materials act as engineering barrier，hydraulic barrier，and chemical barrier，which can transmit and propagate the heat generated by radioactive waste in the deep geological repository. Results show that bentonite is a kind of ideal buffer/backfill material. Based on a brief review of the laboratory testing techniques for the measurement of swelling pressure of expansive clay，the characteristics of swelling pressure of Gaomiaozi bentonite(GMZ01)，which has been chosen as the first choice for using as buffer/backfill materials in deep disposal of high-level radioactive waste in China，have been studied by the constant volume test method. Results show that swelling pressure changes with time nonlinearly，but there is a linear relationship between time/swelling pressure and time. Curves of swelling pressure and the amount of absorbed water varying with time can be easily classified into several typical phases. For the Gaomiaozi bentonite tested here，there is an exponential relationship between swelling pressure and dry density；and dry density is an important factor influencing swelling pressure. All results obtained here are very important for the study of expansive properties of Gaomiaozi bentonite.

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CHARACTERISTICS OF SWELLING PRESSURE OF DENSELY COMPACTED GAOMIAOZI BENTONITE GMZ01

CHARACTERISTICS OF SWELLING PRESSURE OF DENSELY COMPACTED GAOMIAOZI BENTONITE GMZ01

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2007, 26 (S2): -3861 doi:
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[PDF 355 KB] (710)

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Show Abstract

In the deep geological disposal of high-level radioactive waste，buffer/backfill materials act as engineering barrier，hydraulic barrier，and chemical barrier，which can transmit and propagate the heat generated by radioactive waste in the deep geological repository. Results show that bentonite is a kind of ideal buffer/backfill material. Based on a brief review of the laboratory testing techniques for the measurement of swelling pressure of expansive clay，the characteristics of swelling pressure of Gaomiaozi bentonite(GMZ01)，which has been chosen as the first choice for using as buffer/backfill materials in deep disposal of high-level radioactive waste in China，have been studied by the constant volume test method. Results show that swelling pressure changes with time nonlinearly，but there is a linear relationship between time/swelling pressure and time. Curves of swelling pressure and the amount of absorbed water varying with time can be easily classified into several typical phases. For the Gaomiaozi bentonite tested here，there is an exponential relationship between swelling pressure and dry density；and dry density is an important factor influencing swelling pressure. All results obtained here are very important for the study of expansive properties of Gaomiaozi bentonite.

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CHARACTERISTICS OF SWELLING PRESSURE OF DENSELY COMPACTED GAOMIAOZI BENTONITE GMZ01

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2007, 26 (S2): -3861 doi:
Full Text:

[PDF 266 KB] (884)

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Show Abstract

In the deep geological disposal of high-level radioactive waste，buffer/backfill materials act as engineering barrier，hydraulic barrier，and chemical barrier，which can transmit and propagate the heat generated by radioactive waste in the deep geological repository. Results show that bentonite is a kind of ideal buffer/backfill material. Based on a brief review of the laboratory testing techniques for the measurement of swelling pressure of expansive clay，the characteristics of swelling pressure of Gaomiaozi bentonite(GMZ01)，which has been chosen as the first choice for using as buffer/backfill materials in deep disposal of high-level radioactive waste in China，have been studied by the constant volume test method. Results show that swelling pressure changes with time nonlinearly，but there is a linear relationship between time/swelling pressure and time. Curves of swelling pressure and the amount of absorbed water varying with time can be easily classified into several typical phases. For the Gaomiaozi bentonite tested here，there is an exponential relationship between swelling pressure and dry density；and dry density is an important factor influencing swelling pressure. All results obtained here are very important for the study of expansive properties of Gaomiaozi bentonite.

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APPLICATION OF INTEGRATED BOREHOLE MEASUREMENT TECHNIQUES TO HYDROGEOLOGICAL CHARACTERISTICS EVALUATION OF WATER-CONDUCTIVE FAULT

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2007, 26 (S2): -3866 doi:
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[PDF 634 KB] (896)

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The hydrogeological characteristic of water-conductive fault is a critical part of site selection and evaluation of high-level radioactive waste geological disposal system. Borehole radar measurement provides the useful information of geological features of extension in the rock mass. Acoustic borehole televiewer measurement provides the borehole-wall images in the degree of 360. The lithologic character，orientation and structural planes，and the relation between structural planes can be defined for studies of fault on the basis of borehole-wall images. Multi-parameter hydrochemical logging is a useful technique for identifying the vertical distribution of hydrochemical parameters in the deep environment. Injection test with double-packer can measure permeability coefficient of hydraulically conductive intervals intersecting boreholes. Data obtained from a single technique cannot provide a definitive and full estimation of hydrogeological properties of water-conductive fault. Integrated borehole measurement technique is the combined application of several techniques with integrated interpretation which not only exerts synergistic effect of borehole measurements but also improves the credibility of data in comparison of the results obtained by single measurement. An example is presented to perform the combined application of these techniques to characterize the hydraulic properties of water-conductive fault intersected by BS03 in the potential site，Beishan preselected area，Gansu Province for high-level radioactive waste geological disposal. Hydrogeological model of water-conductive fault is established.

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APPLICATION OF INTEGRATED BOREHOLE MEASUREMENT TECHNIQUES TO HYDROGEOLOGICAL CHARACTERISTICS EVALUATION OF WATER-CONDUCTIVE FAULT

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2007, 26 (S2): -3866 doi:
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[PDF 634 KB] (662)

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Show Abstract

The hydrogeological characteristic of water-conductive fault is a critical part of site selection and evaluation of high-level radioactive waste geological disposal system. Borehole radar measurement provides the useful information of geological features of extension in the rock mass. Acoustic borehole televiewer measurement provides the borehole-wall images in the degree of 360. The lithologic character，orientation and structural planes，and the relation between structural planes can be defined for studies of fault on the basis of borehole-wall images. Multi-parameter hydrochemical logging is a useful technique for identifying the vertical distribution of hydrochemical parameters in the deep environment. Injection test with double-packer can measure permeability coefficient of hydraulically conductive intervals intersecting boreholes. Data obtained from a single technique cannot provide a definitive and full estimation of hydrogeological properties of water-conductive fault. Integrated borehole measurement technique is the combined application of several techniques with integrated interpretation which not only exerts synergistic effect of borehole measurements but also improves the credibility of data in comparison of the results obtained by single measurement. An example is presented to perform the combined application of these techniques to characterize the hydraulic properties of water-conductive fault intersected by BS03 in the potential site，Beishan preselected area，Gansu Province for high-level radioactive waste geological disposal. Hydrogeological model of water-conductive fault is established.

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COUPLED THERMO-GAS-MECHANICAL SIMULATION FOR YUCCA MOUNTAIN DRIFT SCALE TEST BY DISCRETE ELEMENT METHOD

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2007, 26 (S2): -3874 doi:
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[PDF 631 KB] (719)

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The basic theoretical background，control equations and computation principle for solving thermo-hydro-mechanical(T-H-M) coupling problem in UDEC(Version 4.0) of 2D discrete element method are presented. Against the coupled T-H-M processes(here “H”is non-wetting fluid) in near field of drift scale test for geological disposal of high-level radioactive nuclear waste at Yucca Mountain，Nevada，USA，a numerical simulation is carried out by using UDEC. The changes of displacements，principal stresses，joint apertures，non-wetting fluid pressures and flow rates are analyzed. Some calculation results are compared with in-situ measured data and other results obtained by finite element and/or finite difference methods. The following results can be obtained. (1) The distributions and changes of temperatures and stresses are close to each other for the three results. (2) The displacement distributions obtained by UDEC approach qualitatively those of LBNL analysis；and both of them have obvious quantitative differences when heating time is shorter，but the differences are within the same magnitude order. (3) When the heating time is longer，the approaching extents of the measured data of the displacements by UDEC and those by LBNL analysis are match on the whole. So it can be considered that the simulation of coupled T-H-M processes in geological disposal of nuclear waste by discrete element method is practicable.

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COUPLED THERMO-GAS-MECHANICAL SIMULATION FOR YUCCA MOUNTAIN DRIFT SCALE TEST BY DISCRETE ELEMENT METHOD

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2007, 26 (S2): -3874 doi:
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[PDF 631 KB] (726)

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Show Abstract

The basic theoretical background，control equations and computation principle for solving thermo-hydro-mechanical(T-H-M) coupling problem in UDEC(Version 4.0) of 2D discrete element method are presented. Against the coupled T-H-M processes(here “H”is non-wetting fluid) in near field of drift scale test for geological disposal of high-level radioactive nuclear waste at Yucca Mountain，Nevada，USA，a numerical simulation is carried out by using UDEC. The changes of displacements，principal stresses，joint apertures，non-wetting fluid pressures and flow rates are analyzed. Some calculation results are compared with in-situ measured data and other results obtained by finite element and/or finite difference methods. The following results can be obtained. (1) The distributions and changes of temperatures and stresses are close to each other for the three results. (2) The displacement distributions obtained by UDEC approach qualitatively those of LBNL analysis；and both of them have obvious quantitative differences when heating time is shorter，but the differences are within the same magnitude order. (3) When the heating time is longer，the approaching extents of the measured data of the displacements by UDEC and those by LBNL analysis are match on the whole. So it can be considered that the simulation of coupled T-H-M processes in geological disposal of nuclear waste by discrete element method is practicable.

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AN OVERVIEW OF TEST TECHNIQUE AND THEORY STUDY OF SLUG TEST

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2007, 26 (S2): -3882 doi:
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[PDF 370 KB] (790)

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Slug test is an important hydraulic test technique to evaluate the local hydraulic properties of formation. Slug test has become such a frequently used technique as a result of its considerable logistical and economic advantages such as relatively low cost，simplicity，short duration of test，no water actually removed from or added to the well. There are more than fifty years of development history of this test in foreign countries；and its development is summarized as technique development and theoretical model development. Slug test technique can be divided into simple slug test，packer slug test and shut-in slug test. The theoretical models for slug test include exponential decay model，underdamped model and nonlinear model. The parameters obtained from slug test have been widely used in a variety of aspects，such as contamination hydrogeology，water supply investigations，near-surface agricultural hydrogeology，petroleum and coalbed-methane. The influential range of slug test is very small；and it is only possible to determine the characteristics of small volume of aquifer material surrounding the well due to intrinsic limitation of this technique. Recently，slug test is considered as an important technique to evaluate the spatial variations of aquifer seepage parameters and seepage characteristics of rock mass with low，even extremely low permeability. Shut-in slug test technique is utilized to in-situ measurement of rock mass permeability with permeability coefficient lower that 10－13 m/s.

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AN OVERVIEW OF TEST TECHNIQUE AND THEORY STUDY OF SLUG TEST

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2007, 26 (S2): -3882 doi:
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[PDF 370 KB] (768)

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Slug test is an important hydraulic test technique to evaluate the local hydraulic properties of formation. Slug test has become such a frequently used technique as a result of its considerable logistical and economic advantages such as relatively low cost，simplicity，short duration of test，no water actually removed from or added to the well. There are more than fifty years of development history of this test in foreign countries；and its development is summarized as technique development and theoretical model development. Slug test technique can be divided into simple slug test，packer slug test and shut-in slug test. The theoretical models for slug test include exponential decay model，underdamped model and nonlinear model. The parameters obtained from slug test have been widely used in a variety of aspects，such as contamination hydrogeology，water supply investigations，near-surface agricultural hydrogeology，petroleum and coalbed-methane. The influential range of slug test is very small；and it is only possible to determine the characteristics of small volume of aquifer material surrounding the well due to intrinsic limitation of this technique. Recently，slug test is considered as an important technique to evaluate the spatial variations of aquifer seepage parameters and seepage characteristics of rock mass with low，even extremely low permeability. Shut-in slug test technique is utilized to in-situ measurement of rock mass permeability with permeability coefficient lower that 10－13 m/s.

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THERMAL PROPERTIES OF BUFFER MATERIAL FOR HIGH-LEVEL RADIOACTIVE WASTE DISPOSAL

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2007, 26 (S2): -3891 doi:
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[PDF 298 KB] (714)

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Buffer material is one of the important engineered barriers in the high-level radioactive waste(HLW) repository. Its thermal property is one of the key properties for the design of HLW repository. ISOMET apparatus is used to measure the thermal properties of compacted mixture samples GMZM composed of Gaomiaozi Na-bentonite GMZ01，silica sand and graphite under different dry densities and different water contents. The experimental results show that thermal conductivity，thermal capacity and thermal diffusivity of GMZM increase as the dry density and water content increase. Compared with the thermal properties of GMZ01，additive of silica sand and graphite significantly increase the thermal conductivity and thermal diffusivity of compacted buffer material as the density increases. But there is no significant influence on specific thermal capacity. When the dry density is greater than 1.8 g/cm3，the thermal conductivity and thermal diffusivity of GMZM increase 20% than those of GMZ01. Thermal property of buffer material is related to water content，dry density，mineral composition and microstructure etc.. Thermal conductivity increases with the water content and dry density increase. But there is no uniform linear relationship between thermal conductivity and water content，dry density respectively. When the saturation is more than 20%，linear relationships between saturation and the thermal conductivity，thermal capacity，thermal diffusivity of compacted GMZ01 are observed respectively.

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THERMAL PROPERTIES OF BUFFER MATERIAL FOR HIGH-LEVEL RADIOACTIVE WASTE DISPOSAL

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2007, 26 (S2): -3891 doi:
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[PDF 298 KB] (1076)

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Buffer material is one of the important engineered barriers in the high-level radioactive waste(HLW) repository. Its thermal property is one of the key properties for the design of HLW repository. ISOMET apparatus is used to measure the thermal properties of compacted mixture samples GMZM composed of Gaomiaozi Na-bentonite GMZ01，silica sand and graphite under different dry densities and different water contents. The experimental results show that thermal conductivity，thermal capacity and thermal diffusivity of GMZM increase as the dry density and water content increase. Compared with the thermal properties of GMZ01，additive of silica sand and graphite significantly increase the thermal conductivity and thermal diffusivity of compacted buffer material as the density increases. But there is no significant influence on specific thermal capacity. When the dry density is greater than 1.8 g/cm3，the thermal conductivity and thermal diffusivity of GMZM increase 20% than those of GMZ01. Thermal property of buffer material is related to water content，dry density，mineral composition and microstructure etc.. Thermal conductivity increases with the water content and dry density increase. But there is no uniform linear relationship between thermal conductivity and water content，dry density respectively. When the saturation is more than 20%，linear relationships between saturation and the thermal conductivity，thermal capacity，thermal diffusivity of compacted GMZ01 are observed respectively.

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ANALYSIS OF SURROUNDING ROCK STABILITY OF MUDSTONE LARGE-DEFORMATION TUNNEL EXCAVATED BY SHIELD CONSTRUCTION METHOD

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2007, 26 (S2): -3897 doi:
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[PDF 1772 KB] (723)

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Taking the high-level radioactive waste repository in Belgium as background，based on the comprehensive analysis of the main factors influencing the stability of surrounding rock during tunnel excavation，an elastoplastic seepage flow-stress coupling analysis model is set up according to the effective stress analysis method；and a 3D nonlinear finite element method is put forward to simulate the excavation of tunnel by shield machine. The distributions of pore pressure，stress field，displacement field of surrounding rock and the lining stress of concrete segment are analyzed in detail. The results can provide references to construction and field measurement of mudstone shield tunnel.

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ANALYSIS OF SURROUNDING ROCK STABILITY OF MUDSTONE LARGE-DEFORMATION TUNNEL EXCAVATED BY SHIELD CONSTRUCTION METHOD

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2007, 26 (S2): -3897 doi:
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[PDF 1772 KB] (748)

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Taking the high-level radioactive waste repository in Belgium as background，based on the comprehensive analysis of the main factors influencing the stability of surrounding rock during tunnel excavation，an elastoplastic seepage flow-stress coupling analysis model is set up according to the effective stress analysis method；and a 3D nonlinear finite element method is put forward to simulate the excavation of tunnel by shield machine. The distributions of pore pressure，stress field，displacement field of surrounding rock and the lining stress of concrete segment are analyzed in detail. The results can provide references to construction and field measurement of mudstone shield tunnel.

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DESIGN OF HIGH-LEVEL RADIOACTIVE WASTE REPOSITORY

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2007, 26 (S2): -3904 doi:
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[PDF 256 KB] (725)

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A high-level radioactive waste repository is a kind of special underground rock engineering with many characteristics and special design methodology. The characteristics of repository as an underground engineering are summarized；and the major contents，design processes and factors to be taken into account are briefly introduced by taking the design of Swedish repository in stage D1 as an example. Finally some design-related issues are discussed，such as the function and lifetime of the repository，conceptive design，general requirements，temperature limitation，main issues for repositories in different host rocks，design requirements for retrieval and the cost of repository.

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DESIGN OF HIGH-LEVEL RADIOACTIVE WASTE REPOSITORY

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2007, 26 (S2): -3904 doi:
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[PDF 256 KB] (837)

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A high-level radioactive waste repository is a kind of special underground rock engineering with many characteristics and special design methodology. The characteristics of repository as an underground engineering are summarized；and the major contents，design processes and factors to be taken into account are briefly introduced by taking the design of Swedish repository in stage D1 as an example. Finally some design-related issues are discussed，such as the function and lifetime of the repository，conceptive design，general requirements，temperature limitation，main issues for repositories in different host rocks，design requirements for retrieval and the cost of repository.

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COUPLING ANALYSIS OF SEEPAGE AND STRESS-STRAIN OF ROCK FRACTURE DURING SHEAR PROCESS

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2007, 26 (S2): -3912 doi:
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[PDF 411 KB] (551)

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Considering the different levels of normal stress，the relationship between shear stress and shear deformation of rock fracture is built firstly. The elastic matrix for rock fracture is improved；and the relationship between the shear deformation and the shear stress is divided into three phases，i.e. shear shrink，shear dilation up to peak value，residual shear strength. Then，applying the composite element algorithm，the coupling mechanism of seepage and stress-strain for rock fracture during shear process is realized，by which the variation and relationship among shear deformation，aperture of rock fracture，conductivity of rock fracture，seepage field as well as stress filed are illustrated. The numerical example indicates that，with constant mechanical parameters of filling medium in the fracture，the flow velocity of fracture keeps constant as well and does not change with variable shear deformation and normal stress，but the discharge per unit width through rock fracture changes because of the change of fracture aperture；while with lower normal stress，the shear deformation has more influences on the fracture aperture and the discharge per unit width through rock fracture.

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COUPLING ANALYSIS OF SEEPAGE AND STRESS-STRAIN OF ROCK FRACTURE DURING SHEAR PROCESS

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2007, 26 (S2): -3912 doi:
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[PDF 411 KB] (827)

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Considering the different levels of normal stress，the relationship between shear stress and shear deformation of rock fracture is built firstly. The elastic matrix for rock fracture is improved；and the relationship between the shear deformation and the shear stress is divided into three phases，i.e. shear shrink，shear dilation up to peak value，residual shear strength. Then，applying the composite element algorithm，the coupling mechanism of seepage and stress-strain for rock fracture during shear process is realized，by which the variation and relationship among shear deformation，aperture of rock fracture，conductivity of rock fracture，seepage field as well as stress filed are illustrated. The numerical example indicates that，with constant mechanical parameters of filling medium in the fracture，the flow velocity of fracture keeps constant as well and does not change with variable shear deformation and normal stress，but the discharge per unit width through rock fracture changes because of the change of fracture aperture；while with lower normal stress，the shear deformation has more influences on the fracture aperture and the discharge per unit width through rock fracture.

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CALCULATION OF SATURATED PERMEABILITY COEFFICIENT OF BENTONITE

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2007, 26 (S2): -3920 doi:
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[PDF 0 KB] (651)

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It is very important to analyze the effect of leachate on permeability properties of geosynthetic clay liner(GCL) when GCL is used as the liner of landfill. To overcome the shortcomings in seepage test such as weak repeatability and time-consumption，the saturated permeability coefficient of GCL is studied in a microscopic angle. Firstly，change law of intraparticle void ratio with CaCl2 concentration is found based on the current knowledge about microstructure of bentonite and the results from SEM method. Secondly，taking bentonite as dual porous media，calculation formula of the distance between layers of gel-type montmorillonite in interparticle pores，，is deduced. Finally，improved calculation method of permeability coefficient is derived using and Poiseuille law. The method can take the effect of the changes of CaCl2 concentration and void ratio on permeability coefficient into account. And the comparison of calculated and measured permeability coefficient validates the method. It is shown that the changes of is resulted from the changes of both apparent porosity and the distance between layers of gel-type montmorillonite in interparticle pores.

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CALCULATION OF SATURATED PERMEABILITY COEFFICIENT OF BENTONITE

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2007, 26 (S2): -3920 doi:
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[PDF 200 KB] (1841)

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It is very important to analyze the effect of leachate on permeability properties of geosynthetic clay liner(GCL) when GCL is used as the liner of landfill. To overcome the shortcomings in seepage test such as weak repeatability and time-consumption，the saturated permeability coefficient of GCL is studied in a microscopic angle. Firstly，change law of intraparticle void ratio with CaCl2 concentration is found based on the current knowledge about microstructure of bentonite and the results from SEM method. Secondly，taking bentonite as dual porous media，calculation formula of the distance between layers of gel-type montmorillonite in interparticle pores，，is deduced. Finally，improved calculation method of permeability coefficient is derived using and Poiseuille law. The method can take the effect of the changes of CaCl2 concentration and void ratio on permeability coefficient into account. And the comparison of calculated and measured permeability coefficient validates the method. It is shown that the changes of is resulted from the changes of both apparent porosity and the distance between layers of gel-type montmorillonite in interparticle pores.

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KEY SCIENTIFIC ISSUES OF GEOLOGY，HYDROGEOLOGY AND GEOCHEMISTRY IN HIGH-LEVEL RADIOACTIVE WASTE GEOLOGICAL DISPOSAL

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2007, 26 (S2): -3926 doi:
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[PDF 208 KB] (997)

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The deep geological disposal scheme is widely accepted for high-level radioactive waste disposal in the world. The conceptual design of “multi-barrier system”，man-made and natural barriers，is adopted for disposal repository in the scheme. The natural barrier is a very important safe guarantee for repository operation in long term. The selection of reliable natural barrier depends mainly on the work related to geology，hydrogeology and geochemistry. Through the review of high-level radioactive waste disposal research in home and abroad，the key scientific issues related to geology，hydrogeology and geochemistry in the high-level radioactive waste disposal research are explained in detail；and the mainly content，method and means used in the investigation for disposal site are introduced. The hydrogeological，geochemical issues regarded in the world at present，such as hydrogeological and hydrogeochemical modelling，migration of radionuclide in the natural medium，the interaction among groundwater-waste-rock，the geochemical closeness of rock mass and so on，are also discussed.

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KEY SCIENTIFIC ISSUES OF GEOLOGY，HYDROGEOLOGY AND GEOCHEMISTRY IN HIGH-LEVEL RADIOACTIVE WASTE GEOLOGICAL DISPOSAL

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2007, 26 (S2): -3926 doi:
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[PDF 208 KB] (766)

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Show Abstract

The deep geological disposal scheme is widely accepted for high-level radioactive waste disposal in the world. The conceptual design of “multi-barrier system”，man-made and natural barriers，is adopted for disposal repository in the scheme. The natural barrier is a very important safe guarantee for repository operation in long term. The selection of reliable natural barrier depends mainly on the work related to geology，hydrogeology and geochemistry. Through the review of high-level radioactive waste disposal research in home and abroad，the key scientific issues related to geology，hydrogeology and geochemistry in the high-level radioactive waste disposal research are explained in detail；and the mainly content，method and means used in the investigation for disposal site are introduced. The hydrogeological，geochemical issues regarded in the world at present，such as hydrogeological and hydrogeochemical modelling，migration of radionuclide in the natural medium，the interaction among groundwater-waste-rock，the geochemical closeness of rock mass and so on，are also discussed.

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ROCK FAILURE ISSUES IN GEOLOGICAL DISPOSAL OF HIGH-LEVEL RADIOACTIVE WASTES UNDER MULTI-FIELD COUPLING FUNCTION

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2007, 26 (S2): -3932 doi:
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[PDF 764 KB] (852)

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The research progress in thermal-hydraulic-mechanical(THM) coupling model in rock mechanics is summarized. The rock(rock mass) failure process under the thermal-hydraulic-mechanical coupling function will directly affect the thermodynamic characteristic，the seepage characteristic and mechanical stability of surrounding rock around high-level radioactive wastes geological disposal repository，further affect the migration rules of high-level radioactive nuclide in surrounding rock. The macroscopical behavior of rock structure failure is modeled by building a model which describes the rock(rock mass) failure process under the thermal-hydraulic-
mechanical coupling function. The analysis results show that this method has important scientific values and practical significances for the reliability of high-level radioactive wastes disposal.

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ROCK FAILURE ISSUES IN GEOLOGICAL DISPOSAL OF HIGH-LEVEL RADIOACTIVE WASTES UNDER MULTI-FIELD COUPLING FUNCTION

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2007, 26 (S2): -3932 doi:
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[PDF 764 KB] (1017)

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The research progress in thermal-hydraulic-mechanical(THM) coupling model in rock mechanics is summarized. The rock(rock mass) failure process under the thermal-hydraulic-mechanical coupling function will directly affect the thermodynamic characteristic，the seepage characteristic and mechanical stability of surrounding rock around high-level radioactive wastes geological disposal repository，further affect the migration rules of high-level radioactive nuclide in surrounding rock. The macroscopical behavior of rock structure failure is modeled by building a model which describes the rock(rock mass) failure process under the thermal-hydraulic-
mechanical coupling function. The analysis results show that this method has important scientific values and practical significances for the reliability of high-level radioactive wastes disposal.

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THM COUPLING THEORY AND ANALYSES OF HIGH-LEVEL RADIOACTIVE WASTE DISPOSAL

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2007, 26 (S2): -3939 doi:
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[PDF 420 KB] (691)

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The research of high-level radioactive waste disposal is very necessary and important；and the determination of high-level radioactive waste disposal scheme is of importance for high-level radioactive waste repository safety. The high-level radioactive waste disposal structure is based on the physico-mechanical properties of rock mass and expansive soil. Based on the high-level radioactive waste disposal types，the relative research projects are proposed；and the THM coupling theories are introduced. The soil-water characteristics curve of bentonite depends on not only external loaded force，vapor pressure and hydraulic pressure，but also on the temperature in the high-level radioactive waste disposal. The conservation equation of water quantity in the gas and liquid states is established by considering the propagation of gas under pressure gradient，the solution of gas in the water，the condensation of gas in the water，etc.. The energy conservation equation is obtained by considering the influences of sensitive thermal flow and potential thermal flow. The schemes of finite element and finite difference are deduced. Finally，the one-dimensional code and calculation are performed. The numerical result is valuable for the determination of chamber distance of high-level radioactive waste disposal shaft.

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THM COUPLING THEORY AND ANALYSES OF HIGH-LEVEL RADIOACTIVE WASTE DISPOSAL

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2007, 26 (S2): -3939 doi:
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[PDF 420 KB] (633)

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The research of high-level radioactive waste disposal is very necessary and important；and the determination of high-level radioactive waste disposal scheme is of importance for high-level radioactive waste repository safety. The high-level radioactive waste disposal structure is based on the physico-mechanical properties of rock mass and expansive soil. Based on the high-level radioactive waste disposal types，the relative research projects are proposed；and the THM coupling theories are introduced. The soil-water characteristics curve of bentonite depends on not only external loaded force，vapor pressure and hydraulic pressure，but also on the temperature in the high-level radioactive waste disposal. The conservation equation of water quantity in the gas and liquid states is established by considering the propagation of gas under pressure gradient，the solution of gas in the water，the condensation of gas in the water，etc.. The energy conservation equation is obtained by considering the influences of sensitive thermal flow and potential thermal flow. The schemes of finite element and finite difference are deduced. Finally，the one-dimensional code and calculation are performed. The numerical result is valuable for the determination of chamber distance of high-level radioactive waste disposal shaft.

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NUMERICAL SIMULATION OF GUIDED WAVE PROPAGATION IN ANCHORED BOLTS

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2007, 26 (S2): -3946 doi:
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[PDF 392 KB] (566)

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Based on the anchorage mechanism of bolts，a model for the anchorage system is established. An embedded bolt can be regarded as a waveguide according to the propagation properties of guided waves. The frequency equations of axisymmetrical longitudinal guided waves for the embedded bolts are deduced；and the dispersion curves are plotted. According to the optimal simulation results of guided waves at high and low frequencies，the reflection from the upper interface of anchorage segment can be detected at a frequency of 75 kHz；and the effective bonding length of the embedded bolts can be further figured out according to the reflection time and wave velocity. The end reflection of the bolt can be identified at 2 MHz；and the attenuation coefficient for bolts can be obtained according to the relationship between incident and reflected waves amplititudes，by which the archorage quality of the embedded bolts can be evaluated.

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NUMERICAL SIMULATION OF GUIDED WAVE PROPAGATION IN ANCHORED BOLTS

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2007, 26 (S2): -3946 doi:
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[PDF 392 KB] (764)

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Show Abstract

Based on the anchorage mechanism of bolts，a model for the anchorage system is established. An embedded bolt can be regarded as a waveguide according to the propagation properties of guided waves. The frequency equations of axisymmetrical longitudinal guided waves for the embedded bolts are deduced；and the dispersion curves are plotted. According to the optimal simulation results of guided waves at high and low frequencies，the reflection from the upper interface of anchorage segment can be detected at a frequency of 75 kHz；and the effective bonding length of the embedded bolts can be further figured out according to the reflection time and wave velocity. The end reflection of the bolt can be identified at 2 MHz；and the attenuation coefficient for bolts can be obtained according to the relationship between incident and reflected waves amplititudes，by which the archorage quality of the embedded bolts can be evaluated.

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EXPERIMENTAL STUDY ON CYCLE PROPERTY OF GROUNDWATER IN FRACTURED GRANITE IN BEISHAN，CHINA

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2007, 26 (S2): -3954 doi:
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[PDF 488 KB] (735)

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The pilot site for high-level radioactive waste repository in China is located in Beishan granite body of Gansu Province. Test borehole No.3(BS03) is seated in the area belonging to ground run-off zone of the regional groundwater system. The borehole is drilled specially for site evaluation. A group of depth-specific groundwater samples have been obtained for the first time from three different depth levels，i.e. 144.00–156.77，208.00–238.00，430.51–445.72 m in the borehole using a double-packer down-hole sampling and testing system. Stable isotopes d2H and d18O of the groundwater samples indicate that the recharge of the groundwater mainly comes from local precipitation. It is different from the earlier oppinion that the recharge of the groundwater comes from Qilian Mountains. 3H and CFCs contents show that the age of the groundwater at the interested depths is at least 60 years.

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EXPERIMENTAL STUDY ON CYCLE PROPERTY OF GROUNDWATER IN FRACTURED GRANITE IN BEISHAN，CHINA

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2007, 26 (S2): -3954 doi:
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[PDF 488 KB] (832)

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Show Abstract

The pilot site for high-level radioactive waste repository in China is located in Beishan granite body of Gansu Province. Test borehole No.3(BS03) is seated in the area belonging to ground run-off zone of the regional groundwater system. The borehole is drilled specially for site evaluation. A group of depth-specific groundwater samples have been obtained for the first time from three different depth levels，i.e. 144.00–156.77，208.00–238.00，430.51–445.72 m in the borehole using a double-packer down-hole sampling and testing system. Stable isotopes d2H and d18O of the groundwater samples indicate that the recharge of the groundwater mainly comes from local precipitation. It is different from the earlier oppinion that the recharge of the groundwater comes from Qilian Mountains. 3H and CFCs contents show that the age of the groundwater at the interested depths is at least 60 years.

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RANDOM FIELD MODEL AND RELIABILITY ANALYSIS OF FOUNDATION SOIL IN TIANJIN PORT

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2007, 26 (S2): -3959 doi:
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[PDF 314 KB] (709)

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The theory of random field plays an important role in reliability analysis of foundations. The key to application of random field theory to reliability analysis is how to combine the reduction function of variance obtained by the random theory with the reliability theory. Based on a large amount of investigation data in Tianjin Port，a random field model is established for the soil profiles in this area. The correlation function，correlation distance and irrelated distance are studied and the representative values of them of local area are provided. In addition，how to correctly choose the reduction function of variance and to reasonably apply it to the reliability analysis is discussed. The principle for determination of reduction function of variance is presented and applied to the probabilistic slope stability analysis. It is proven that the reliability indexes obtained by reducing the variance of shear strength indexes according to this principle agree well with the reliability of practical engineering. The developed method may give guidance to introduce the theory of random field into reliability analysis of soil foundations. Finally，the sensitivity analysis of parameters c and j in reliability calculation of slope stability is carried out. It is concluded that the effect of parameter j is larger than that of parameter c.

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RANDOM FIELD MODEL AND RELIABILITY ANALYSIS OF FOUNDATION SOIL IN TIANJIN PORT

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2007, 26 (S2): -3959 doi:
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[PDF 314 KB] (699)

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Show Abstract

The theory of random field plays an important role in reliability analysis of foundations. The key to application of random field theory to reliability analysis is how to combine the reduction function of variance obtained by the random theory with the reliability theory. Based on a large amount of investigation data in Tianjin Port，a random field model is established for the soil profiles in this area. The correlation function，correlation distance and irrelated distance are studied and the representative values of them of local area are provided. In addition，how to correctly choose the reduction function of variance and to reasonably apply it to the reliability analysis is discussed. The principle for determination of reduction function of variance is presented and applied to the probabilistic slope stability analysis. It is proven that the reliability indexes obtained by reducing the variance of shear strength indexes according to this principle agree well with the reliability of practical engineering. The developed method may give guidance to introduce the theory of random field into reliability analysis of soil foundations. Finally，the sensitivity analysis of parameters c and j in reliability calculation of slope stability is carried out. It is concluded that the effect of parameter j is larger than that of parameter c.

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PRELIMINARY DISCUSSION ON DEPTH FOR HIGH-LEVEL RADIOACTIVE WASTE REPOSITORY IN JIUJING BLOCK，BEISHAN AREA，GANSU PROVINCE

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2007, 26 (S2): -3966 doi:
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[PDF 301 KB] (687)

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It is very important to confirm the depth and area for high-level radioactive waste(HLW) repository，especially in the HLW concept model and engineering design. The general requirements for determining the depth of the HLW disposal repository are discussed. The geological characteristic，hydrogeological characteristic，rock mechanics characteristic and geostresses characteristic are analyzed in Jiujing block，Beishan area，Gansu Province. Simultaneously，the initial geostresses and the geostresses after excavation are analyzed，and the probability of tunnel stability and rockburst are also calculated and predicted. The conclusion shows that the rock mass is intact；the underground water is short of supply and has a reduce environment 400 m below ground surface；the rock has a high uniaxial strength and the rock mass has good quality. The geostress is a general geostress field range from zero to 700 m below ground surface；and the tunnel stability and rockburst analysis display that the rockburst can not happen in the area from 400 m to 700 m below ground surface. According to the general requirements for the depth of repository，the designed depth of HLW disposal repository should be located in 400–700 m below ground surface.

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PRELIMINARY DISCUSSION ON DEPTH FOR HIGH-LEVEL RADIOACTIVE WASTE REPOSITORY IN JIUJING BLOCK，BEISHAN AREA，GANSU PROVINCE

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2007, 26 (S2): -3966 doi:
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[PDF 301 KB] (543)

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Show Abstract

It is very important to confirm the depth and area for high-level radioactive waste(HLW) repository，especially in the HLW concept model and engineering design. The general requirements for determining the depth of the HLW disposal repository are discussed. The geological characteristic，hydrogeological characteristic，rock mechanics characteristic and geostresses characteristic are analyzed in Jiujing block，Beishan area，Gansu Province. Simultaneously，the initial geostresses and the geostresses after excavation are analyzed，and the probability of tunnel stability and rockburst are also calculated and predicted. The conclusion shows that the rock mass is intact；the underground water is short of supply and has a reduce environment 400 m below ground surface；the rock has a high uniaxial strength and the rock mass has good quality. The geostress is a general geostress field range from zero to 700 m below ground surface；and the tunnel stability and rockburst analysis display that the rockburst can not happen in the area from 400 m to 700 m below ground surface. According to the general requirements for the depth of repository，the designed depth of HLW disposal repository should be located in 400–700 m below ground surface.

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STUDY ON GRANITE CHARACTERISTICS OF XINCHANG SECTION OF CANDIDATE BEISHAN AREA，GANSU PROVINCE

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2007, 26 (S2): -3974 doi:
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[PDF 228 KB] (970)

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Xinchang section is one of the candidate fields in Beishan area，Gansu Province—the preselected area for China¢s high-level radioactive waste repository. The results show that the dominant rock characteriastics from Xinchang section are monolithic granite and granodiorite. The minor dominant rock is the quartz diorite. Mineral assemblage such as hornblende，magnetite，sphene，titanite，etc. show that the kinds of minerals mentioned above are of syntectic or I-typed granite. Some mineral assemblages of granodiorites such as muscovite，garnet，etc. are found during upper crust forming. The petrochemistry composition belongs to high potassium Ca-alkaline series，showing the special feature of syntectic or I-typed granite.

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STUDY ON GRANITE CHARACTERISTICS OF XINCHANG SECTION OF CANDIDATE BEISHAN AREA，GANSU PROVINCE

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2007, 26 (S2): -3974 doi:
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[PDF 228 KB] (841)

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Xinchang section is one of the candidate fields in Beishan area，Gansu Province—the preselected area for China¢s high-level radioactive waste repository. The results show that the dominant rock characteriastics from Xinchang section are monolithic granite and granodiorite. The minor dominant rock is the quartz diorite. Mineral assemblage such as hornblende，magnetite，sphene，titanite，etc. show that the kinds of minerals mentioned above are of syntectic or I-typed granite. Some mineral assemblages of granodiorites such as muscovite，garnet，etc. are found during upper crust forming. The petrochemistry composition belongs to high potassium Ca-alkaline series，showing the special feature of syntectic or I-typed granite.

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MODELING STUDY ON SPECIATION OF NUCLIDE ELEMENTS IN UNDERGROUND WATER FROM GRANITE FRACTURES

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2007, 26 (S2): -3982 doi:
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[PDF 332 KB] (599)

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The knowledge of speciation is the key contents of performing safety assessment studies for high-level radioactive waste repositories. As the main elements of high-level radioactive waste，three radionuclides，Np(IV)，Pu(IV)，Am(III)，are calculated by using EQ3NR of geochemical model EQ3/6. The main speciation of the three radionuclides，Np(IV)，Pu(IV)，Am(III)，are NpO2＋，Pu(OH)5－，AmCO3＋，Am3＋，Am(OH)2＋in the underground water. This paper also studies the speciation of the three nuclide elements，i.e. Np(IV)，Pu(IV)，Am(III)，under different conditions such as various pH values，the concentrations of Cl－，F－，SO42－and HCO3－. The study illustrates that increase or decrease of pH values will affect the variety of the speciations of Np(IV)，Pu(IV)，Am(III)，and the concentrations of Cl－，F－，SO42－and HCO3－have the less impact on the speciations of Np(IV)，Pu(IV)，Am(III).

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MODELING STUDY ON SPECIATION OF NUCLIDE ELEMENTS IN UNDERGROUND WATER FROM GRANITE FRACTURES

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2007, 26 (S2): -3982 doi:
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[PDF 332 KB] (746)

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The knowledge of speciation is the key contents of performing safety assessment studies for high-level radioactive waste repositories. As the main elements of high-level radioactive waste，three radionuclides，Np(IV)，Pu(IV)，Am(III)，are calculated by using EQ3NR of geochemical model EQ3/6. The main speciation of the three radionuclides，Np(IV)，Pu(IV)，Am(III)，are NpO2＋，Pu(OH)5－，AmCO3＋，Am3＋，Am(OH)2＋in the underground water. This paper also studies the speciation of the three nuclide elements，i.e. Np(IV)，Pu(IV)，Am(III)，under different conditions such as various pH values，the concentrations of Cl－，F－，SO42－and HCO3－. The study illustrates that increase or decrease of pH values will affect the variety of the speciations of Np(IV)，Pu(IV)，Am(III)，and the concentrations of Cl－，F－，SO42－and HCO3－have the less impact on the speciations of Np(IV)，Pu(IV)，Am(III).

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3D GEOLOGICAL MODELLING IN JIUJING BLOCK，BEISHAN AREA，GANSU PROVINCE AND APPLICATION OF ROCKFLOW TO NUCLIDES MIGRATION SIMULATION

3D GEOLOGICAL MODELLING IN JIUJING BLOCK，BEISHAN AREA，GANSU PROVINCE AND APPLICATION OF ROCKFLOW TO NUCLIDES MIGRATION SIMULATION

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2007, 26 (S2): -3989 doi:
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[PDF 420 KB] (685)

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Through analyzing the geological structure，hydrogeology，geophysics and borehole data in Jiujing block，a simple 3D geological model was constructed by using the correspondence software for Jiujing block，Beishan area，Gansu Province. On the basis of the 3D faults stable fluid field，the 2D matrix diffusion and sorption，the nuclides decay were calculated and simulated by using RockFlow. Simultaneously，the underground fluid and nuclides migration in the matrix and fault were simulated，and the temporal and spatial distributions of underground fluid and nuclides were also studied. The result shows that the 3D geological model is a very useful site assessment method，from which the spatial distribution of the host rock and faults can be displayed directly. Secondly，the key migration channel of nuclides is fracture；and the nuclides migration speed is affected by the porosity，permeability and diffusion coefficient of the matrix. The larger of these parameters are，the faster of the nuclides migration speed is. The nuclides migration is retarded by the matrix sorption，but the decaying coefficient has a limited influence on the nuclides migration. Thirdly，combining with 3D geological model and RockFlow，the fluid and nuclides migration are simulated；and the modeling results can provide references to the engineering design and safety assessment.

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3D GEOLOGICAL MODELLING IN JIUJING BLOCK，BEISHAN AREA，GANSU PROVINCE AND APPLICATION OF ROCKFLOW TO NUCLIDES MIGRATION SIMULATION

3D GEOLOGICAL MODELLING IN JIUJING BLOCK，BEISHAN AREA，GANSU PROVINCE AND APPLICATION OF ROCKFLOW TO NUCLIDES MIGRATION SIMULATION

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2007, 26 (S2): -3989 doi:
Full Text:

[PDF 420 KB] (636)

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Show Abstract

Through analyzing the geological structure，hydrogeology，geophysics and borehole data in Jiujing block，a simple 3D geological model was constructed by using the correspondence software for Jiujing block，Beishan area，Gansu Province. On the basis of the 3D faults stable fluid field，the 2D matrix diffusion and sorption，the nuclides decay were calculated and simulated by using RockFlow. Simultaneously，the underground fluid and nuclides migration in the matrix and fault were simulated，and the temporal and spatial distributions of underground fluid and nuclides were also studied. The result shows that the 3D geological model is a very useful site assessment method，from which the spatial distribution of the host rock and faults can be displayed directly. Secondly，the key migration channel of nuclides is fracture；and the nuclides migration speed is affected by the porosity，permeability and diffusion coefficient of the matrix. The larger of these parameters are，the faster of the nuclides migration speed is. The nuclides migration is retarded by the matrix sorption，but the decaying coefficient has a limited influence on the nuclides migration. Thirdly，combining with 3D geological model and RockFlow，the fluid and nuclides migration are simulated；and the modeling results can provide references to the engineering design and safety assessment.

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ISOTOPE ANALYSIS OF GROUNDWATER IN YEMAQUAN CANDIDATE SITE OF CHINA¢S HIGH-LEVEL RADIOACTIVE WASTE REPOSITORY

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2007, 26 (S2): -3995 doi:
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[PDF 367 KB] (691)

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Yemaquan district，one of the important candidate sites for China¢s high-level radioactive waste repository，is located in the Beishan area，Gansu Province，Northwest China. The granite is widely distributed in this district and it will be a good host rock for a high-level radioactive waste disposal repository. In order to understand the hydrogeological conditions and to evaluate if the district is a suitable/unsuitable site for a repository，the isotopic hydrogeological investigation and research were carried out during last decade. According to the field investigation and the analysis of the stable isotopes of hydrogen and oxygen，it is concluded that both shallow groundwater and deep groundwater are of meteoric origin. The shallow groundwater is recharged mainly by modern and local precipitation，and the deep groundwater may be originated from regional precipitation at higher elevation. In addition，from the tritium data of groundwater in the district，it is also found that the shallow groundwater system is relatively open；and the ability of water circulation is more capable than that of deep groundwater system.

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ISOTOPE ANALYSIS OF GROUNDWATER IN YEMAQUAN CANDIDATE SITE OF CHINA¢S HIGH-LEVEL RADIOACTIVE WASTE REPOSITORY

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2007, 26 (S2): -3995 doi:
Full Text:

[PDF 367 KB] (737)

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Show Abstract

Yemaquan district，one of the important candidate sites for China¢s high-level radioactive waste repository，is located in the Beishan area，Gansu Province，Northwest China. The granite is widely distributed in this district and it will be a good host rock for a high-level radioactive waste disposal repository. In order to understand the hydrogeological conditions and to evaluate if the district is a suitable/unsuitable site for a repository，the isotopic hydrogeological investigation and research were carried out during last decade. According to the field investigation and the analysis of the stable isotopes of hydrogen and oxygen，it is concluded that both shallow groundwater and deep groundwater are of meteoric origin. The shallow groundwater is recharged mainly by modern and local precipitation，and the deep groundwater may be originated from regional precipitation at higher elevation. In addition，from the tritium data of groundwater in the district，it is also found that the shallow groundwater system is relatively open；and the ability of water circulation is more capable than that of deep groundwater system.

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GEOLOGICAL CHARACTERS OF XINCHANG SECTION IN PRE-SELECTED BEISHAN REGION FOR HIGH-LEVEL RADIOACTIVE WASTE DISPOSAL

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2007, 26 (S2): -4000 doi:
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[PDF 300 KB] (707)

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This paper presents the geology of Xinchang section，one of the candidate areas in Beishan region in Gansu Province，China，for disposal of high-level radioactive waste；and the latest progress in the field of site selection in China is also introduced. With the help of TM satellite image interpretation and geological survey，space-time characteristics of the granite and faults in Xinchang section are investigated. According to the criteria and methodology of intrusive rock hierarchical unit，there are 3 granite super-units and 3 dependent units. Forty sets of faults are recognized and their scale，attitude，mechanical property and fracture strength are investigated. Based on the above results and the criteria adopted from other countries，two blocks，i.e. Jijicao and Xinchang，are selected. With the help of high resolution satellite image(i.e. Quick Bird in U.S.A.) interpretation and surface engineering exposure，border faults and inner faults of these two blocks are investigated. Dominant group，average spacing and average length of joints are carried out with statistical analysis using data measured from 837 outcrops in these two blocks. As a result，both blocks can be regarded as candidate sites for high-level radioactive waste repository；and next research stage，e.g. borehole survey，is under operation. In addition，it is proven that the block selection is such an efficient method that it can provide more detailed data for the next borehole survey.

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GEOLOGICAL CHARACTERS OF XINCHANG SECTION IN PRE-SELECTED BEISHAN REGION FOR HIGH-LEVEL RADIOACTIVE WASTE DISPOSAL

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2007, 26 (S2): -4000 doi:
Full Text:

[PDF 300 KB] (893)

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Show Abstract

This paper presents the geology of Xinchang section，one of the candidate areas in Beishan region in Gansu Province，China，for disposal of high-level radioactive waste；and the latest progress in the field of site selection in China is also introduced. With the help of TM satellite image interpretation and geological survey，space-time characteristics of the granite and faults in Xinchang section are investigated. According to the criteria and methodology of intrusive rock hierarchical unit，there are 3 granite super-units and 3 dependent units. Forty sets of faults are recognized and their scale，attitude，mechanical property and fracture strength are investigated. Based on the above results and the criteria adopted from other countries，two blocks，i.e. Jijicao and Xinchang，are selected. With the help of high resolution satellite image(i.e. Quick Bird in U.S.A.) interpretation and surface engineering exposure，border faults and inner faults of these two blocks are investigated. Dominant group，average spacing and average length of joints are carried out with statistical analysis using data measured from 837 outcrops in these two blocks. As a result，both blocks can be regarded as candidate sites for high-level radioactive waste repository；and next research stage，e.g. borehole survey，is under operation. In addition，it is proven that the block selection is such an efficient method that it can provide more detailed data for the next borehole survey.

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EFFECTS OF INCREASING WORKING FACE¢S LENGTH ON UNDERGROUND PRESSURE BEHAVIORS OF MINING SUPER-HIGH FACES UNDER SHALLOW COAL SEAM

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2007, 26 (S2): -4007 doi:
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[PDF 276 KB] (822)

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By the industrial mining experiments and observed data of working faces No.51101(240 m in length) and No.51104(300 m in length) in Shangwan coal mine of Shenfu—Dongsheng mining district，the effects of increasing face¢s length on underground pressure¢s behaviors were explored，and the conclusions are drawn as follows：(1) weighting span becomes shorter；(2) cycle weighting strength is relaxed；(3) the rock pressure distribution is shown that the quadric parabola relations can be used for the working face¢s middle point as symmetrical axis(i.e. coordinate origin)；(4) the regression relation between maximum resistances and initial ones is liner；and (5) the support¢s loads in non-weighting period and underground pressure behavior with increasing face¢s length are enhanced，and roof weighting impact load was larger than the support¢s maximum resistance for large mining height and supper-long faces.

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EFFECTS OF INCREASING WORKING FACE¢S LENGTH ON UNDERGROUND PRESSURE BEHAVIORS OF MINING SUPER-HIGH FACES UNDER SHALLOW COAL SEAM

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2007, 26 (S2): -4007 doi:
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[PDF 276 KB] (709)

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By the industrial mining experiments and observed data of working faces No.51101(240 m in length) and No.51104(300 m in length) in Shangwan coal mine of Shenfu—Dongsheng mining district，the effects of increasing face¢s length on underground pressure¢s behaviors were explored，and the conclusions are drawn as follows：(1) weighting span becomes shorter；(2) cycle weighting strength is relaxed；(3) the rock pressure distribution is shown that the quadric parabola relations can be used for the working face¢s middle point as symmetrical axis(i.e. coordinate origin)；(4) the regression relation between maximum resistances and initial ones is liner；and (5) the support¢s loads in non-weighting period and underground pressure behavior with increasing face¢s length are enhanced，and roof weighting impact load was larger than the support¢s maximum resistance for large mining height and supper-long faces.

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NUMERICAL SIMULATION STUDY ON WATER INRUSH MECHANISM FROM COLLAPSE COLUMN

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2007, 26 (S2): -4013 doi:
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[PDF 411 KB] (824)

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Based on the study of water inrush mechanism from coal floor in coal mining above confined aquifer， the water inrush mechanism and law were studied by using ANSYS through translating solid-fluid coupling equations into thermal analysis problem. Taking the Wuyang mine of Lu¢an coal mining administration geology as an example，the comparison of coal seam floor¢s stress，strain and water pressure distribution rules of working face is studied when the working faces keep away from or are close to collapse column. The results show that stress，displacement and seepage field of surrounding rock mass do not influence each other when working faces keep away from collapse column. With working face being pushed close to working face，alteration of the stress-strain curve，water level pressure of water-bearing structural zone in seepage field all will take place，and the approximate boundary distance is about 50 m. It is found that alteration of stress is small as working faces keep away from collapse column，and the degree of stress concentration remains stable. However，the distribution range expands and diffuses speedily to collapse column. The highest water level of water inrush from solid seepage is located at the 15–20 m backside of working face，so water inrush from concealed collapse column is commonly the water inrush lagged.

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NUMERICAL SIMULATION STUDY ON WATER INRUSH MECHANISM FROM COLLAPSE COLUMN

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2007, 26 (S2): -4013 doi:
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[PDF 411 KB] (669)

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Based on the study of water inrush mechanism from coal floor in coal mining above confined aquifer， the water inrush mechanism and law were studied by using ANSYS through translating solid-fluid coupling equations into thermal analysis problem. Taking the Wuyang mine of Lu¢an coal mining administration geology as an example，the comparison of coal seam floor¢s stress，strain and water pressure distribution rules of working face is studied when the working faces keep away from or are close to collapse column. The results show that stress，displacement and seepage field of surrounding rock mass do not influence each other when working faces keep away from collapse column. With working face being pushed close to working face，alteration of the stress-strain curve，water level pressure of water-bearing structural zone in seepage field all will take place，and the approximate boundary distance is about 50 m. It is found that alteration of stress is small as working faces keep away from collapse column，and the degree of stress concentration remains stable. However，the distribution range expands and diffuses speedily to collapse column. The highest water level of water inrush from solid seepage is located at the 15–20 m backside of working face，so water inrush from concealed collapse column is commonly the water inrush lagged.

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NUMERICAL SIMULATION OF 3D PERCOLATION MECHANISM
IN POROUS MEDIA

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2007, 26 (S2): -4019 doi:
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[PDF 254 KB] (711)

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The research methods of percolation in 3D porous media are presented. Based on VC++6.0，the software to simulate percolation is developed. The 3D percolation mechanism in porous media，the characteristics of percolation cluster by numerical simulation method，and the theory of renormalization are studied. The effective surface area rate is proposed.，and the achieved results indicate：(1) the number of cluster increases with the increasing porosity in the beginning and decreases at a later time when the value of porosity is 0.20，and the number of cluster has the maximum value；(2) with the increasing of porosity，the surface area of the largest cluster increases，and the value fleetness increases as the value of porosity is larger than percolation threshold；and (3) when porosity is 0.55，the surface area of the largest cluster reaches the maximum value，and the value of effective surface area rate is 0.98. When the value of porosity is 0.311 6，the percolation cluster is a random fractal and the fractal dimension can be deemed as D = 2.934.

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NUMERICAL SIMULATION OF 3D PERCOLATION MECHANISM
IN POROUS MEDIA

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2007, 26 (S2): -4019 doi:
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[PDF 254 KB] (812)

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The research methods of percolation in 3D porous media are presented. Based on VC++6.0，the software to simulate percolation is developed. The 3D percolation mechanism in porous media，the characteristics of percolation cluster by numerical simulation method，and the theory of renormalization are studied. The effective surface area rate is proposed.，and the achieved results indicate：(1) the number of cluster increases with the increasing porosity in the beginning and decreases at a later time when the value of porosity is 0.20，and the number of cluster has the maximum value；(2) with the increasing of porosity，the surface area of the largest cluster increases，and the value fleetness increases as the value of porosity is larger than percolation threshold；and (3) when porosity is 0.55，the surface area of the largest cluster reaches the maximum value，and the value of effective surface area rate is 0.98. When the value of porosity is 0.311 6，the percolation cluster is a random fractal and the fractal dimension can be deemed as D = 2.934.

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DUAL MEDIA MODEL FOR THERMO-HYDRO-MECHANICAL COUPLING AND 3D NUMERICAL SIMULATION

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2007, 26 (S2): -4024 doi:
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[PDF 635 KB] (1382)

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Based on the differential control equations of the coupled thermo-hydro-mechanical(THM) processes of dual media，this paper presented three-dimensional coupled model of dual media to research coupled THM of fractured rock masses. In the coupling model，the values of nodal displacement，water pressure and temperature were solved in different media. Strategy and methods to solve this mathematical model also were discussed. A three-dimensional FE codes for analysis of coupled THM processes of dual media were developed tentatively. Through the numerical computation for a coupling THM phenomenon in the heat exploitation of deep-seated HDR 2 200 m under the surface，it was shown：(1) coupling THM processes was obvious in the rock mass near injection wall；(2) trunk fractures will influence the distribution of seepage field，temperature field and stress field remarkably. Compared with hydro-mechanical coupled model and thermo-mechanical coupled model，the remarkable or unremarkable interactions between three fields were studied. It is also displayed：(1) dominant double coupling system occurs in the certain space time；(2) temperature field remarkably has effects on fracture seepage field under changeable temperature condition. The importance of coupled THM processes was highlighted.

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DUAL MEDIA MODEL FOR THERMO-HYDRO-MECHANICAL COUPLING AND 3D NUMERICAL SIMULATION

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2007, 26 (S2): -4024 doi:
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[PDF 635 KB] (1062)

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Based on the differential control equations of the coupled thermo-hydro-mechanical(THM) processes of dual media，this paper presented three-dimensional coupled model of dual media to research coupled THM of fractured rock masses. In the coupling model，the values of nodal displacement，water pressure and temperature were solved in different media. Strategy and methods to solve this mathematical model also were discussed. A three-dimensional FE codes for analysis of coupled THM processes of dual media were developed tentatively. Through the numerical computation for a coupling THM phenomenon in the heat exploitation of deep-seated HDR 2 200 m under the surface，it was shown：(1) coupling THM processes was obvious in the rock mass near injection wall；(2) trunk fractures will influence the distribution of seepage field，temperature field and stress field remarkably. Compared with hydro-mechanical coupled model and thermo-mechanical coupled model，the remarkable or unremarkable interactions between three fields were studied. It is also displayed：(1) dominant double coupling system occurs in the certain space time；(2) temperature field remarkably has effects on fracture seepage field under changeable temperature condition. The importance of coupled THM processes was highlighted.

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EXPERIMENTAL STUDY ON RELATIONS OF SUPPORT PRESSURE AND STABILITY OF SURROUNDING ROCK MASS IN DEEP TUNNELS

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2007, 26 (S2): -4032 doi:
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[PDF 319 KB] (665)

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The complete process of excavation，deformation and supporting of a deep tunnel was simulated with three physical models of the tunnel performed with a true triaxial test. During the experiment，the tunnel was excavated after a certain confining pressure was exerted on each model，and the supporting device of air bag was created to provide support pressure for the tunnel. The techniques of digital picture deformation measurement were applied to the processes of high definition color pictures of the model，through the displacement field of the rock surrounding，the tunnel could be obtained. Based on the analysis of the displacement field，the relation of support pressure and stability of the surrounding rock mass in deep tunnels was achieved，which would provide the theoretical and technical basis for stabilizing the deep tunnels.

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EXPERIMENTAL STUDY ON RELATIONS OF SUPPORT PRESSURE AND STABILITY OF SURROUNDING ROCK MASS IN DEEP TUNNELS

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2007, 26 (S2): -4032 doi:
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[PDF 319 KB] (610)

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The complete process of excavation，deformation and supporting of a deep tunnel was simulated with three physical models of the tunnel performed with a true triaxial test. During the experiment，the tunnel was excavated after a certain confining pressure was exerted on each model，and the supporting device of air bag was created to provide support pressure for the tunnel. The techniques of digital picture deformation measurement were applied to the processes of high definition color pictures of the model，through the displacement field of the rock surrounding，the tunnel could be obtained. Based on the analysis of the displacement field，the relation of support pressure and stability of the surrounding rock mass in deep tunnels was achieved，which would provide the theoretical and technical basis for stabilizing the deep tunnels.

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NUMERICAL SIMULATION RESEARCH ON ROCK MOVEMENT CAUSED BY SURFACE MINING AND UNDERGROUND MINING

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2007, 26 (S2): -4037 doi:
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[PDF 554 KB] (784)

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Illegal mining has a great influence on stability of mines. In the paper，two-dimensional numerical simulation on Jinshandian underground iron mine is carried out by using finite element method and discrete element method. The regulations of surface deformation and surrounding rock movement with/without illegal mining are obtained，respectively. The obtained results indicate that an elliptic disturbed zone is formed around underground gob and the major axis of ellipse is parallel with the tendency of the orebody. Gobs formed by illegal mining and underground mining will not connect. In addition，illegal mining has little influence on the size of underground disturbed zone. Because of stress redistribution caused by illegal mining，the size of surface subsidence increases near surface gob；and horizontal displacement of surface increases greatly，but the range of surface subsidence is almost found without change.

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NUMERICAL SIMULATION RESEARCH ON ROCK MOVEMENT CAUSED BY SURFACE MINING AND UNDERGROUND MINING

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2007, 26 (S2): -4037 doi:
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[PDF 554 KB] (872)

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Illegal mining has a great influence on stability of mines. In the paper，two-dimensional numerical simulation on Jinshandian underground iron mine is carried out by using finite element method and discrete element method. The regulations of surface deformation and surrounding rock movement with/without illegal mining are obtained，respectively. The obtained results indicate that an elliptic disturbed zone is formed around underground gob and the major axis of ellipse is parallel with the tendency of the orebody. Gobs formed by illegal mining and underground mining will not connect. In addition，illegal mining has little influence on the size of underground disturbed zone. Because of stress redistribution caused by illegal mining，the size of surface subsidence increases near surface gob；and horizontal displacement of surface increases greatly，but the range of surface subsidence is almost found without change.

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VISCOPLASTICITY MODEL OF ROCK MASS AT LARGE STRAINS AND ITS APPLICATION TO DEEP MINING

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2007, 26 (S2): -4044 doi:
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[PDF 475 KB] (550)

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In the present study，a phenomenological constitutive model of viscoplasticity at large strains capable of describing the strain localization problems together with nonlocal approach is developed，which generalizes the classical Perzyna or Duvaut-Lions models to large strains. The nonlocalization for local plastic variable under modeling is implemented by means of numerical weighted operation concerned with a representative size，which characterizes the micro- and meso-effects of material. The model is performed based on a minimum number of hypothesis，including the multiplicative decomposition of deformation gradient，a definition of the elastic domain and finally a penalty-like，viscoplastic regularization of the principle of maximum plastic dissipation. The model is also extended to involve the isotropic and kinematic hardening or softening. Mesh-sensitivity analyses of nonlocalization at large strain along with the refinement of corresponding element size are also discussed. Several illustrative numerical examples that include an unconfined compression test compared with the simulations by FLAC3D and analyses of rheological effect for a typical deep mine after excavation are presented. It demonstrates that the ability of the proposed model to remove the deficiencies of some presently used strain-softening models is acceptable.

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VISCOPLASTICITY MODEL OF ROCK MASS AT LARGE STRAINS AND ITS APPLICATION TO DEEP MINING

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2007, 26 (S2): -4044 doi:
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[PDF 475 KB] (694)

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Show Abstract

In the present study，a phenomenological constitutive model of viscoplasticity at large strains capable of describing the strain localization problems together with nonlocal approach is developed，which generalizes the classical Perzyna or Duvaut-Lions models to large strains. The nonlocalization for local plastic variable under modeling is implemented by means of numerical weighted operation concerned with a representative size，which characterizes the micro- and meso-effects of material. The model is performed based on a minimum number of hypothesis，including the multiplicative decomposition of deformation gradient，a definition of the elastic domain and finally a penalty-like，viscoplastic regularization of the principle of maximum plastic dissipation. The model is also extended to involve the isotropic and kinematic hardening or softening. Mesh-sensitivity analyses of nonlocalization at large strain along with the refinement of corresponding element size are also discussed. Several illustrative numerical examples that include an unconfined compression test compared with the simulations by FLAC3D and analyses of rheological effect for a typical deep mine after excavation are presented. It demonstrates that the ability of the proposed model to remove the deficiencies of some presently used strain-softening models is acceptable.

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3D GEOMECHANICAL MODEL TEST RESEARCH ON STABILITY AND SUPPORTING FOR SURROUNDING ROCK MASS OF A LARGE-SCALE DIVERSION TUNNEL

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2007, 26 (S2): -4051 doi:
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[PDF 566 KB] (681)

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Diversion tunnel is a new type tunnel structure. There is not any technical standard of design and construction for the diversion tunnel at present. A large-scale diversion tunnel of highway under construction is studied through the 3D geomechanical model test method in order to understand stress and deformation situations of surrounding rock mass of the diversion tunnel under excavation state. The changing laws of stress and displacement around the tunnel and the failure mechanism for the surrounding rock mass of tunnel have been effectively revealed after test. The design and limit load-bearing safety reliability for the diversion tunnel have also been achieved. According to results of the model test，some useful suggestions and conclusions for the optimization design and construction of the diversion tunnel have been proposed.

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3D GEOMECHANICAL MODEL TEST RESEARCH ON STABILITY AND SUPPORTING FOR SURROUNDING ROCK MASS OF A LARGE-SCALE DIVERSION TUNNEL

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2007, 26 (S2): -4051 doi:
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[PDF 566 KB] (667)

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Show Abstract

Diversion tunnel is a new type tunnel structure. There is not any technical standard of design and construction for the diversion tunnel at present. A large-scale diversion tunnel of highway under construction is studied through the 3D geomechanical model test method in order to understand stress and deformation situations of surrounding rock mass of the diversion tunnel under excavation state. The changing laws of stress and displacement around the tunnel and the failure mechanism for the surrounding rock mass of tunnel have been effectively revealed after test. The design and limit load-bearing safety reliability for the diversion tunnel have also been achieved. According to results of the model test，some useful suggestions and conclusions for the optimization design and construction of the diversion tunnel have been proposed.

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STRUCTURAL HIERARCHY KINETIC NATURE OF DEFORMATION
AND FRACTURE OF GEOMEDIUM AND SEISMIC FORECASTING

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2007, 26 (S2): -4060 doi:
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[PDF 281 KB] (675)

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This paper gives an overview of achievements in forecasting rock impact and earthquakes based on the concentration criterion and the evolution law of temporal parameters of dynamic events in fracture processes in the last 30 years. At first，the physico-mechanical meaning of concentration criterion is clarified. Then，the self-similarity of deformation and fracture of rock mass at different structural hierarchies and the fractal natures of the concentration parameters of fracture are introduced. At last，the approaches of forecasting of rock impacts，micro-seismicity in mining regions and earthquakes with different energies and the efficiency of these approaches are overviewed. It is believed that the overview will be helpful for the scholars in this area in China.

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STRUCTURAL HIERARCHY KINETIC NATURE OF DEFORMATION
AND FRACTURE OF GEOMEDIUM AND SEISMIC FORECASTING

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2007, 26 (S2): -4060 doi:
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[PDF 281 KB] (710)

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This paper gives an overview of achievements in forecasting rock impact and earthquakes based on the concentration criterion and the evolution law of temporal parameters of dynamic events in fracture processes in the last 30 years. At first，the physico-mechanical meaning of concentration criterion is clarified. Then，the self-similarity of deformation and fracture of rock mass at different structural hierarchies and the fractal natures of the concentration parameters of fracture are introduced. At last，the approaches of forecasting of rock impacts，micro-seismicity in mining regions and earthquakes with different energies and the efficiency of these approaches are overviewed. It is believed that the overview will be helpful for the scholars in this area in China.

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QUANTITATIVE STUDY ON STRESS-STRAIN HYSTERETIC BEHAVIORS IN ROCKS

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2007, 26 (S2): -4066 doi:
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[PDF 414 KB] (603)

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Hysteresis loop of rock subjected to cyclic loading is the phenomenon of nonclassical nonlinearity. The purpose of this paper is to discuss the quantitative expression of hysteretic behaviors in rocks by introducing a measurement of X-shaped tangent modulus of stress-strain hysteresis loop. The stress-strain hysteresis loop is cusped，which is the consequence of phase change of strain at the reverse point of loading and unloading under the applied external sinusoidal force. Tangent modulus and tangent Poisson¢s ratio are in asymmetrical X-shaped as the function of axial strain under cyclic loading，and they both are discontinuous at the reverse point of loading and unloading. Hysteresis observed in rock¢s stress-strain diagram under cyclic loading condition is the consequence of phase difference between the stress and its correspondent strain. Theoretical calculation，based on the above observed fact and a series of uniaxial stress cycling measurements for sandstone and marble，demonstrates the deterministic relationship between inclination of X-shaped tangent modulus of hysteresis loopq¢ and its dissipation angle. Inclination of X-shaped tangent modulus of hysteresis loop q ¢ can be used to reflect nonlinear stress-strain hysteretic degree in rock and rock-like materials.

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QUANTITATIVE STUDY ON STRESS-STRAIN HYSTERETIC BEHAVIORS IN ROCKS

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2007, 26 (S2): -4066 doi:
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[PDF 414 KB] (968)

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Hysteresis loop of rock subjected to cyclic loading is the phenomenon of nonclassical nonlinearity. The purpose of this paper is to discuss the quantitative expression of hysteretic behaviors in rocks by introducing a measurement of X-shaped tangent modulus of stress-strain hysteresis loop. The stress-strain hysteresis loop is cusped，which is the consequence of phase change of strain at the reverse point of loading and unloading under the applied external sinusoidal force. Tangent modulus and tangent Poisson¢s ratio are in asymmetrical X-shaped as the function of axial strain under cyclic loading，and they both are discontinuous at the reverse point of loading and unloading. Hysteresis observed in rock¢s stress-strain diagram under cyclic loading condition is the consequence of phase difference between the stress and its correspondent strain. Theoretical calculation，based on the above observed fact and a series of uniaxial stress cycling measurements for sandstone and marble，demonstrates the deterministic relationship between inclination of X-shaped tangent modulus of hysteresis loopq¢ and its dissipation angle. Inclination of X-shaped tangent modulus of hysteresis loop q ¢ can be used to reflect nonlinear stress-strain hysteretic degree in rock and rock-like materials.

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AN IOWGA OPERATOR-BASED DAM SAFETY MONITORING COMBINATION FORECASTING MODEL

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2007, 26 (S2): -4074 doi:
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[PDF 250 KB] (594)

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The concept of induced ordered weighted geometric averaging(IOWGA) operator is introduced in this paper，and a new dam safety monitoring combination forecasting model based on IOWGA operator is put forward. In this combination model，each single forecasting model is endowed with weights orderly according to its prediction accuracy in each point. Case study shows that the proposed combination forecasting model is superior to the traditional weighted arithmetic averaging combination forecasting model and each single forecasting model. It has high prediction accuracy and it is effective and credible as well in prediction of dam safety monitoring.

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AN IOWGA OPERATOR-BASED DAM SAFETY MONITORING COMBINATION FORECASTING MODEL

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2007, 26 (S2): -4074 doi:
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[PDF 250 KB] (656)

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The concept of induced ordered weighted geometric averaging(IOWGA) operator is introduced in this paper，and a new dam safety monitoring combination forecasting model based on IOWGA operator is put forward. In this combination model，each single forecasting model is endowed with weights orderly according to its prediction accuracy in each point. Case study shows that the proposed combination forecasting model is superior to the traditional weighted arithmetic averaging combination forecasting model and each single forecasting model. It has high prediction accuracy and it is effective and credible as well in prediction of dam safety monitoring.

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STUDY ON SETTLEMENT BEHAVIOR OF SUPER WIDE SUBGRADE

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2007, 26 (S2): -4079 doi:
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[PDF 256 KB] (702)

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The width of highway is an important factor for the stress state of subgrade，and the settlement distribution of subgrade changes with the width of highway. According to the observed data of settlement in Xinxiang—Zhenzhou section of Beijing—Zhuhai Highway，the settlement distribution along the width of narrow subgrade was of a parabolic curve，but the distribution of wide subgrade was saddle-shaped. The finite element method was applied to the analysis of the influence of width on the settlement distribution by employing the Duncan-Chang constitutional model. Numerical results indicated that the distance between the maximum settlement point and the center of subgrade was proportional to the width of half-subgrade. When widths of the half-subgrade increased from 20 m to 66 m，the ratios of distance between the maximum settlement point and the centre of subgrade to the width of half-subgrade increased from 0.0 to 0.6.

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STUDY ON SETTLEMENT BEHAVIOR OF SUPER WIDE SUBGRADE

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2007, 26 (S2): -4079 doi:
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[PDF 256 KB] (679)

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The width of highway is an important factor for the stress state of subgrade，and the settlement distribution of subgrade changes with the width of highway. According to the observed data of settlement in Xinxiang—Zhenzhou section of Beijing—Zhuhai Highway，the settlement distribution along the width of narrow subgrade was of a parabolic curve，but the distribution of wide subgrade was saddle-shaped. The finite element method was applied to the analysis of the influence of width on the settlement distribution by employing the Duncan-Chang constitutional model. Numerical results indicated that the distance between the maximum settlement point and the center of subgrade was proportional to the width of half-subgrade. When widths of the half-subgrade increased from 20 m to 66 m，the ratios of distance between the maximum settlement point and the centre of subgrade to the width of half-subgrade increased from 0.0 to 0.6.

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DETERMINATION OF END BEARING CAPACITY OF PILE WITH DOUBLE-SHEAR SLIP-LINE THEORY

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2007, 26 (S2): -4084 doi:
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[PDF 222 KB] (567)

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The end bearing capacity of pile based on Mohr-Coulomb strength criterion does not consider the effect of intermediate principal stress，so that the calculated bearing capacity may be rather different from practical data. This paper recommended a method to determine the end bearing capacity of pile in sandy clay by double-shear slip-line theory，which can consider the difference between the tension strength and compression strength of soil material. The effect of intermediate principal stress was included in the formula，which was based on some reasonable hypotheses. It was developed in a way similar to that proposed by A. Serrano and C. Olalla in the determination of end bearing capacity of pile in rock foundation according to the theory of plasticity. In the calculation process，the plastic area was analyzed as a two-dimensional medium using the slip-line method. The overburden pressure，which was assumed to be uniformly distributed，exerted on the virtual surface(boundary 1)，together with the potential external loads that are rested upon it. And then，the stress on boundary 2 was obtained from the stress on boundary 1 by using transferring formula of slip-line. Analyses of the project data collected in the area of Wuhan City were carried out with Mohr-Coulomb strength criterion and the recommended method separately. The results show that the recommended method，in which the effect of intermediate principal stress was considered，was closer to the actual projects. So this method for calculating the end bearing capacity is found to be more useful.

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DETERMINATION OF END BEARING CAPACITY OF PILE WITH DOUBLE-SHEAR SLIP-LINE THEORY

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2007, 26 (S2): -4084 doi:
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[PDF 222 KB] (632)

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The end bearing capacity of pile based on Mohr-Coulomb strength criterion does not consider the effect of intermediate principal stress，so that the calculated bearing capacity may be rather different from practical data. This paper recommended a method to determine the end bearing capacity of pile in sandy clay by double-shear slip-line theory，which can consider the difference between the tension strength and compression strength of soil material. The effect of intermediate principal stress was included in the formula，which was based on some reasonable hypotheses. It was developed in a way similar to that proposed by A. Serrano and C. Olalla in the determination of end bearing capacity of pile in rock foundation according to the theory of plasticity. In the calculation process，the plastic area was analyzed as a two-dimensional medium using the slip-line method. The overburden pressure，which was assumed to be uniformly distributed，exerted on the virtual surface(boundary 1)，together with the potential external loads that are rested upon it. And then，the stress on boundary 2 was obtained from the stress on boundary 1 by using transferring formula of slip-line. Analyses of the project data collected in the area of Wuhan City were carried out with Mohr-Coulomb strength criterion and the recommended method separately. The results show that the recommended method，in which the effect of intermediate principal stress was considered，was closer to the actual projects. So this method for calculating the end bearing capacity is found to be more useful.

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EXPERIMENTAL STUDY ON MAXIMUM DRY DENSITY OF OVERDIAMETER COARSE-GRAINED EARTH

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2007, 26 (S2): -4090 doi:
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[PDF 175 KB] (679)

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Research is carried out for the maximum dry density of each residue earth material，through result analysis，it is found that there exists the linear relation between the maximum dry density and quantity of the sorting and the surplus. Thus，the idea of the maximum dry density that can be obtained indirectly from the extension of coarse-grained earth series，is proposed.

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EXPERIMENTAL STUDY ON MAXIMUM DRY DENSITY OF OVERDIAMETER COARSE-GRAINED EARTH

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2007, 26 (S2): -4090 doi:
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[PDF 175 KB] (1098)

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Research is carried out for the maximum dry density of each residue earth material，through result analysis，it is found that there exists the linear relation between the maximum dry density and quantity of the sorting and the surplus. Thus，the idea of the maximum dry density that can be obtained indirectly from the extension of coarse-grained earth series，is proposed.

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EVALUATION OF COLLAPSIBLE LOESS SUBGRADE TREATED BY DYNAMIC COMPACTION

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2007, 26 (S2): -4095 doi:
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[PDF 240 KB] (852)

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Through analyzing the data of the static loading tests(SLT) and the cone penetration tests(CPT)，which are on the collapsible loess subgrade treated by dynamic compaction，the corresponding formulae of the characteristic value of dynamic subgrade bearing capacity fak and the minimum mean value of cone resistance qc are obtained. Accordingly，after method and standard of quantitative evaluation of dynamic subgrade bearing capacity are established on the basis of design requirement，and the dynamic subgrade bearing capacity is quantitatively evaluated using the CPT. Weak layers are found and areas with weak layers are determined in the dynamic subgrade. The collapsibility of dynamic subgrade is quantitatively appraised by the test method of soil samples from the investigation wells，and larger remnant collapses are found in 2 investigation wells in the dynamic subgrade. The cause of formation of weak layers is analyzed and lime piles are consdiered to eliminate the potential dangers in the areas with weak layers. Effective reinforcement depth and influencing depth after dynamic compaction are accurately decided using the CPT on the basis of subgrade bearing capacity standards，the effective reinforcement depth after dynamic compaction is also decided using soil test method on the basis of remnant collapse standards，and the difference of effective reinforcement depths between both methods is found.

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EVALUATION OF COLLAPSIBLE LOESS SUBGRADE TREATED BY DYNAMIC COMPACTION

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2007, 26 (S2): -4095 doi:
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[PDF 240 KB] (708)

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Through analyzing the data of the static loading tests(SLT) and the cone penetration tests(CPT)，which are on the collapsible loess subgrade treated by dynamic compaction，the corresponding formulae of the characteristic value of dynamic subgrade bearing capacity fak and the minimum mean value of cone resistance qc are obtained. Accordingly，after method and standard of quantitative evaluation of dynamic subgrade bearing capacity are established on the basis of design requirement，and the dynamic subgrade bearing capacity is quantitatively evaluated using the CPT. Weak layers are found and areas with weak layers are determined in the dynamic subgrade. The collapsibility of dynamic subgrade is quantitatively appraised by the test method of soil samples from the investigation wells，and larger remnant collapses are found in 2 investigation wells in the dynamic subgrade. The cause of formation of weak layers is analyzed and lime piles are consdiered to eliminate the potential dangers in the areas with weak layers. Effective reinforcement depth and influencing depth after dynamic compaction are accurately decided using the CPT on the basis of subgrade bearing capacity standards，the effective reinforcement depth after dynamic compaction is also decided using soil test method on the basis of remnant collapse standards，and the difference of effective reinforcement depths between both methods is found.

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CALCULATION OF DIFFERENCE IN TEMPERATURE BETWEEN SUNNY SLOPE AND SHADY SLOPE ALONG RAILWAYS IN PERMAFROST REGIONS IN QINGHAI—TIBET PLATEAU

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2007, 26 (S2): -4102 doi:
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[PDF 231 KB] (643)

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The temperature variations are the hot issues in freeze soil mechanics. After roadbed being built in permafrost regions，there will be dissimilar thermal regime on slopes because of different roadbed orientations，which will lead to distinct thawing morphologies under the embankment. In view of the specific natural environment of Qinghai—Tibet Plateau，field monitored ground temperature and meteorological data are difficult to obtain，therefore a regression equation by statistics method between the temperature difference of shallow ground(0.5m) and solar radiation difference on slopes is adopted，and the equation is validated，which can better disclose the mean annual temperature difference on slopes of railway roadbed along different routes in Beiluhe. The equation may provide the dependable science basis for the road construction and maintenance on permafrost regions of plateau.

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CALCULATION OF DIFFERENCE IN TEMPERATURE BETWEEN SUNNY SLOPE AND SHADY SLOPE ALONG RAILWAYS IN PERMAFROST REGIONS IN QINGHAI—TIBET PLATEAU

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2007, 26 (S2): -4102 doi:
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[PDF 231 KB] (724)

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Show Abstract

The temperature variations are the hot issues in freeze soil mechanics. After roadbed being built in permafrost regions，there will be dissimilar thermal regime on slopes because of different roadbed orientations，which will lead to distinct thawing morphologies under the embankment. In view of the specific natural environment of Qinghai—Tibet Plateau，field monitored ground temperature and meteorological data are difficult to obtain，therefore a regression equation by statistics method between the temperature difference of shallow ground(0.5m) and solar radiation difference on slopes is adopted，and the equation is validated，which can better disclose the mean annual temperature difference on slopes of railway roadbed along different routes in Beiluhe. The equation may provide the dependable science basis for the road construction and maintenance on permafrost regions of plateau.

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APPLICATION AND VERIFICATION OF COMPOSITE ELEMENT METHOD IN THE ROCK BOLT CRANE GIRDER OF UNDERGROUND POWERHOUSE

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2007, 26 (S2): -4108 doi:
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[PDF 293 KB] (588)

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The comparative study of the composite element method(CEM) and the conventional finite element method(FEM) is carried out for the rock bolt crane girder of an underground powerhouse. The attention is paid to the portion of the contact face between girder and surrounding rock masses，the contact faces between bolts and surrounding rock masses，as well as to the portion where rock bolt penetrates the contact face. The excavation procedure of the underground cavern，the installation procedure and operation procedure of the rock bolt crane girder are simulated；and the characteristics and efficiency of the CEM and FEM are presented. It is shown that the results by the CEM are close to those of conventional FEM in the explicit simulation of reinforced jointed rock masses；the CEM is able to provide more detailed messages concerning the stress and deformation；and the CEM has the advantages in the simplification of pre-process. The study also shows that since the complicated pre-process works in the FEM are replaced by the complicated computation works in the CEM，more computation time is required in the application of the CEM.

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APPLICATION AND VERIFICATION OF COMPOSITE ELEMENT METHOD IN THE ROCK BOLT CRANE GIRDER OF UNDERGROUND POWERHOUSE

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2007, 26 (S2): -4108 doi:
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[PDF 293 KB] (633)

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The comparative study of the composite element method(CEM) and the conventional finite element method(FEM) is carried out for the rock bolt crane girder of an underground powerhouse. The attention is paid to the portion of the contact face between girder and surrounding rock masses，the contact faces between bolts and surrounding rock masses，as well as to the portion where rock bolt penetrates the contact face. The excavation procedure of the underground cavern，the installation procedure and operation procedure of the rock bolt crane girder are simulated；and the characteristics and efficiency of the CEM and FEM are presented. It is shown that the results by the CEM are close to those of conventional FEM in the explicit simulation of reinforced jointed rock masses；the CEM is able to provide more detailed messages concerning the stress and deformation；and the CEM has the advantages in the simplification of pre-process. The study also shows that since the complicated pre-process works in the FEM are replaced by the complicated computation works in the CEM，more computation time is required in the application of the CEM.

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CONTRASTIVE ANALYSIS OF STABILITY OF BLOCK IN LARGE UNDERGROUND CAVERNS UNDER CONDITIONS OF EXCAVATION AND UNLOADING

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2007, 26 (S2): -4115 doi:
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[PDF 416 KB] (693)

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3D numerical simulation of typical sidewall and crown blocks is carried out for underground powerhouse of the Three Gorges Project. The following results can be drawn. (1) The sidewall block is in unloading stress state in vertical direction(y-direction) and horizontally perpendicular to powerhouse axis(x-direction)，especially the latter and its main deformation is horizontally unloading rebound to excavated zone. (2) The compressive stress of the crown block is gradually increased in x-direction along with excavation，but the vertical stress is in unloading state in initial excavation stages and gradually increases along with latter excavation. Its main deformation is compressive in x-direction，but in y-direction，the lower part of block goes down because of unloading and the upper part goes up because of x-direction extrusion. (3) The stress-deformation field of blocks in process of excavation is beneficial to the stability of crown blocks，but unfavorable to the sidewall blocks. So，the calculation result based on rigid body limit equilibrium theory is over-estimated to sidewall blocks，but conservative to crown blocks. (4) The authors present that the method of qualitatively judging block general stability by its deformation and of quantificationally evaluating local stability by plastic zone characteristics.

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CONTRASTIVE ANALYSIS OF STABILITY OF BLOCK IN LARGE UNDERGROUND CAVERNS UNDER CONDITIONS OF EXCAVATION AND UNLOADING

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2007, 26 (S2): -4115 doi:
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[PDF 416 KB] (650)

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3D numerical simulation of typical sidewall and crown blocks is carried out for underground powerhouse of the Three Gorges Project. The following results can be drawn. (1) The sidewall block is in unloading stress state in vertical direction(y-direction) and horizontally perpendicular to powerhouse axis(x-direction)，especially the latter and its main deformation is horizontally unloading rebound to excavated zone. (2) The compressive stress of the crown block is gradually increased in x-direction along with excavation，but the vertical stress is in unloading state in initial excavation stages and gradually increases along with latter excavation. Its main deformation is compressive in x-direction，but in y-direction，the lower part of block goes down because of unloading and the upper part goes up because of x-direction extrusion. (3) The stress-deformation field of blocks in process of excavation is beneficial to the stability of crown blocks，but unfavorable to the sidewall blocks. So，the calculation result based on rigid body limit equilibrium theory is over-estimated to sidewall blocks，but conservative to crown blocks. (4) The authors present that the method of qualitatively judging block general stability by its deformation and of quantificationally evaluating local stability by plastic zone characteristics.

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STUDY ON DAMAGE AND BIFURCATION PROPERTIES OF SOME GRANITES BASED ON TRIAXIAL CREEP EXPERIMENT

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2007, 26 (S2): -4123 doi:
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[PDF 461 KB] (521)

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The creep properties of granite specimen are studied under triaxial compression creep experiment with the method of step loading，and the experimental results show that there exists a stress threshold in the creep deformation of rock from stable creep phase to accelerating creep phase. If the applied load is lower than the threshold，the initial microcracks and pores in rock are compacted under the lower stress level and the microcosmic linear visco-elastic deformation will come into being in the microstructure of rock，so the creep rate of rock is uniform and the deformation will tend towards a steady value，and the rheological parameters are invariable under the lower stress level；when the applied load is bigger enough to exceed the threshold，a mass of microcracks come into being，grow quickly，and the damage evolvement is rapid，this will induce the change of rheological parameters of rock. To obtain the value of this stress threshold，the triaxial compression creep experiment of rock is simulated with the method of three-dimensional numerical simulation and the stress threshold is obtained. The damage variables are introduced into the generalized Kelvin model，and the corresponding damage evolution equations which are able to reflect the characteristics of the accelerating creep phase of rock are set up. Furthermore，by applying the bifurcation theory of solid mechanics，the bifurcation behavior of rock due to the change of rheological parameters after the deformation turning into the accelerating creep phase is studied，the rheological parameters，which cause the creep bifurcation behavior of rock，are determined and the bifurcation points are obtained. The results show that the calculated curve based on the effective initial elastic modulus considering damage factor agrees well with the experiment curve.

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STUDY ON DAMAGE AND BIFURCATION PROPERTIES OF SOME GRANITES BASED ON TRIAXIAL CREEP EXPERIMENT

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2007, 26 (S2): -4123 doi:
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[PDF 461 KB] (1127)

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Show Abstract

The creep properties of granite specimen are studied under triaxial compression creep experiment with the method of step loading，and the experimental results show that there exists a stress threshold in the creep deformation of rock from stable creep phase to accelerating creep phase. If the applied load is lower than the threshold，the initial microcracks and pores in rock are compacted under the lower stress level and the microcosmic linear visco-elastic deformation will come into being in the microstructure of rock，so the creep rate of rock is uniform and the deformation will tend towards a steady value，and the rheological parameters are invariable under the lower stress level；when the applied load is bigger enough to exceed the threshold，a mass of microcracks come into being，grow quickly，and the damage evolvement is rapid，this will induce the change of rheological parameters of rock. To obtain the value of this stress threshold，the triaxial compression creep experiment of rock is simulated with the method of three-dimensional numerical simulation and the stress threshold is obtained. The damage variables are introduced into the generalized Kelvin model，and the corresponding damage evolution equations which are able to reflect the characteristics of the accelerating creep phase of rock are set up. Furthermore，by applying the bifurcation theory of solid mechanics，the bifurcation behavior of rock due to the change of rheological parameters after the deformation turning into the accelerating creep phase is studied，the rheological parameters，which cause the creep bifurcation behavior of rock，are determined and the bifurcation points are obtained. The results show that the calculated curve based on the effective initial elastic modulus considering damage factor agrees well with the experiment curve.

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DYNAMIC ESTIMATION OF GEOMECHANICAL PARAMETERS
VIA ENSEMBLE KALMAN FILTER COUPLED WITH NUMERICAL ANALYSIS

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2007, 26 (S2): -4130 doi:
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[PDF 330 KB] (942)

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With respect to the uncertainty process，the ensemble Kalman filter(EnKF) is introduced，the geomechanical deformation is treated as a dynamic stochastic system，and the displacement observation is looked as the output to describe the state of system with ensemble Kalmen filter. Furthermore，it is coupled with numerical modeling to cope with the uncertainty. Thus，the dynamical estimation of geomechanical parameters is performed，the parameter and its uncertainty are simultaneously obtained. The numerical examples show that the can effectively deal with the measured data polluted by noise，and can dynamically tract with the mechanical response of rock/soil mass. Compared with the conventional optimization algorithm，the EnKF shows the better character of real time and reliability because it can provide the inversion results and the posteriori

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DYNAMIC ESTIMATION OF GEOMECHANICAL PARAMETERS
VIA ENSEMBLE KALMAN FILTER COUPLED WITH NUMERICAL ANALYSIS

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2007, 26 (S2): -4130 doi:
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[PDF 330 KB] (888)

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With respect to the uncertainty process，the ensemble Kalman filter(EnKF) is introduced，the geomechanical deformation is treated as a dynamic stochastic system，and the displacement observation is looked as the output to describe the state of system with ensemble Kalmen filter. Furthermore，it is coupled with numerical modeling to cope with the uncertainty. Thus，the dynamical estimation of geomechanical parameters is performed，the parameter and its uncertainty are simultaneously obtained. The numerical examples show that the can effectively deal with the measured data polluted by noise，and can dynamically tract with the mechanical response of rock/soil mass. Compared with the conventional optimization algorithm，the EnKF shows the better character of real time and reliability because it can provide the inversion results and the posteriori distribution of the priori information together.

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_{DYNAMICAL OPTIMAL ANCHORING DESIGN AND INFORMATION CONSTRUCTION OF DANBA LANDSLIDE}

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2007, 26 (S2): -4139 doi:
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[PDF 394 KB] (621)

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The Danba landslide is located on the rear of Danba town in Sichuan Province. The total volume is about 2.2×106 m3. The speed of deformation became obvious in October 2004，and accelerated in February 2005 with the maximum value reaching 5 cm per day and the landslide tending to slide entirely. If the whole landslide moved down，more than half of the Danba town would be destroyed. The related agencies organized the emergency aid and comprehensive remedial projects as soon as possible. The attention was paid to how to make good use of the monitoring data to analyze the genetic mechanism and the stability of the landslide，and to guide the design and construction of the prestressed anchoring work. The study shows that，by making use of the observed data of the surface displacement，the displacement in depth and the tension of anchor cables，not only the anchoring effect of cables can be evaluated，but also the design and construction options can be adjusted in time，which indicates that the monitoring plays a very important role in landslide treatment.

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_{DYNAMICAL OPTIMAL ANCHORING DESIGN AND INFORMATION CONSTRUCTION OF DANBA LANDSLIDE}

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2007, 26 (S2): -4139 doi:
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[PDF 394 KB] (706)

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The Danba landslide is located on the rear of Danba town in Sichuan Province. The total volume is about 2.2×106 m3. The speed of deformation became obvious in October 2004，and accelerated in February 2005 with the maximum value reaching 5 cm per day and the landslide tending to slide entirely. If the whole landslide moved down，more than half of the Danba town would be destroyed. The related agencies organized the emergency aid and comprehensive remedial projects as soon as possible. The attention was paid to how to make good use of the monitoring data to analyze the genetic mechanism and the stability of the landslide，and to guide the design and construction of the prestressed anchoring work. The study shows that，by making use of the observed data of the surface displacement，the displacement in depth and the tension of anchor cables，not only the anchoring effect of cables can be evaluated，but also the design and construction options can be adjusted in time，which indicates that the monitoring plays a very important role in landslide treatment.

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SENSITIVITY ANALYSIS OF MESH SIZE ON CRACK TIP¢S
STRESS INTENSITY FACTOR

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2007, 26 (S2): -4147 doi:
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[PDF 256 KB] (631)

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The stability of macrocrack in engineering was analyzed based on LEFM(linear elastic fracture mechanics) model；and the crack tip¢s stress intensity factor was calculated by displacement direct method. In response to the problems whether crack tip must be subdivided with fine-mesh and nodes¢ displacement were used to extrapolate the crack tip¢s stress intensity factor and so on，the sensitivity of mesh size on crack tip¢s stress intensity factor was analyzed. The following conclusion can be obtained. (1) When using displacement direct method to extrapolate the crack tip¢s stress intensity factor，it must ignore the nodal displacement near the crack tip and use the far field one；(2) If the 1/4 edge middle node(singular isoparametric element) was used near the crack tip，it could also obtain the satisfied result even with the coarse mesh，which will greatly reduce the computing workload. These findings were verified by the analyses of a typical three-point bent beam with cracks and the horizontal cracks of Longyangxia gravity arch dam. Then，base on LEFM model，the horizontal crack¢s depth of Longyangxia gravity arch dam was forecasted.

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SENSITIVITY ANALYSIS OF MESH SIZE ON CRACK TIP¢S
STRESS INTENSITY FACTOR

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2007, 26 (S2): -4147 doi:
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[PDF 256 KB] (735)

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Show Abstract

The stability of macrocrack in engineering was analyzed based on LEFM(linear elastic fracture mechanics) model；and the crack tip¢s stress intensity factor was calculated by displacement direct method. In response to the problems whether crack tip must be subdivided with fine-mesh and nodes¢ displacement were used to extrapolate the crack tip¢s stress intensity factor and so on，the sensitivity of mesh size on crack tip¢s stress intensity factor was analyzed. The following conclusion can be obtained. (1) When using displacement direct method to extrapolate the crack tip¢s stress intensity factor，it must ignore the nodal displacement near the crack tip and use the far field one；(2) If the 1/4 edge middle node(singular isoparametric element) was used near the crack tip，it could also obtain the satisfied result even with the coarse mesh，which will greatly reduce the computing workload. These findings were verified by the analyses of a typical three-point bent beam with cracks and the horizontal cracks of Longyangxia gravity arch dam. Then，base on LEFM model，the horizontal crack¢s depth of Longyangxia gravity arch dam was forecasted.

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RESEARCH ON STABILITY OF HYDROPOWER STATION PLUNGE POOL SLOPE AFFECTED BY ATOMIZATION-RAIN IN SOUTHWEST OF CHINA

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2007, 26 (S2): -4153 doi:
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[PDF 279 KB] (582)

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The plunge pool slope of a hydropower station in construction in Southwest of China is influenced by atomization-rain according to the forecast distribution of atomization-rain caused by spillway flood discharge. The slope is liable to fail in the form of horizontal-push landslide on the condition of rainfall based on the research of fissures combination and forces loaded on them. The block in the slope，which is made up of G222–2 as bottom slip face and f556–1 as back tension fracture，is liable to slide when the underground water level is 772.1 m high according to the calculating results of the start criterion of horizontal-push landslide. A seepage model of the underground water in the slope on raining condition is established to analyze the relationship between underground water level，and the time of raining for the underground water mainly comes from rainfall and atomization-rain. Results of calculating show that the start criterion is reached if there are rainstorm over 260 hours or both rainstorm and atomization-rain over 246 hours. And the horizontal-push landslide is to happen. In order to keep the slope safe，measures such as slope protection should be taken to isolate the rock from water.

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RESEARCH ON STABILITY OF HYDROPOWER STATION PLUNGE POOL SLOPE AFFECTED BY ATOMIZATION-RAIN IN SOUTHWEST OF CHINA

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2007, 26 (S2): -4153 doi:
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[PDF 279 KB] (650)

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The plunge pool slope of a hydropower station in construction in Southwest of China is influenced by atomization-rain according to the forecast distribution of atomization-rain caused by spillway flood discharge. The slope is liable to fail in the form of horizontal-push landslide on the condition of rainfall based on the research of fissures combination and forces loaded on them. The block in the slope，which is made up of G222–2 as bottom slip face and f556–1 as back tension fracture，is liable to slide when the underground water level is 772.1 m high according to the calculating results of the start criterion of horizontal-push landslide. A seepage model of the underground water in the slope on raining condition is established to analyze the relationship between underground water level，and the time of raining for the underground water mainly comes from rainfall and atomization-rain. Results of calculating show that the start criterion is reached if there are rainstorm over 260 hours or both rainstorm and atomization-rain over 246 hours. And the horizontal-push landslide is to happen. In order to keep the slope safe，measures such as slope protection should be taken to isolate the rock from water.

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STUDY ON PERMEABILITY OF JOINTED ROCK MASS AFTER
DYNAMIC UNLOADING OF INITIAL STRESS DURING
ROCK EXCAVATION

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2007, 26 (S2): -4158 doi:
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[PDF 204 KB] (689)

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The theory about stress wave and its propagation is employed to analyze the effect of dynamic unloading during excavation of jointed rock mass slope under high geostress. And the change rule of permeability of joints after loosing of unloading is discussed. The results demonstrate that a sudden unloading of high in-situ stress will make a remarkable loosing effect during excavation of jointed rock mass slope under high geostress，which should be considered. The factors，such as value of unloading during excavation，modulus of elasticity of rock mass，distribution of joints，etc.，will influence the permeability by the way of affecting the openings of joints. The interface between integrated bedrock and joined rock mass is always the obvious loosing position during excavation，which gets a prominent change of permeability coefficient. For the rock mass of vertical slope which is divided vertically by a set of parallel joints with equal spacing，if modulus of elasticity of rock blocks linearly increases from outside to inside，the results of calculation present a rule that the value of permeability coefficient decreases exponentially(from outside to inside)；while if modulus of elasticity is constant，there is no loosing effect of unloading during excavation.

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STUDY ON PERMEABILITY OF JOINTED ROCK MASS AFTER
DYNAMIC UNLOADING OF INITIAL STRESS DURING
ROCK EXCAVATION

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2007, 26 (S2): -4158 doi:
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[PDF 204 KB] (531)

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The theory about stress wave and its propagation is employed to analyze the effect of dynamic unloading during excavation of jointed rock mass slope under high geostress. And the change rule of permeability of joints after loosing of unloading is discussed. The results demonstrate that a sudden unloading of high in-situ stress will make a remarkable loosing effect during excavation of jointed rock mass slope under high geostress，which should be considered. The factors，such as value of unloading during excavation，modulus of elasticity of rock mass，distribution of joints，etc.，will influence the permeability by the way of affecting the openings of joints. The interface between integrated bedrock and joined rock mass is always the obvious loosing position during excavation，which gets a prominent change of permeability coefficient. For the rock mass of vertical slope which is divided vertically by a set of parallel joints with equal spacing，if modulus of elasticity of rock blocks linearly increases from outside to inside，the results of calculation present a rule that the value of permeability coefficient decreases exponentially(from outside to inside)；while if modulus of elasticity is constant，there is no loosing effect of unloading during excavation.

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THREE-DIMENSIONAL RELIABILITY ANALYSIS OF SOIL SLOPE BASED ON GA METHOD

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2007, 26 (S2): -4164 doi:
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[PDF 226 KB] (632)

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An assumption about the failure width of failing soil mass usually should be presented at first when slope stability is evaluated by three-dimensional factor of safety or three-dimensional reliability index. But，as a result of this assumption，the three-dimensional factor of safety or reliability index isn¢t the minimal one，which can not represent the real safety level of slope stability. Actually there should be three-dimensional critical slip surfaces which give the highest failure probability if spatial variabilities of soil parameters are taken into consideration. The minimal three-dimensional reliability index and the corresponding critical slip surface are investigated and illustrated. This makes it possible to get three-dimensional reliability index of soil slope by means of optimization techniques. Genetic algorithm(GA) is good for finding the global optimum solution of problem searching for the critical three-dimensional surface of soil slope. So，the model of spatial variabilities of soil parameters is adopted and the GA is used to search for the reliability index directly，then the three-dimensional reliability analysis method for slope stability，based on the GA，is proposed in combination with Bishop¢s simplified method. The minimal three-dimensional reliability index，which can represent the real safety level of slope stability，and the corresponding three-dimensional slip surface are achieved without assumptions about the width of failing soil mass. This method is proven to be efficient by the examples.

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THREE-DIMENSIONAL RELIABILITY ANALYSIS OF SOIL SLOPE BASED ON GA METHOD

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2007, 26 (S2): -4164 doi:
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[PDF 226 KB] (618)

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An assumption about the failure width of failing soil mass usually should be presented at first when slope stability is evaluated by three-dimensional factor of safety or three-dimensional reliability index. But，as a result of this assumption，the three-dimensional factor of safety or reliability index isn¢t the minimal one，which can not represent the real safety level of slope stability. Actually there should be three-dimensional critical slip surfaces which give the highest failure probability if spatial variabilities of soil parameters are taken into consideration. The minimal three-dimensional reliability index and the corresponding critical slip surface are investigated and illustrated. This makes it possible to get three-dimensional reliability index of soil slope by means of optimization techniques. Genetic algorithm(GA) is good for finding the global optimum solution of problem searching for the critical three-dimensional surface of soil slope. So，the model of spatial variabilities of soil parameters is adopted and the GA is used to search for the reliability index directly，then the three-dimensional reliability analysis method for slope stability，based on the GA，is proposed in combination with Bishop¢s simplified method. The minimal three-dimensional reliability index，which can represent the real safety level of slope stability，and the corresponding three-dimensional slip surface are achieved without assumptions about the width of failing soil mass. This method is proven to be efficient by the examples.

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2007, 26 (S2): -4170 doi:
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[PDF 222 KB] (638)

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Taking the strata of the area between Faults F3 and F4 in the Renlou Coal Mine as the prototype，the similar material model is constructed. The mining effect of the rock mass at fault zone and the possibility of water-inrush from the aquifer of footwall of fault are simulated. The results show that，with reducing the coal pillar，there are differences between the deformation of rock mass of two walls of the fault，and the characteristics of mining effect are different. And when the coal pillar is reduced to a certain value，there is relative movement between the hanging and the foot wall rock mass of the fault and the fault becomes active resulting in water-conducting along the fault. Meanwhile，the confined aquifer influences the mining effect in the fault and promotes the fault to become active. Therefore，in the process of the establishment of water-preventing coal pillar in the fault，the factors must be considered to provide reliable protection for the safe and efficient production of coal mine.

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2007, 26 (S2): -4170 doi:
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[PDF 222 KB] (910)

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Taking the strata of the area between Faults F3 and F4 in the Renlou Coal Mine as the prototype，the similar material model is constructed. The mining effect of the rock mass at fault zone and the possibility of water-inrush from the aquifer of footwall of fault are simulated. The results show that，with reducing the coal pillar，there are differences between the deformation of rock mass of two walls of the fault，and the characteristics of mining effect are different. And when the coal pillar is reduced to a certain value，there is relative movement between the hanging and the foot wall rock mass of the fault and the fault becomes active resulting in water-conducting along the fault. Meanwhile，the confined aquifer influences the mining effect in the fault and promotes the fault to become active. Therefore，in the process of the establishment of water-preventing coal pillar in the fault，the factors must be considered to provide reliable protection for the safe and efficient production of coal mine.

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STUDY ON 3D ENGINEERING GEOLOGY MODELING AND ANALYSIS SYSTEM DESIGN

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2007, 26 (S2): -4176 doi:
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[PDF 449 KB] (607)

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A 3D engineering geology modelling and analysis system is designed based on the complex data structure of boundary representation(Brep) and TIN，as well as the GIS technique. The TIN model is used to fit the stratum interfaces. A few methods to build TIN model are supposed，such as the discrete points converting from the contour line and the DEM model. The techniques of intersection，cutting and mending between the TIN model are also discussed. The geological information can be realistically represented by color and texture mapping. Furthermore，the analysis method based on the 3D geological model is presented，including generation of geological section，calculating area and volume of the stratum body. Finally，the 3D engineering geology modelling and analysis system is applied to simulate some projects，such as the coast，slope，hydraulic and hydroelectric project，and excavated highway slope. The results show that the theories and system have favourable reliability and practicability.

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STUDY ON 3D ENGINEERING GEOLOGY MODELING AND ANALYSIS SYSTEM DESIGN

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2007, 26 (S2): -4176 doi:
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[PDF 449 KB] (874)

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A 3D engineering geology modelling and analysis system is designed based on the complex data structure of boundary representation(Brep) and TIN，as well as the GIS technique. The TIN model is used to fit the stratum interfaces. A few methods to build TIN model are supposed，such as the discrete points converting from the contour line and the DEM model. The techniques of intersection，cutting and mending between the TIN model are also discussed. The geological information can be realistically represented by color and texture mapping. Furthermore，the analysis method based on the 3D geological model is presented，including generation of geological section，calculating area and volume of the stratum body. Finally，the 3D engineering geology modelling and analysis system is applied to simulate some projects，such as the coast，slope，hydraulic and hydroelectric project，and excavated highway slope. The results show that the theories and system have favourable reliability and practicability.

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COMPARISON OF INFRARED RADIATIONS OF BRITTLE ROCK AND POLYMETHYL MECHACRYLATE INDUCED BY STRESS

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2007, 26 (S2): -4183 doi:
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[PDF 297 KB] (592)

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The studies on remote sensing rock mechanics(RSRM) in recent years show that rock has regular features of infrared radiation(IR) when the rock is loaded，and the anomalous IR phenomena appear before rock fracture. In order to understand the IR feature of loaded rock and its physical mechanism，the IR features of rock under uniaxial compression are compared with those of polymethyl mechacrylate(PMMA) under similar conditions. The results show that：(1) during the whole loading process，the radiation intensity of PMMA increases symmetrically and no local anomaly appears in the thermal image，but the anomalous radiation appears frequently in the thermal image of rock before fracture，and it appears in strips and the location of strips corresponds to those of rock fractures；and (2) different stress stages show different IR features，but the IR patterns of two materials are different. The average IR radiation temperature(AIRT) of PMMA rises in the form of sectional line with the variation of stress state. However，AIRT variation curve of rock with time presents diverse forms，and the anomalous AIRT precursors appear before rock fracture. The mechanism of thermomechanical coupling is discussed and the result shows that the thermomechanical coupling effects of rock include thermoelastic effect，endothermic effect caused by gas escaping，and friction heat effect due to generation of a mass of cracks. Comparatively，PMMA has thermoelastic effect，thermoplastic and thermoviscous effects. The difference of thermomechanical coupling effect is the cause to result in IR feature difference between rock and PMMA.

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COMPARISON OF INFRARED RADIATIONS OF BRITTLE ROCK AND POLYMETHYL MECHACRYLATE INDUCED BY STRESS

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2007, 26 (S2): -4183 doi:
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[PDF 297 KB] (567)

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The studies on remote sensing rock mechanics(RSRM) in recent years show that rock has regular features of infrared radiation(IR) when the rock is loaded，and the anomalous IR phenomena appear before rock fracture. In order to understand the IR feature of loaded rock and its physical mechanism，the IR features of rock under uniaxial compression are compared with those of polymethyl mechacrylate(PMMA) under similar conditions. The results show that：(1) during the whole loading process，the radiation intensity of PMMA increases symmetrically and no local anomaly appears in the thermal image，but the anomalous radiation appears frequently in the thermal image of rock before fracture，and it appears in strips and the location of strips corresponds to those of rock fractures；and (2) different stress stages show different IR features，but the IR patterns of two materials are different. The average IR radiation temperature(AIRT) of PMMA rises in the form of sectional line with the variation of stress state. However，AIRT variation curve of rock with time presents diverse forms，and the anomalous AIRT precursors appear before rock fracture. The mechanism of thermomechanical coupling is discussed and the result shows that the thermomechanical coupling effects of rock include thermoelastic effect，endothermic effect caused by gas escaping，and friction heat effect due to generation of a mass of cracks. Comparatively，PMMA has thermoelastic effect，thermoplastic and thermoviscous effects. The difference of thermomechanical coupling effect is the cause to result in IR feature difference between rock and PMMA.

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STABILITY ANALYSIS AND SUPPORTING SELECTION OF MULTI-LAYER COMPLEX LANDSLIDE

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2007, 26 (S2): -4189 doi:
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[PDF 206 KB] (603)

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There are some complicated landslides with several layers of slipping plane in the geotechnical engineering. Because of the alteration of engineering slope and the action of engineering structure，the slope structure and stress state will be changed. The original slide surface is not the most critical one，but the new critical slide surface will form based on it. Now little attention is paid to it. In this paper，a stability calculation method with the specified shear-out point is proposed，and a new search procedure is adopted to calculate factor of safety of each point on the slope surface. This method assumes that the most critical slide surfaces after construction is the combined sliding surfaces of the new and the original. Based on the method，the stability analysis is conducted for the multi-layer complex landslide. And the result is adopted to design supporting structure form and to determine the appropriate supporting position. Taking a practical engineering slope as an example，the application procedure of this method is described in details；and the design principle of supporting for large scale slide is suggested. The research result is meaningful for supporting design of complicated landslide.

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STABILITY ANALYSIS AND SUPPORTING SELECTION OF MULTI-LAYER COMPLEX LANDSLIDE

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2007, 26 (S2): -4189 doi:
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[PDF 206 KB] (680)

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There are some complicated landslides with several layers of slipping plane in the geotechnical engineering. Because of the alteration of engineering slope and the action of engineering structure，the slope structure and stress state will be changed. The original slide surface is not the most critical one，but the new critical slide surface will form based on it. Now little attention is paid to it. In this paper，a stability calculation method with the specified shear-out point is proposed，and a new search procedure is adopted to calculate factor of safety of each point on the slope surface. This method assumes that the most critical slide surfaces after construction is the combined sliding surfaces of the new and the original. Based on the method，the stability analysis is conducted for the multi-layer complex landslide. And the result is adopted to design supporting structure form and to determine the appropriate supporting position. Taking a practical engineering slope as an example，the application procedure of this method is described in details；and the design principle of supporting for large scale slide is suggested. The research result is meaningful for supporting design of complicated landslide.

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RESEARCH ON DISCONTINUOUS DEFORMATION ANALYSIS COUPLED WITH MESHFREE METHODS

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2007, 26 (S2): -4195 doi:
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[PDF 379 KB] (659)

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The linear displacement function of discontinuous deformation analysis(DDA) is a complete first-order polynomial，which can only describe block element with constant strain，and in practice，it cannot provide required precision and sometimes will cause large errors. Recently，some improvements are developed such as the direct usage of the displacement function with higher-order polynomials，sub-blocks with additional artificial joint sets along the border，and the block-finite-element displacement mode，etc.. However，all these have their own defects. As the meshfree methods have many efficient interpolation modes，the moving least squares(MLS) procedure commonly adopted in the element free Galerkin(EFG) method can be used to describe displacement and stress field. Hence，new interpolation nodes are inserted into the blocks and their borders，and any point in a block has a new displacement expression by MLS interpolation of nodal displacements of the block，and the basic procedures of the original DDA are presented including building the simultaneous equilibrium equations according to energy extremum theory，implicitly solving unknown variables，using time-step iteration procedures to solve uniformly dynamic or static problems and open-close iteration procedure to search for possible contact types，etc.. The numerical examples indicate that the proposed scheme can efficiently simulate block stress field；and the results are obviously better than those of linear mode DDA.

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RESEARCH ON DISCONTINUOUS DEFORMATION ANALYSIS COUPLED WITH MESHFREE METHODS

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2007, 26 (S2): -4195 doi:
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[PDF 379 KB] (450)

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The linear displacement function of discontinuous deformation analysis(DDA) is a complete first-order polynomial，which can only describe block element with constant strain，and in practice，it cannot provide required precision and sometimes will cause large errors. Recently，some improvements are developed such as the direct usage of the displacement function with higher-order polynomials，sub-blocks with additional artificial joint sets along the border，and the block-finite-element displacement mode，etc.. However，all these have their own defects. As the meshfree methods have many efficient interpolation modes，the moving least squares(MLS) procedure commonly adopted in the element free Galerkin(EFG) method can be used to describe displacement and stress field. Hence，new interpolation nodes are inserted into the blocks and their borders，and any point in a block has a new displacement expression by MLS interpolation of nodal displacements of the block，and the basic procedures of the original DDA are presented including building the simultaneous equilibrium equations according to energy extremum theory，implicitly solving unknown variables，using time-step iteration procedures to solve uniformly dynamic or static problems and open-close iteration procedure to search for possible contact types，etc.. The numerical examples indicate that the proposed scheme can efficiently simulate block stress field；and the results are obviously better than those of linear mode DDA.

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RESEARCH ON NUMERICAL SIMULATION OF NATURAL CAVING METHOD BASED ON PARTICLE FLOW METHOD

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2007, 26 (S2): -4202 doi:
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[PDF 519 KB] (994)

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Numerical simulation of natural caving is conducted from meso-mechanics view through particle on the basis of method(PFM). A method is proposed to calibrate the parameters for the meso-mechanical model from meso-mechanics. The technique for initial stress field is also recommended. The proposed scheme has been applied to study the rupture evolution and contact force distribution after caving process at a mine in China. It will be helpful for research on caving in view of micro-mechanics.

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RESEARCH ON NUMERICAL SIMULATION OF NATURAL CAVING METHOD BASED ON PARTICLE FLOW METHOD

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2007, 26 (S2): -4202 doi:
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[PDF 519 KB] (937)

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KEY TECHNIQUES ON SHALLOW EMBEDDED TUNNEL CONSTRUCTED BENEATH EXISTING SUBWAY TUNNEL

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2007, 26 (S2): -4208 doi:
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[PDF 295 KB] (802)

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With respect to more and more shallow embedded tunnel constructed beneath existing subway tunnel，the effects of shallow embedded tunnel construction on existing subway tunnel are discussed；and some key control techniques used successfully in Chongwenmen station of Beijing metro line No.5 constructed beneath existing tunnel of metro line No.2 are presented. A comprehensive survey of the existing subway tunnel has been performed before the tunnel construction. Based on the survey results，the deformation control indexes and their allowable values are identified in the light of theoretical analyses and similar engineer experiences. The finite element method combined with experience and judgment is recommended to predict the effects of tunneling on the existing subway. The more suitable excavation construction methods and auxiliary measures such as big steel pipes，face grouting reinforcement and compensation grouting are selected by various comparison analyses. On the basis of numerical analyses and similar engineer experiences，the allowable value of the main deformation control index is controlled according to construction steps. A system of remote real-time monitoring is used to monitor dynamic responses of the existing subway；and the measured data were back analyzed immediately. When abnormal issues are found，protective measures are adopted in time to ensure safety running of the existing subway. For example，control compaction grouting is adopted to heave up the existing tunnel structures in the case，and the maximum upheaval of the existing tunnel reaches 16 mm.

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KEY TECHNIQUES ON SHALLOW EMBEDDED TUNNEL CONSTRUCTED BENEATH EXISTING SUBWAY TUNNEL

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2007, 26 (S2): -4208 doi:
Full Text:

[PDF 295 KB] (748)

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With respect to more and more shallow embedded tunnel constructed beneath existing subway tunnel，the effects of shallow embedded tunnel construction on existing subway tunnel are discussed；and some key control techniques used successfully in Chongwenmen station of Beijing metro line No.5 constructed beneath existing tunnel of metro line No.2 are presented. A comprehensive survey of the existing subway tunnel has been performed before the tunnel construction. Based on the survey results，the deformation control indexes and their allowable values are identified in the light of theoretical analyses and similar engineer experiences. The finite element method combined with experience and judgment is recommended to predict the effects of tunneling on the existing subway. The more suitable excavation construction methods and auxiliary measures such as big steel pipes，face grouting reinforcement and compensation grouting are selected by various comparison analyses. On the basis of numerical analyses and similar engineer experiences，the allowable value of the main deformation control index is controlled according to construction steps. A system of remote real-time monitoring is used to monitor dynamic responses of the existing subway；and the measured data were back analyzed immediately. When abnormal issues are found，protective measures are adopted in time to ensure safety running of the existing subway. For example，control compaction grouting is adopted to heave up the existing tunnel structures in the case，and the maximum upheaval of the existing tunnel reaches 16 mm.

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THEORETICAL MODEL ANALYSIS OF COMBINED VOUSSOIR
BEAMS EFFECT OF BOLT SUPPORTING IN
STRATIFIED ROCK ROOF

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2007, 26 (S2): -4215 doi:
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[PDF 190 KB] (433)

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The distinct element method，physical simulation and theoretical analysis have made it clear that the bolted stratified rock roof forms combined voussoir beams. The combined voussoir beams effect is one of the working mechanics of the rock bolting. Based on this theory，the average stress formula of the combined voussoir beams is derived. This formula can reflect the influencing factors on the stability of rock roof synthetically，such as the thickness of combined voussoir beams，the span of roadway，the thickness of single rock stratum，and the integrated coefficient of rock. The influencing regularity is discussed and the results complies with the practice.

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THEORETICAL MODEL ANALYSIS OF COMBINED VOUSSOIR
BEAMS EFFECT OF BOLT SUPPORTING IN
STRATIFIED ROCK ROOF

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2007, 26 (S2): -4215 doi:
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[PDF 190 KB] (641)

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The distinct element method，physical simulation and theoretical analysis have made it clear that the bolted stratified rock roof forms combined voussoir beams. The combined voussoir beams effect is one of the working mechanics of the rock bolting. Based on this theory，the average stress formula of the combined voussoir beams is derived. This formula can reflect the influencing factors on the stability of rock roof synthetically，such as the thickness of combined voussoir beams，the span of roadway，the thickness of single rock stratum，and the integrated coefficient of rock. The influencing regularity is discussed and the results complies with the practice.

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NUMERICAL SIMULATION AND MECHANICAL ANALYSIS OF END-ANCHORED BOLTS

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2007, 26 (S2): -4221 doi:
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[PDF 204 KB] (503)

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Combined with the 3D FEM，the end-anchored bolts are simulated by implicit bolt element. The stiffness contribution of bolt and prestress is deduced，and the strength of anchor end is also simulated. The implicit bolt elements are combined in the elements of rock mass，so the mesh generation is extremely simplified. However，the calculated stress of bolt is always greater than the measured value. This paper analyzes the interaction of rock bolt and rock mass，and presents the analytical expression of elastoplastic deformation of rock mass and bolt stress. The results indicate that it is essential to revise the bolt stress by using the formulas when rock mass is in plastic state. Finally，a case study indicates that the implicit bolt element can simulate well the supporting effect. And the calculated results agree with the observed ones. This paper offers some beneficial methods for more accurately simulating the support effect of bolts.

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NUMERICAL SIMULATION AND MECHANICAL ANALYSIS OF END-ANCHORED BOLTS

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2007, 26 (S2): -4221 doi:
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[PDF 204 KB] (685)

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Combined with the 3D FEM，the end-anchored bolts are simulated by implicit bolt element. The stiffness contribution of bolt and prestress is deduced，and the strength of anchor end is also simulated. The implicit bolt elements are combined in the elements of rock mass，so the mesh generation is extremely simplified. However，the calculated stress of bolt is always greater than the measured value. This paper analyzes the interaction of rock bolt and rock mass，and presents the analytical expression of elastoplastic deformation of rock mass and bolt stress. The results indicate that it is essential to revise the bolt stress by using the formulas when rock mass is in plastic state. Finally，a case study indicates that the implicit bolt element can simulate well the supporting effect. And the calculated results agree with the observed ones. This paper offers some beneficial methods for more accurately simulating the support effect of bolts.

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EXPERIMENTAL STUDY ON MECHANICAL PROPERTIES OF DENSE SANDSTONE UNDER DIFFERENT CONFINING PRESSURES

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2007, 26 (S2): -4227 doi:
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[PDF 195 KB] (708)

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The study of mechanical properties under changing effective stress is very important for gas reservoirs efficient development，but perfect experimental method and result are still not available. In order to get the mechanical characteristic of deuse-sandstone with the increasing of effective stress in gas reservoir development，the triaxial compression deformation experiment is performed on the GCTS–RTR–1000 triaxial rock testing system. Testing result shows that both the value of deformation modulus and Poisson¢s ratio increase with the increase of confining pressure. By comparing with the conventional experiment with constant confining pressure，the value of deformation modulus is higher than that of the constant confining pressure，while the value of Poisson¢s ratio under the condition of increasing confining pressure gets smaller.

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EXPERIMENTAL STUDY ON MECHANICAL PROPERTIES OF DENSE SANDSTONE UNDER DIFFERENT CONFINING PRESSURES

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2007, 26 (S2): -4227 doi:
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[PDF 195 KB] (642)

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The study of mechanical properties under changing effective stress is very important for gas reservoirs efficient development，but perfect experimental method and result are still not available. In order to get the mechanical characteristic of deuse-sandstone with the increasing of effective stress in gas reservoir development，the triaxial compression deformation experiment is performed on the GCTS–RTR–1000 triaxial rock testing system. Testing result shows that both the value of deformation modulus and Poisson¢s ratio increase with the increase of confining pressure. By comparing with the conventional experiment with constant confining pressure，the value of deformation modulus is higher than that of the constant confining pressure，while the value of Poisson¢s ratio under the condition of increasing confining pressure gets smaller.

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DYNAMIC STABILITY ANALYSIS OF ARCH DAM ABUTMENT
WITH DISCONTINUOUS MEDIA MODEL

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2007, 26 (S2): -4232 doi:
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[PDF 268 KB] (544)

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There are many faults and cracks in rock of arch dam abutment. It is appropriate that abutment stability is analyzed by discontinuous media mechanical model. The interface element method(IEM) is well used in the modelling of the displacement discontinuity in the interface of two adjacent elements. It is applicable to describe the phenomena of detachment and sliding between the two elements. The more practicable results may be obtained with the IEM being used to analyze the abutment stability. The concerned variables，such as water pressure，earthquake load，material parameters and so on，are random variables in the study of abutment stability. Structural reliability theory is suitable for the analysis of abutment stability. The abutment rock mass is deformable body，and the stress and deformation of the abutment rock mass are the main indexes in determining the abutment stability. The tensile and shearing strength of faults and interfaces are regarded as the criterion to establish the limit state equation. The response surface method is used in the reliability analysis of abutment. In order to calculate the system reliability of abutment，the stiffness matrix must be modified continuously to analyze the change of the structure. The method is used in an example of reliability analysis of abutment stability，and the obtained result shows that it is suitable for the stability analysis of abutment.

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DYNAMIC STABILITY ANALYSIS OF ARCH DAM ABUTMENT
WITH DISCONTINUOUS MEDIA MODEL

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2007, 26 (S2): -4232 doi:
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[PDF 268 KB] (686)

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There are many faults and cracks in rock of arch dam abutment. It is appropriate that abutment stability is analyzed by discontinuous media mechanical model. The interface element method(IEM) is well used in the modelling of the displacement discontinuity in the interface of two adjacent elements. It is applicable to describe the phenomena of detachment and sliding between the two elements. The more practicable results may be obtained with the IEM being used to analyze the abutment stability. The concerned variables，such as water pressure，earthquake load，material parameters and so on，are random variables in the study of abutment stability. Structural reliability theory is suitable for the analysis of abutment stability. The abutment rock mass is deformable body，and the stress and deformation of the abutment rock mass are the main indexes in determining the abutment stability. The tensile and shearing strength of faults and interfaces are regarded as the criterion to establish the limit state equation. The response surface method is used in the reliability analysis of abutment. In order to calculate the system reliability of abutment，the stiffness matrix must be modified continuously to analyze the change of the structure. The method is used in an example of reliability analysis of abutment stability，and the obtained result shows that it is suitable for the stability analysis of abutment.

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VARIATION CHARACTERISTICS OF ANCHOR CABLE PRESTRESS DURING UNDERGROUND OPENING EXCAVATION
AND OVERLOADING

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2007, 26 (S2): -4238 doi:
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[PDF 290 KB] (655)

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By geomechanical model tests，the variation characteristics of tension in non-bonded prestressed anchor cable and fully grouted anchor cable during the underground opening excavation and overloading are given. Based on the analysis of the developed charts of the variation of tension in cables，it is found that the tension in the two types of cables generally decreases and the average range is 15%–22% during the underground opening excavation. The variation magnitude of tension decreases and the corresponding position of each anchor cable in different places obviously show randomness. In overloading process of the model test，the tension generally increases and the position where the tension increases is relevant to the coefficient of horizontal pressure of the model. The tension in anchor cables installed in the arch ends increases more and that in anchor cables installed in the arch crown and the floor increases less when the coefficient of horizontal pressure is less than 1(N＜1 . Whether the tension in anchor cables decreases during the opening excavation or increases during the opening overloading，the relative increment of tension is more for anchor cables with low initial tension，otherwise，the relative increment of tension is less. Consequently，the different ratio of tension in anchor cables should be taken for anchor cables with different initial tension load. A low ratio should be taken for anchor cables with high initial tension and a high ratio should be taken for anchor cables with low initial tension load. Several suggestions are provided for the design and field construction of anchor cable.

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VARIATION CHARACTERISTICS OF ANCHOR CABLE PRESTRESS DURING UNDERGROUND OPENING EXCAVATION
AND OVERLOADING

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2007, 26 (S2): -4238 doi:
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[PDF 290 KB] (510)

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By geomechanical model tests，the variation characteristics of tension in non-bonded prestressed anchor cable and fully grouted anchor cable during the underground opening excavation and overloading are given. Based on the analysis of the developed charts of the variation of tension in cables，it is found that the tension in the two types of cables generally decreases and the average range is 15%–22% during the underground opening excavation. The variation magnitude of tension decreases and the corresponding position of each anchor cable in different places obviously show randomness. In overloading process of the model test，the tension generally increases and the position where the tension increases is relevant to the coefficient of horizontal pressure of the model. The tension in anchor cables installed in the arch ends increases more and that in anchor cables installed in the arch crown and the floor increases less when the coefficient of horizontal pressure is less than 1(N＜1 . Whether the tension in anchor cables decreases during the opening excavation or increases during the opening overloading，the relative increment of tension is more for anchor cables with low initial tension，otherwise，the relative increment of tension is less. Consequently，the different ratio of tension in anchor cables should be taken for anchor cables with different initial tension load. A low ratio should be taken for anchor cables with high initial tension and a high ratio should be taken for anchor cables with low initial tension load. Several suggestions are provided for the design and field construction of anchor cable.

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NUMERICAL SIMULATION OF CONSTRUCTION PROCESS OF ROCK MASS OF AN UNDERGROUND STORAGE AND INTERACTION OF ROCK-CASING

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2007, 26 (S2): -4245 doi:
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[PDF 386 KB] (352)

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With finite element software ABAQUS，a three-dimensional viscoelasto-plastic finite element analysis was performed for the excavation of rock mass of a natural gas underground storage. The stress variation and deformation during the excavation process were calculated and analyzed. The deformation of the casing with which water is pumped in and out was calculated. The main researchs include：(1) the stress field and displacement distribution of rockmass caused by solution mining were presented，as well as a curve of rock mass displacement versus z-direction for the rock around casing；(2) a practical curve of viscoplastic constitutive model of rock mass with reference to the form requirements of software ABAQUS was given out；(3) the possible plastic area was predicted，and the estimation of the stability of the storage rock mass structure was given out. The numerical results indicate that the self-bearing system which is characterized by “compressive arch” has been formed around the storage space after 3 years solution mining construction. The design of the underground storage is reasonable and practical. However，it is necessary to adopt reasonable measure to enhance the lower section of casing as well as to reduce the pulling effect of rock mass acting on the casing.

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NUMERICAL SIMULATION OF CONSTRUCTION PROCESS OF ROCK MASS OF AN UNDERGROUND STORAGE AND INTERACTION OF ROCK-CASING

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2007, 26 (S2): -4245 doi:
Full Text:

[PDF 386 KB] (1625)

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With finite element software ABAQUS，a three-dimensional viscoelasto-plastic finite element analysis was performed for the excavation of rock mass of a natural gas underground storage. The stress variation and deformation during the excavation process were calculated and analyzed. The deformation of the casing with which water is pumped in and out was calculated. The main researchs include：(1) the stress field and displacement distribution of rockmass caused by solution mining were presented，as well as a curve of rock mass displacement versus z-direction for the rock around casing；(2) a practical curve of viscoplastic constitutive model of rock mass with reference to the form requirements of software ABAQUS was given out；(3) the possible plastic area was predicted，and the estimation of the stability of the storage rock mass structure was given out. The numerical results indicate that the self-bearing system which is characterized by “compressive arch” has been formed around the storage space after 3 years solution mining construction. The design of the underground storage is reasonable and practical. However，it is necessary to adopt reasonable measure to enhance the lower section of casing as well as to reduce the pulling effect of rock mass acting on the casing.

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STUDY ON OPTIMIZATION DESIGN OF PILE BEARING LAYER ACCORDING TO CONTRASTIVE TESTS WITH DIFFERENT PILE LENGTHS

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2007, 26 (S2): -4251 doi:
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[PDF 220 KB] (499)

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The behaviors of bearing capacity and settlement of bored piles in two different depth bearing layers with/without end post-grouting are studied contrastively through static load tests for piles with different lengths in a certain engineering practice of Ningbo City. The study results show that if the 8th soil stratum—silty soil is selected as bearing layer，the pile length is 55 m and employing pile end post-grouting can increase the bearing capability and decrease the pile top settlement remarkably；although selecting the 13th soil stratum—sandy gravel embedded with clay as bearing layer，where there is bedrock below，it can prevent pile end from plunge failure effectively. Therefore the pile length is 88 m and it is very difficult to penetrate the silty sand stratum during installation，which is about 20 m in thickness. Therefore，the construction quality is hard to control. This makes mudcakes around piles at pile ends too thick，resulting in decreasing of the bearing capability of single pile and failure to meet design requirements. The technical economic analysis is made quantitatively and the selection of pile bearing layer is optimized. In order to guarantee the safety of engineering piles，it should reduce the cost as minimum as possible and make pile installation convenient. The silt soil stratum is finally selected as the bearing layer.

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STUDY ON OPTIMIZATION DESIGN OF PILE BEARING LAYER ACCORDING TO CONTRASTIVE TESTS WITH DIFFERENT PILE LENGTHS

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2007, 26 (S2): -4251 doi:
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[PDF 220 KB] (859)

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The behaviors of bearing capacity and settlement of bored piles in two different depth bearing layers with/without end post-grouting are studied contrastively through static load tests for piles with different lengths in a certain engineering practice of Ningbo City. The study results show that if the 8th soil stratum—silty soil is selected as bearing layer，the pile length is 55 m and employing pile end post-grouting can increase the bearing capability and decrease the pile top settlement remarkably；although selecting the 13th soil stratum—sandy gravel embedded with clay as bearing layer，where there is bedrock below，it can prevent pile end from plunge failure effectively. Therefore the pile length is 88 m and it is very difficult to penetrate the silty sand stratum during installation，which is about 20 m in thickness. Therefore，the construction quality is hard to control. This makes mudcakes around piles at pile ends too thick，resulting in decreasing of the bearing capability of single pile and failure to meet design requirements. The technical economic analysis is made quantitatively and the selection of pile bearing layer is optimized. In order to guarantee the safety of engineering piles，it should reduce the cost as minimum as possible and make pile installation convenient. The silt soil stratum is finally selected as the bearing layer.

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STUDY ON UNLOADING REBOUND DEFORMATION OF DREDGER FILL WITH CENTRIFUGE MODELING TEST

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2007, 26 (S2): -4258 doi:
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[PDF 219 KB] (626)

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Dredger fill is characterized with unloading deformation. Unloading deformation of dredger fill is studied with a centrifuge model test. The test results show that the curve of average deformation vs. load is linear；the curve of average deformation and loading-time is hyperbola，and there are two critical unloading ratios in unloading deformation，which is 0.4 and 0.9 respectively. When the critical unloading ratio is less than 0.4，the increment of pore ratio is very slow，and the pore ratio increases with increasing of unloading ratio. When the critical unloading ratio reaches 0.6，the pore ratio linearly increases with increasing of unloading ratio. However，when the critical unloading ratio reaches 0.9，the pore ratio does not increase with the increase of unloading ratio. An empirical formulation is determined through fitting to describe the relationship between pore ratio and unloading ratio. The formula can be used to predict the unloading deformation of dredger fill.

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STUDY ON UNLOADING REBOUND DEFORMATION OF DREDGER FILL WITH CENTRIFUGE MODELING TEST

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2007, 26 (S2): -4258 doi:
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[PDF 219 KB] (624)

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Dredger fill is characterized with unloading deformation. Unloading deformation of dredger fill is studied with a centrifuge model test. The test results show that the curve of average deformation vs. load is linear；the curve of average deformation and loading-time is hyperbola，and there are two critical unloading ratios in unloading deformation，which is 0.4 and 0.9 respectively. When the critical unloading ratio is less than 0.4，the increment of pore ratio is very slow，and the pore ratio increases with increasing of unloading ratio. When the critical unloading ratio reaches 0.6，the pore ratio linearly increases with increasing of unloading ratio. However，when the critical unloading ratio reaches 0.9，the pore ratio does not increase with the increase of unloading ratio. An empirical formulation is determined through fitting to describe the relationship between pore ratio and unloading ratio. The formula can be used to predict the unloading deformation of dredger fill.

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EXPERIMENTAL STUDY ON SHIFT-BORING LINING OF HIGH PERFORMANCE CONCRETE AND DOUBLE STEEL CYLINDER IN SUPER-DEEP ALLUVIUM

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2007, 26 (S2): -4264 doi:
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[PDF 309 KB] (528)

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Aiming at the supporting problem of the shaft-boring in the deep alluvium of 500–700 m，the composite shaft lining of high strength and high performance concrete and double steel cylinder is presented. Firstly，the optimized mixture ratio of the shaft-boring lining C60–C75 high strength and high performance concrete is given. Then，according to similarity theory，the model design of the composite shaft lining of high and strength high performance concrete and double steel cylinder is done. Through model experiments，the characteristics of stress and strength of the composite shaft lining of and high strength high performance concrete and double steel cylinder are studied. The results indicate that the concrete bearing strength increases greatly under triaxial compressive stresses states between inner and outer steel plate cylinders. The concrete utmost compressive strain achieves －4 600 me and the shaft lining is fairly ductility when it is damaged. Thus，the results can provide a design basis for engineering practice of this shaft lining structure. Now the study results have been applied to three shaft-borings in the alluvium.

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EXPERIMENTAL STUDY ON SHIFT-BORING LINING OF HIGH PERFORMANCE CONCRETE AND DOUBLE STEEL CYLINDER IN SUPER-DEEP ALLUVIUM

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2007, 26 (S2): -4264 doi:
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[PDF 309 KB] (458)

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Aiming at the supporting problem of the shaft-boring in the deep alluvium of 500–700 m，the composite shaft lining of high strength and high performance concrete and double steel cylinder is presented. Firstly，the optimized mixture ratio of the shaft-boring lining C60–C75 high strength and high performance concrete is given. Then，according to similarity theory，the model design of the composite shaft lining of high and strength high performance concrete and double steel cylinder is done. Through model experiments，the characteristics of stress and strength of the composite shaft lining of and high strength high performance concrete and double steel cylinder are studied. The results indicate that the concrete bearing strength increases greatly under triaxial compressive stresses states between inner and outer steel plate cylinders. The concrete utmost compressive strain achieves －4 600 me and the shaft lining is fairly ductility when it is damaged. Thus，the results can provide a design basis for engineering practice of this shaft lining structure. Now the study results have been applied to three shaft-borings in the alluvium.

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DYNAMIC RESPONSES OF INFINITE PLATE ON LAYERED PORO-ELASTIC SUBSOILS SUBJECTED TO MOVING LOADS

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2007, 26 (S2): -4270 doi:
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[PDF 410 KB] (640)

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Based on the Biot¢s dynamic equation and the theory of elastic plate，the dynamic responses of an infinite plate on a layered poro-elastic subsoils subjected to moving loads is studied by the transmission and reflection matrices(TRM) method. Numerical results of bending moment and shear force for the plate are obtained by performing inverse Fourier transformation in the time-space domain. Moreover，the vibration of subsoil due to the moving load is also retrieved. The present methodology is validated by comparing the solutions with some monitoring results. Two examples and the corresponding analysis are presented. Based on the analysis，it can be seen that the occurrence of a softer middle layer inside the layered subsoil will enhance the internal force of beam and the pore pressure considerably. It also indicates that the dynamic response becomes more oscillatory and concentrated to the region of load with increasing the moving load velocity.

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DYNAMIC RESPONSES OF INFINITE PLATE ON LAYERED PORO-ELASTIC SUBSOILS SUBJECTED TO MOVING LOADS

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2007, 26 (S2): -4270 doi:
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[PDF 410 KB] (644)

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Based on the Biot¢s dynamic equation and the theory of elastic plate，the dynamic responses of an infinite plate on a layered poro-elastic subsoils subjected to moving loads is studied by the transmission and reflection matrices(TRM) method. Numerical results of bending moment and shear force for the plate are obtained by performing inverse Fourier transformation in the time-space domain. Moreover，the vibration of subsoil due to the moving load is also retrieved. The present methodology is validated by comparing the solutions with some monitoring results. Two examples and the corresponding analysis are presented. Based on the analysis，it can be seen that the occurrence of a softer middle layer inside the layered subsoil will enhance the internal force of beam and the pore pressure considerably. It also indicates that the dynamic response becomes more oscillatory and concentrated to the region of load with increasing the moving load velocity.

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EXPERIMENTAL STUDY ON DYNAMIC STRENGTH PROPERTIES OF LIGHTWEIGHT CLAY MIXED WITH EPS BEADS SOIL

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2007, 26 (S2): -4276 doi:
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[PDF 304 KB] (353)

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A series of laboratory dynamic triaxial tests are carried out to study the dynamic strength properties of lightweight clay mixed with expanded polystyrene beads soil(LCES). Firstly，the material will be in failure when the compressive strain reaches 5%，which can be considered to be a suitable dynamic failure criterion of LCES，and then the effort is focused on the confining pressure，cement content and EPS content effect on the dynamic strength properties of LCES. The test results indicate that the dynamic strength of LCES increases with the increasing confining pressure and cement content，however，the effect of confining pressure on the dynamic strength declines when the cement content increases. The dynamic strength of LCES initially increases and then decreases with the increase of EPS content，so LCES may has an optimal EPS content for the dynamic strength. Cement and EPS have considerable effects on the increase of the dynamic strength paramete of LCES，but they have few effects on the increase of the parameter jd. The relationship of dynamic shear strength and cyclic number(td-Nf) can be simulated by the power function properly. By considering synthetically the influences of confining pressure，cement content and EPS content，dynamic shear strength curves of LCES are normalized，and the dynamic strength formula is obtained.

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EXPERIMENTAL STUDY ON DYNAMIC STRENGTH PROPERTIES OF LIGHTWEIGHT CLAY MIXED WITH EPS BEADS SOIL

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2007, 26 (S2): -4276 doi:
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[PDF 304 KB] (742)

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A series of laboratory dynamic triaxial tests are carried out to study the dynamic strength properties of lightweight clay mixed with expanded polystyrene beads soil(LCES). Firstly，the material will be in failure when the compressive strain reaches 5%，which can be considered to be a suitable dynamic failure criterion of LCES，and then the effort is focused on the confining pressure，cement content and EPS content effect on the dynamic strength properties of LCES. The test results indicate that the dynamic strength of LCES increases with the increasing confining pressure and cement content，however，the effect of confining pressure on the dynamic strength declines when the cement content increases. The dynamic strength of LCES initially increases and then decreases with the increase of EPS content，so LCES may has an optimal EPS content for the dynamic strength. Cement and EPS have considerable effects on the increase of the dynamic strength paramete of LCES，but they have few effects on the increase of the parameter jd. The relationship of dynamic shear strength and cyclic number(td-Nf) can be simulated by the power function properly. By considering synthetically the influences of confining pressure，cement content and EPS content，dynamic shear strength curves of LCES are normalized，and the dynamic strength formula is obtained.

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IMPROVED JOINT MODEL OF SHIELD TUNNEL SEGMENTS AND NUMERICAL CALCULATION OF INNER FORCES

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2007, 26 (S2): -4284 doi:
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[PDF 1044 KB] (720)

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The key issue for establishing calculating model of segments is to consider the influence of the joint and ground resisting force to the structure. The simplification of joint in the routine method model is improved. The calculation model which treats all the cross-section stiffness of segments as EI and the joint stiffness of segments as kEI coincides with the actual situation. Combining with the real data of the project of Beijing Metro Line No.10，the segments inner forces are calculated by the routine method model and its improved model，homogenous ring model and its improved model respectively. According to the numerical calculation results，the improvement of the rotating stiffness of joint in shield tunnel segments are found effective and feasible and also necessary；it can preliminarily determine that the reasonable stiffness reduction factor value of the rotating stiffness of joint in shield tunnel segments is 1/100–1/1 000.

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IMPROVED JOINT MODEL OF SHIELD TUNNEL SEGMENTS AND NUMERICAL CALCULATION OF INNER FORCES

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2007, 26 (S2): -4284 doi:
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[PDF 1044 KB] (885)

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The key issue for establishing calculating model of segments is to consider the influence of the joint and ground resisting force to the structure. The simplification of joint in the routine method model is improved. The calculation model which treats all the cross-section stiffness of segments as EI and the joint stiffness of segments as kEI coincides with the actual situation. Combining with the real data of the project of Beijing Metro Line No.10，the segments inner forces are calculated by the routine method model and its improved model，homogenous ring model and its improved model respectively. According to the numerical calculation results，the improvement of the rotating stiffness of joint in shield tunnel segments are found effective and feasible and also necessary；it can preliminarily determine that the reasonable stiffness reduction factor value of the rotating stiffness of joint in shield tunnel segments is 1/100–1/1 000.

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STUDY ON EARTH PRESSURES OF MULTI-STEP GEOGRID REINFORCED SOIL RETAINING WALL BY MODEL TEST

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2007, 26 (S2): -4292 doi:
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[PDF 505 KB] (538)

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An indoor model groove，which is 8.0 m long，3.0 m wide and 4.5 m high，was built to study the mechanical properties of multi-step geogrid reinforced wall. A series of model tests have been performed on the three-step reinforced wall with each step 1.5 m in height with two types of geogrid reinforcements in the groove. The earth pressures near the wall-plate，rear reinforced body and horizontal profile，the compression stress of the bottom，etc. are measured. It is found that the test data of the earth pressure in different points are inconsistent with the values calculated by the traditional earth pressure theory；and the pressure is closely associated with the mechanical behaviors and the height of the wall. At the same time，the displacement of the base is greatly impacted on the mechanical behaviors of the reinforced body whose pressure will be redistributed，i.e. when the displacement of base is large，the distribution of the pressure in ground is V-shaped；otherwise according to slash distribution. And it is shown that the earth pressure behind the panel is distributed with greater value in the middle and less ones at the bottom and the top. So are the earth pressures in the back of reinforced body，but the amplitude of prominent is smaller. It is also shown the mechanical behaviors in the reinforced body will be changed as the aperture of grid.

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STUDY ON EARTH PRESSURES OF MULTI-STEP GEOGRID REINFORCED SOIL RETAINING WALL BY MODEL TEST

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2007, 26 (S2): -4292 doi:
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[PDF 505 KB] (790)

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An indoor model groove，which is 8.0 m long，3.0 m wide and 4.5 m high，was built to study the mechanical properties of multi-step geogrid reinforced wall. A series of model tests have been performed on the three-step reinforced wall with each step 1.5 m in height with two types of geogrid reinforcements in the groove. The earth pressures near the wall-plate，rear reinforced body and horizontal profile，the compression stress of the bottom，etc. are measured. It is found that the test data of the earth pressure in different points are inconsistent with the values calculated by the traditional earth pressure theory；and the pressure is closely associated with the mechanical behaviors and the height of the wall. At the same time，the displacement of the base is greatly impacted on the mechanical behaviors of the reinforced body whose pressure will be redistributed，i.e. when the displacement of base is large，the distribution of the pressure in ground is V-shaped；otherwise according to slash distribution. And it is shown that the earth pressure behind the panel is distributed with greater value in the middle and less ones at the bottom and the top. So are the earth pressures in the back of reinforced body，but the amplitude of prominent is smaller. It is also shown the mechanical behaviors in the reinforced body will be changed as the aperture of grid.

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STUDY ON DISTRIBUTION LAWS OF ELASTIC MODULUS AND STRENGTH OF WARM FROZEN SOIL

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2007, 26 (S2): -4299 doi:
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[PDF 354 KB] (641)

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Because there are defects such as fracture and cavity in the warm frozen soil，and their distributions are random，the elastic moduli and strengths are still uncertain；and they will be stochastic variables submitted to one of probability distribution，even if the temperature of frozen soil is the same. To solve the problem mentioned above，the potential elastic modulus and strength distribution laws of warm frozen soil are analyzed systematically by using a large number of test data. The result shows that normal and logarithmic-normal distribution can describe probability distribution law of elastic modulus of warm frozen soil well；and Weibull distribution could reflect probability distribution law of its strength better. Finally，it is found that the strength of warm frozen soil is submitted to Weibull distribution；and reliability analysis of strength of warm frozen soil is analyzed.

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STUDY ON DISTRIBUTION LAWS OF ELASTIC MODULUS AND STRENGTH OF WARM FROZEN SOIL

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2007, 26 (S2): -4299 doi:
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[PDF 354 KB] (802)

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Because there are defects such as fracture and cavity in the warm frozen soil，and their distributions are random，the elastic moduli and strengths are still uncertain；and they will be stochastic variables submitted to one of probability distribution，even if the temperature of frozen soil is the same. To solve the problem mentioned above，the potential elastic modulus and strength distribution laws of warm frozen soil are analyzed systematically by using a large number of test data. The result shows that normal and logarithmic-normal distribution can describe probability distribution law of elastic modulus of warm frozen soil well；and Weibull distribution could reflect probability distribution law of its strength better. Finally，it is found that the strength of warm frozen soil is submitted to Weibull distribution；and reliability analysis of strength of warm frozen soil is analyzed.

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ONE-DIMENSIONAL CONSOLIDATION THEORY BASED ON HYPERBOLA MODEL UNDER TIME-DEPENDENT LOADING FOR SATURATED SOIL

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2007, 26 (S2): -4306 doi:
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[PDF 267 KB] (472)

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It is supposed that the constitutive relation of soil is the hyperbola model. The hyperbolic relationship between e and s ¢，which was achieved from this model，is applied to the study on one-dimensional nonlinear consolidation of one-layered and homogeneous saturated soil. With the assumptions that the decrease of the hydraulic conductivity is proportional to the decrease of the compression conductivity and the distribution of initial effective pressure does not vary with depth，the one-dimensional nonlinear partial differential consolidation equation，which is under arbitrary loading，is deduced. With the x -s ¢ transform，the nonlinear partial differential equation is changed into a linear one. According to the idiographic initial condition and the boundary conditions，the equation is then solved by using the variable separation method. Then the effective stress of soil and the excess water pore pressure can be achieved. So the correlation approach of the average consolidation degree，which is defined according to the settlement，and the correlation approach of the average consolidation degree that is defined according to the excess pore pressure are both deduced. The relevant computer program has been developed by MATLAB language. The results using this program are gained with the data from a specific example and the nonlinear consolidation theory with the same data. Both of the results are drawn in two charts. By comparing the curves from the charts，it is found that the differences between the two results are very small，which shows the rationality of this theory. The calculation shows that the consolidation degrees increase with the increment of time；and the value of the Us is a little bigger than that of the Up. When the consolidation equation is deduced，the different relationships between e and can be obtained. The different changing laws of hydraulic conductivity are adopted，and it clearly displays that the small differences in the results with the two different theories.

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ONE-DIMENSIONAL CONSOLIDATION THEORY BASED ON HYPERBOLA MODEL UNDER TIME-DEPENDENT LOADING FOR SATURATED SOIL

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2007, 26 (S2): -4306 doi:
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[PDF 267 KB] (612)

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It is supposed that the constitutive relation of soil is the hyperbola model. The hyperbolic relationship between e and s ¢，which was achieved from this model，is applied to the study on one-dimensional nonlinear consolidation of one-layered and homogeneous saturated soil. With the assumptions that the decrease of the hydraulic conductivity is proportional to the decrease of the compression conductivity and the distribution of initial effective pressure does not vary with depth，the one-dimensional nonlinear partial differential consolidation equation，which is under arbitrary loading，is deduced. With the x -s ¢ transform，the nonlinear partial differential equation is changed into a linear one. According to the idiographic initial condition and the boundary conditions，the equation is then solved by using the variable separation method. Then the effective stress of soil and the excess water pore pressure can be achieved. So the correlation approach of the average consolidation degree，which is defined according to the settlement，and the correlation approach of the average consolidation degree that is defined according to the excess pore pressure are both deduced. The relevant computer program has been developed by MATLAB language. The results using this program are gained with the data from a specific example and the nonlinear consolidation theory with the same data. Both of the results are drawn in two charts. By comparing the curves from the charts，it is found that the differences between the two results are very small，which shows the rationality of this theory. The calculation shows that the consolidation degrees increase with the increment of time；and the value of the Us is a little bigger than that of the Up. When the consolidation equation is deduced，the different relationships between e and can be obtained. The different changing laws of hydraulic conductivity are adopted，and it clearly displays that the small differences in the results with the two different theories.

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ANALYSIS OF SOIL MESO-STRUCTURE UNDER UPLIFT LOAD

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2007, 26 (S2): -4311 doi:
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[PDF 425 KB] (505)

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Meso-structure characterization of sand was studied on pile-bucket foundation bearing uplift load. Based on a series of uplift loading model tests，analysis of the failure modes and the development of slide rupture body in soil of pile-bucket foundation and the deformation process of soil is performed. Then soil meso-structure on plane of rupture and pile side is recorded with photos. Uplift failure of the pile-bucket foundation can be analyzed as compressive deformation of soil on the top part of the bucket-developed plastic zones—complete shear fracture of progressive failure. The frictional force of the bucket and pile will cause an increase in the shear stress of the soil surrounding the bucket and pile，and it will also cause developed plastic zones—complete shear fracture and progressive failure in the soil. The cracks on the surface of the soil are based on the centre of the concentric circle ring cracks in the centre of the foundation. The radius of the outer flank of the circle ring cracks has a good correlative relationship with the width of the foundation，about approximate 5.6 times against that of the bucket radius. Change of soil meso-structure characterization was researched. Load increasing，quantities of large pores increasing，and pore volumes will play leading roles in the change of soil structure；and gradually the direction of sand grains plays a leading role. Therefore，soil structure is loose，and contact points of grains are decreased；interlocking contact of grains are decreased. The grains have been marked directionality on plane of rupture. The relation of meso-structure parameters and pull strength on plane of rupture，porosity，incremental porosity，total grains，grains area and eccentricity of grains of rupture of plane have sudden change on uplift load；and their rates of change all are maximum. When load increasing and porosity are increased，the total grains，grains area and eccentricity are decreased. The porosity of soil structure of pile side is influenced by the uplift load，it will be influenced by pile sliding，and be influenced by general-shear failure. The results have important values on meso-mechanics study of subgrade bearing uplift load.

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ANALYSIS OF SOIL MESO-STRUCTURE UNDER UPLIFT LOAD

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2007, 26 (S2): -4311 doi:
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[PDF 425 KB] (541)

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Meso-structure characterization of sand was studied on pile-bucket foundation bearing uplift load. Based on a series of uplift loading model tests，analysis of the failure modes and the development of slide rupture body in soil of pile-bucket foundation and the deformation process of soil is performed. Then soil meso-structure on plane of rupture and pile side is recorded with photos. Uplift failure of the pile-bucket foundation can be analyzed as compressive deformation of soil on the top part of the bucket-developed plastic zones—complete shear fracture of progressive failure. The frictional force of the bucket and pile will cause an increase in the shear stress of the soil surrounding the bucket and pile，and it will also cause developed plastic zones—complete shear fracture and progressive failure in the soil. The cracks on the surface of the soil are based on the centre of the concentric circle ring cracks in the centre of the foundation. The radius of the outer flank of the circle ring cracks has a good correlative relationship with the width of the foundation，about approximate 5.6 times against that of the bucket radius. Change of soil meso-structure characterization was researched. Load increasing，quantities of large pores increasing，and pore volumes will play leading roles in the change of soil structure；and gradually the direction of sand grains plays a leading role. Therefore，soil structure is loose，and contact points of grains are decreased；interlocking contact of grains are decreased. The grains have been marked directionality on plane of rupture. The relation of meso-structure parameters and pull strength on plane of rupture，porosity，incremental porosity，total grains，grains area and eccentricity of grains of rupture of plane have sudden change on uplift load；and their rates of change all are maximum. When load increasing and porosity are increased，the total grains，grains area and eccentricity are decreased. The porosity of soil structure of pile side is influenced by the uplift load，it will be influenced by pile sliding，and be influenced by general-shear failure. The results have important values on meso-mechanics study of subgrade bearing uplift load.

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APPLICATION OF A MULTI-POINT GREY MODEL TO DEFORMATION PREDICTIN OF SUPPORTING STRUCTURE FOR DEEP PIT

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2007, 26 (S2): -4319 doi:
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[PDF 199 KB] (482)

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During the information construction times，with the aim of accurately predicting the deformation of supporting piles，the correlations between the measurement points in supporting piles should be taken into account in predicting the deformation of supporting structure for deep pit excavations；and the analysis of monitoring data and establishment of a proper model should be performed on the basis of the deformation behavior of the entirely deformed system；and because deformation of one measuring point has an influence on another in the same supporting pile of deep pit. Based on such concept，a single deformation prediction model is extended into a multi-point mode1 and coded with MATLAB. A multi-point prediction model is established，and its application to a case study is presented to verify the multi-point model. The results indicate that the proposed model is effective for predicting the deformation of supporting structures for deep excavations，more effective than the grey prediction model GM(1，1) for information construction of the engineering.

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APPLICATION OF A MULTI-POINT GREY MODEL TO DEFORMATION PREDICTIN OF SUPPORTING STRUCTURE FOR DEEP PIT

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2007, 26 (S2): -4319 doi:
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[PDF 199 KB] (760)

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During the information construction times，with the aim of accurately predicting the deformation of supporting piles，the correlations between the measurement points in supporting piles should be taken into account in predicting the deformation of supporting structure for deep pit excavations；and the analysis of monitoring data and establishment of a proper model should be performed on the basis of the deformation behavior of the entirely deformed system；and because deformation of one measuring point has an influence on another in the same supporting pile of deep pit. Based on such concept，a single deformation prediction model is extended into a multi-point mode1 and coded with MATLAB. A multi-point prediction model is established，and its application to a case study is presented to verify the multi-point model. The results indicate that the proposed model is effective for predicting the deformation of supporting structures for deep excavations，more effective than the grey prediction model GM(1，1) for information construction of the engineering.

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FINITE ELEMENT ANALYSIS OF DEEP EXCAVATION WITH BRACED RETAINING STRUCTURE OF DOUBLE-ROW PILES

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2007, 26 (S2): -4325 doi:
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[PDF 487 KB] (698)

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Braced retaining structure with double-row piles is a new type of retaining structure. The application of this type of retaining structure to an actual case is introduced. The behaviors of the excavation，such as the distribution of the deformations of retaining structure and earth pressure against the structure，are analyzed by FEM. An elastoplastic constitutive model，Drucker-Prager model，is adopted to simulate the behaviors of the soil. The analytical and measured results are compared. The differences between the theoretical data and the measured data are also analyzed. Finally the effects of the length of back-row pile，back-row pile spacing，spacing between the two rows of piles，top beam stiffness，and the strut stiffness are analyzed. The study shows that the deformations of the back-row piles are less than those of the front-row obviously. It also shows that the influences of the spacing between the two rows of piles and the strut stiffness are more distinct than the other factors.

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FINITE ELEMENT ANALYSIS OF DEEP EXCAVATION WITH BRACED RETAINING STRUCTURE OF DOUBLE-ROW PILES

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2007, 26 (S2): -4325 doi:
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[PDF 487 KB] (576)

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Braced retaining structure with double-row piles is a new type of retaining structure. The application of this type of retaining structure to an actual case is introduced. The behaviors of the excavation，such as the distribution of the deformations of retaining structure and earth pressure against the structure，are analyzed by FEM. An elastoplastic constitutive model，Drucker-Prager model，is adopted to simulate the behaviors of the soil. The analytical and measured results are compared. The differences between the theoretical data and the measured data are also analyzed. Finally the effects of the length of back-row pile，back-row pile spacing，spacing between the two rows of piles，top beam stiffness，and the strut stiffness are analyzed. The study shows that the deformations of the back-row piles are less than those of the front-row obviously. It also shows that the influences of the spacing between the two rows of piles and the strut stiffness are more distinct than the other factors.

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STUDY ON FOUNDATION TREATMENT THICKNESS AND TREATMENT METHOD FOR COLLAPSE LOESS WITH LARGE THICKNESS

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2007, 26 (S2): -4332 doi:
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[PDF 287 KB] (775)

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Foundation treatment method，treatment thickness and residual collapse settlement of collapse loess with large thickness are hot issues in engineering design in loess areas. Based on the collapse characteristics of collapse loess with large thickness，research work in three aspects related to collapse loess was conducted. Firstly，the principles of foundation treatment for collapse loess under overburden pressure with large thickness were expounded. Secondly，combining various sorts of buildings，the controlling standard of foundation treatment thickness and the residual collapse settlement were suggested. Thirdly，the applicabilities for whole treatment，local treatment of foundation and multiple treatment methods were discussed；and some successful examples for various treatment methods were introduced.

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STUDY ON FOUNDATION TREATMENT THICKNESS AND TREATMENT METHOD FOR COLLAPSE LOESS WITH LARGE THICKNESS

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2007, 26 (S2): -4332 doi:
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[PDF 287 KB] (921)

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Foundation treatment method，treatment thickness and residual collapse settlement of collapse loess with large thickness are hot issues in engineering design in loess areas. Based on the collapse characteristics of collapse loess with large thickness，research work in three aspects related to collapse loess was conducted. Firstly，the principles of foundation treatment for collapse loess under overburden pressure with large thickness were expounded. Secondly，combining various sorts of buildings，the controlling standard of foundation treatment thickness and the residual collapse settlement were suggested. Thirdly，the applicabilities for whole treatment，local treatment of foundation and multiple treatment methods were discussed；and some successful examples for various treatment methods were introduced.

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ELASTOPLASTIC ANALYSIS OF EXPANSION OF HEMISPHERE
CAVITY IN UNSATURATED SOIL CONSIDERING PILE
DRIVING VELOCITY

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2007, 26 (S2): -4339 doi:
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[PDF 248 KB] (487)

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The effect of pile driving velocity is considered. The movement status of the soil element in the elastoplastic interface is chosen as a reference criterion；and the stresses，displacements of any point in the field are described as the functions of R and r，which are the radius of plastic area and the distance of soil element to the center after the expansion respectively. The small-strain theory is used to obtain the equation that the relative velocity should be satisfied，and is defined as the ratio of the expansion velocity at r to the one on the elastoplastic interface，where the latter is composed of two parts：one is caused by the expansion itself —displacement velocity，another is supplemental velocity and is attributed to the deformation of the soil elements because of the expansion，which leads to the soil elements continuously going into plastic station. Finally，combining with the known condition of expansion velocity，the radius of plastic area and failure area of the soil around the pile after the pile driving can be deduced. The theories can provide instructions for some geotechnical engineering problems in unsaturated soil，such as the dynamic penetration of piles，ramming expanded pile and so on.

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ELASTOPLASTIC ANALYSIS OF EXPANSION OF HEMISPHERE
CAVITY IN UNSATURATED SOIL CONSIDERING PILE
DRIVING VELOCITY

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2007, 26 (S2): -4339 doi:
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[PDF 248 KB] (721)

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The effect of pile driving velocity is considered. The movement status of the soil element in the elastoplastic interface is chosen as a reference criterion；and the stresses，displacements of any point in the field are described as the functions of R and r，which are the radius of plastic area and the distance of soil element to the center after the expansion respectively. The small-strain theory is used to obtain the equation that the relative velocity should be satisfied，and is defined as the ratio of the expansion velocity at r to the one on the elastoplastic interface，where the latter is composed of two parts：one is caused by the expansion itself —displacement velocity，another is supplemental velocity and is attributed to the deformation of the soil elements because of the expansion，which leads to the soil elements continuously going into plastic station. Finally，combining with the known condition of expansion velocity，the radius of plastic area and failure area of the soil around the pile after the pile driving can be deduced. The theories can provide instructions for some geotechnical engineering problems in unsaturated soil，such as the dynamic penetration of piles，ramming expanded pile and so on.

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ANALYSIS OF RESULTS OF LARGE-SCALE TESTS ON TENSILE FORCE OF HDPE GEOMEMBRANE PLACED ON SIDE SLOPE IN LANDFILL

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2007, 26 (S2): -4343 doi:
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[PDF 268 KB] (333)

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The forces at the shoulder of geomembrane placed on the side slope as liner system in landfill are mainly temperature stress and tensile force due to waste compaction. In order to evaluate the temperature stress and tensile forces of high density polyethylene(HDPE) geomembrane in the liner system，which is composed of HDPE geomembrane and non-woven geotextile，the large-scale tests were conducted. The results show that the temperature stress within the HDPE geomembrane occurs with decrease of circumstantial temperature；the tensile force at the shoulder of HDPE geomembrane is mainly temperature stress when the height of soil is low；the tensile force of HDPE geomembrane by compaction work increases with the increase of height of soil. The tensile forces of HDPE geomembrane due to waste compaction are analyzed by finite element method；and the temperature stresses are analyzed by the relationship between temperature and the stress，the comparison shows that the calculation results considering stress relaxation of tensile force are closer to the test values.

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ANALYSIS OF RESULTS OF LARGE-SCALE TESTS ON TENSILE FORCE OF HDPE GEOMEMBRANE PLACED ON SIDE SLOPE IN LANDFILL

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2007, 26 (S2): -4343 doi:
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[PDF 268 KB] (496)

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The forces at the shoulder of geomembrane placed on the side slope as liner system in landfill are mainly temperature stress and tensile force due to waste compaction. In order to evaluate the temperature stress and tensile forces of high density polyethylene(HDPE) geomembrane in the liner system，which is composed of HDPE geomembrane and non-woven geotextile，the large-scale tests were conducted. The results show that the temperature stress within the HDPE geomembrane occurs with decrease of circumstantial temperature；the tensile force at the shoulder of HDPE geomembrane is mainly temperature stress when the height of soil is low；the tensile force of HDPE geomembrane by compaction work increases with the increase of height of soil. The tensile forces of HDPE geomembrane due to waste compaction are analyzed by finite element method；and the temperature stresses are analyzed by the relationship between temperature and the stress，the comparison shows that the calculation results considering stress relaxation of tensile force are closer to the test values.

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TEST STUDY ON GROUND SUBSIDENCE CAUSED BY METRO EXCAVATION IN LOESS AREA

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2007, 26 (S2): -4348 doi:
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[PDF 273 KB] (680)

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Construction of urban metro is becoming a hot issue in China，therefore，the prediction and control of ground subsidence caused by metro construction need special attention. Now，the centrifugal test is widely used to study the ground subsidence caused by metro excavation，but the factors that cause the ground subsidence are not the same in different strata. Because loess strata have the characteristics of seismic subsidence deformation and collapse，it is more difficult for construction of urban metro in loess area. To assess the different construction methods for metro excavation in loess trata，the in-situ measured date from line #2 of Xi¢an metro are considered. The four cases of geotechnical centrifugal model tests were carried on the instruments of Chang¢an University，China. The similarity ratio of test models and prototype soil body is 1∶60. A rectangular rigid container with internal dimensions of 700 mm×500 mm×360 mm was used in the centrifugal tests. Full-section construction method，mid-guiding hole and forward direction hole method，two side-wall pilot method and center diagram method were used in urban metro construction. The four kinds of construction methods on ground subsidence caused by metro excavation in loess strata were compared through centrifugal model tests. The research results show that the full-section construction method is the most effective method for metro tunneling in loess strata ；and the results also show that the primary consolidation is accounted of the majority of subsidence. This study provides a reliable foundation for urban metro design and construction in loess area.

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TEST STUDY ON GROUND SUBSIDENCE CAUSED BY METRO EXCAVATION IN LOESS AREA

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2007, 26 (S2): -4348 doi:
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[PDF 273 KB] (400)

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Construction of urban metro is becoming a hot issue in China，therefore，the prediction and control of ground subsidence caused by metro construction need special attention. Now，the centrifugal test is widely used to study the ground subsidence caused by metro excavation，but the factors that cause the ground subsidence are not the same in different strata. Because loess strata have the characteristics of seismic subsidence deformation and collapse，it is more difficult for construction of urban metro in loess area. To assess the different construction methods for metro excavation in loess trata，the in-situ measured date from line #2 of Xi¢an metro are considered. The four cases of geotechnical centrifugal model tests were carried on the instruments of Chang¢an University，China. The similarity ratio of test models and prototype soil body is 1∶60. A rectangular rigid container with internal dimensions of 700 mm×500 mm×360 mm was used in the centrifugal tests. Full-section construction method，mid-guiding hole and forward direction hole method，two side-wall pilot method and center diagram method were used in urban metro construction. The four kinds of construction methods on ground subsidence caused by metro excavation in loess strata were compared through centrifugal model tests. The research results show that the full-section construction method is the most effective method for metro tunneling in loess strata ；and the results also show that the primary consolidation is accounted of the majority of subsidence. This study provides a reliable foundation for urban metro design and construction in loess area.

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PARAMETRIC STUDY ON EMBANKMENT-GROUND VIBRATIONS GENERATED BY TRAIN MOVING LOADS

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2007, 26 (S2): -4353 doi:
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In order to predict and evaluate track and embankment vibrations generated by train moving load and wave propagation in adjoining ground，a coupled dynamic interaction model for track and underlying ground under moving loads was developed by employing the 2.5D finite element method，and dynamic responses of three-dimensional ground were obtained. Multi-wheel axle train loadings were considered to study the track and ground vibrations both for low-speed and high-speed cases；and computation results were illustrated to show the ground response characteristics. Extensive parametric studies were performed to assess influences of several controlling parameters，including track stiffness，embankment height，shear wave velocity and damping ratio of underlying ground soil，train speed and its vibration frequency. The analytical results obtained in the current study are important to analyze the running stability of high-speed train on soft soil ground and to evaluate its vibration impact to adjoining ground along raillines.

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PARAMETRIC STUDY ON EMBANKMENT-GROUND VIBRATIONS GENERATED BY TRAIN MOVING LOADS

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2007, 26 (S2): -4353 doi:
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[PDF 549 KB] (896)

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In order to predict and evaluate track and embankment vibrations generated by train moving load and wave propagation in adjoining ground，a coupled dynamic interaction model for track and underlying ground under moving loads was developed by employing the 2.5D finite element method，and dynamic responses of three-dimensional ground were obtained. Multi-wheel axle train loadings were considered to study the track and ground vibrations both for low-speed and high-speed cases；and computation results were illustrated to show the ground response characteristics. Extensive parametric studies were performed to assess influences of several controlling parameters，including track stiffness，embankment height，shear wave velocity and damping ratio of underlying ground soil，train speed and its vibration frequency. The analytical results obtained in the current study are important to analyze the running stability of high-speed train on soft soil ground and to evaluate its vibration impact to adjoining ground along raillines.

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MODEL EXPERIMENTAL STUDY ON MECHANICAL CHARACTERISTICS OF ROUND-SHAPED FROZEN SOIL WALL IN DEEP PIT

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2007, 26 (S2): -4362 doi:
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[PDF 251 KB] (297)

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In order to understand the artificial freezing technology employed in the deep pit，a physical model test of stress and deformation of large diameter round-shaped frozen soil wall was carried out on a self-developed large test rig. The laws were obtained among the horizontal displacement of the frozen soil wall and the factors of the excavation depth，frozen soil wall diameter，and the average of temperature of frozen soil. The changing laws in the exposure of frozen soil wall were also obtained. The results show that the horizontal displacement of wall increases as the depth and diameter increase during excavation，but decrease as the average of temperature decreases. The horizontal displacement of the exposure of frozen soil wall increases as the excavation depth increases，and the characteristics of the larger deformation in the center and the smaller ones in both sides were obtained. There are the different ratios of elastic displacement to the total displacement under different temperatures，and it increases from 30%(－4 ℃) to 90%(－18 ℃). The analysis indicates that the diameter and depth of foundation pit are the major factors that affect horizontal displacement of the frozen soil wall，and the effects of average of temperature，wall thickness and excavation height are comparatively smaller.

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MODEL EXPERIMENTAL STUDY ON MECHANICAL CHARACTERISTICS OF ROUND-SHAPED FROZEN SOIL WALL IN DEEP PIT

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2007, 26 (S2): -4362 doi:
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[PDF 251 KB] (649)

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In order to understand the artificial freezing technology employed in the deep pit，a physical model test of stress and deformation of large diameter round-shaped frozen soil wall was carried out on a self-developed large test rig. The laws were obtained among the horizontal displacement of the frozen soil wall and the factors of the excavation depth，frozen soil wall diameter，and the average of temperature of frozen soil. The changing laws in the exposure of frozen soil wall were also obtained. The results show that the horizontal displacement of wall increases as the depth and diameter increase during excavation，but decrease as the average of temperature decreases. The horizontal displacement of the exposure of frozen soil wall increases as the excavation depth increases，and the characteristics of the larger deformation in the center and the smaller ones in both sides were obtained. There are the different ratios of elastic displacement to the total displacement under different temperatures，and it increases from 30%(－4 ℃) to 90%(－18 ℃). The analysis indicates that the diameter and depth of foundation pit are the major factors that affect horizontal displacement of the frozen soil wall，and the effects of average of temperature，wall thickness and excavation height are comparatively smaller.

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A DAMAGE CONSTITUTIVE MODEL FOR SANDY SOIL BASED ON ANALYSIS OF GRAIN SLIDING

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2007, 26 (S2): -4367 doi:
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[PDF 273 KB] (476)

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The experimental results reveal that the deformation of sandy soil has the characteristics as follows：nonlinear elastoplastic deformation，shear dilation and relativity of stress path. It is deemed that the sliding of grains in sand will contribute to these deformation characteristics. The contact among grains can be classified as perfect contact and sliding contact. When the shear stress reaches to the shear strength on the interfaces of grains，the contact will be transformed from perfect contact to sliding contact. The conversion of the contact among grains is regarded as damage in the sand skeleton. Two direction-region values of the sliding interfaces can be calculated：the one expressed as is used to describe the direction region in the damage phase and the other one expressed as is used to describe the direction region when the sand skeleton is subjected to failure. The ratio of to is defined as damage ratio and a damage constitutive model is proposed. The model properties can be determined through conventional triaxial compression test and constant stress ratio consolidation test. The model is capable of predicting deformation behaviors for various conditions，including varying hydrostatic stresses，consolidation conditions and stress paths. The achieved test results on the versatility of the proposed model indicate that the proposed model can rationally describe the deformation characteristics of sand.

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A DAMAGE CONSTITUTIVE MODEL FOR SANDY SOIL BASED ON ANALYSIS OF GRAIN SLIDING

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2007, 26 (S2): -4367 doi:
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[PDF 273 KB] (639)

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The experimental results reveal that the deformation of sandy soil has the characteristics as follows：nonlinear elastoplastic deformation，shear dilation and relativity of stress path. It is deemed that the sliding of grains in sand will contribute to these deformation characteristics. The contact among grains can be classified as perfect contact and sliding contact. When the shear stress reaches to the shear strength on the interfaces of grains，the contact will be transformed from perfect contact to sliding contact. The conversion of the contact among grains is regarded as damage in the sand skeleton. Two direction-region values of the sliding interfaces can be calculated：the one expressed as is used to describe the direction region in the damage phase and the other one expressed as is used to describe the direction region when the sand skeleton is subjected to failure. The ratio of to is defined as damage ratio and a damage constitutive model is proposed. The model properties can be determined through conventional triaxial compression test and constant stress ratio consolidation test. The model is capable of predicting deformation behaviors for various conditions，including varying hydrostatic stresses，consolidation conditions and stress paths. The achieved test results on the versatility of the proposed model indicate that the proposed model can rationally describe the deformation characteristics of sand.

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ONE-DIMENSIONAL NONLINEAR CONSOLIDATION CONSIDERING BURIED DEPTH OF SATURATED CLAY LAYER

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2007, 26 (S2): -4372 doi:
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[PDF 281 KB] (557)

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The buried depth of saturated clay layer has great influence on the initial effective stress distribution，and consequently on the characteristics of its nonlinear consolidation. Based on the well-known assumption of the linear relation between the pore ratio and the logarithm of effective stress or permeability conductivity，the one-dimensional nonlinear consolidation equation considering the effects of the initial effective stress distribution is generalized to consider the buried depth of saturated clay layer，and numerical analysis is performed by using finite volume method. In order to verify its validity，the numerical solution by the present method for the case that the initial effective stress is constant with the depth and the ratio of the compressibility index to the permeability index that is equal to 1 is compared with the analytical solution based on the nonlinear consolidation theory proposed by E. H. Davis and G. P. Raymond. Then the effects of some parameters such as the buried depth of clay layer，the ratio of the compressibility index to the permeability index and the value of the vertical uniform load on the consolidation process are investigated. The numerical results indicate that the rate of settlement of clay layer decreases as these three parameters increase respectively，while the effect of the buried depth of clay layer on the dissipative process of pore water pressure is restricted by the ratio of compressibility index to permeability index.

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ONE-DIMENSIONAL NONLINEAR CONSOLIDATION CONSIDERING BURIED DEPTH OF SATURATED CLAY LAYER

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2007, 26 (S2): -4372 doi:
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[PDF 281 KB] (714)

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Show Abstract

The buried depth of saturated clay layer has great influence on the initial effective stress distribution，and consequently on the characteristics of its nonlinear consolidation. Based on the well-known assumption of the linear relation between the pore ratio and the logarithm of effective stress or permeability conductivity，the one-dimensional nonlinear consolidation equation considering the effects of the initial effective stress distribution is generalized to consider the buried depth of saturated clay layer，and numerical analysis is performed by using finite volume method. In order to verify its validity，the numerical solution by the present method for the case that the initial effective stress is constant with the depth and the ratio of the compressibility index to the permeability index that is equal to 1 is compared with the analytical solution based on the nonlinear consolidation theory proposed by E. H. Davis and G. P. Raymond. Then the effects of some parameters such as the buried depth of clay layer，the ratio of the compressibility index to the permeability index and the value of the vertical uniform load on the consolidation process are investigated. The numerical results indicate that the rate of settlement of clay layer decreases as these three parameters increase respectively，while the effect of the buried depth of clay layer on the dissipative process of pore water pressure is restricted by the ratio of compressibility index to permeability index.

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THREE-PART WEDGE METHOD FOR TRANSLATIONAL SLIDING ANALYSES OF LANDFILLS RETAINED BY A TOE DAM

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2007, 26 (S2): -4378 doi:
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[PDF 390 KB] (674)

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The three-part wedge method for translational failure analyses of landfills retained by a toe dam was presented；and the approximate solution of the factor of safety was also given. With this approximate solution，analyses of the stability of new and expanded landfills along the back and bottom linings can be considerably simplified. Thus it is an acceptable method for the engineering application. Computed results by the proposed method are in good agreement with those by the Spencer¢s method. Moreover，it can take into account the effect of the internal friction angle of the waste on the factor of safety. Parametric studies show that the interface strength of the lining determines the stability of the landfill along the lining. The angles of slopes，the height and width of the landfills and the height of the toe dam also greatly influence the sliding of the landfill along the lining. For the expanded landfill，more attentions should be paid to the failure along the intermediate lining between the existing and expansion wastes. Additionally，the wider the landfill expands horizontally，the better the stability along the intermediate lining is.

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THREE-PART WEDGE METHOD FOR TRANSLATIONAL SLIDING ANALYSES OF LANDFILLS RETAINED BY A TOE DAM

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2007, 26 (S2): -4378 doi:
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[PDF 390 KB] (597)

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Show Abstract

The three-part wedge method for translational failure analyses of landfills retained by a toe dam was presented；and the approximate solution of the factor of safety was also given. With this approximate solution，analyses of the stability of new and expanded landfills along the back and bottom linings can be considerably simplified. Thus it is an acceptable method for the engineering application. Computed results by the proposed method are in good agreement with those by the Spencer¢s method. Moreover，it can take into account the effect of the internal friction angle of the waste on the factor of safety. Parametric studies show that the interface strength of the lining determines the stability of the landfill along the lining. The angles of slopes，the height and width of the landfills and the height of the toe dam also greatly influence the sliding of the landfill along the lining. For the expanded landfill，more attentions should be paid to the failure along the intermediate lining between the existing and expansion wastes. Additionally，the wider the landfill expands horizontally，the better the stability along the intermediate lining is.

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MONITORING AND ANALYSIS OF LATERAL DEFORMATION OF RETAINING WALL DURING BOTTOM EXCAVATION IN DEEP PIT

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2007, 26 (S2): -4386 doi:
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[PDF 420 KB] (652)

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Controlling the lateral deformation of retaining wall is one of the hot issues in deep excavation，and the lateral deformation during bottom excavation occupies considerable proportion of that in the whole excavation works. Based on measured data and practical work of a metro station construction in Shanghai City，lateral displacement with different soil exposure times during excavation is analyzed. As a result，the exposure time of bottom soil has notable influence on the retaining wall¢s lateral deformation during the periods of both soil exposure and bottom excavation. As the increasing of soil exposure time，incremental lateral deformation of retaining wall on the stage of bottom excavation construction can reach 30 percent of the total displacement. Shortening soil exposure time is the key point of controlling lateral displacement on the stage of bottom excavation. In addition，concrete cushion plays critical bracing function on controlling lateral deformation of the retaining wall，which is similar to the reinforcement concrete bottom plate. Accelerating the construction of concrete cushion as soon as possible can make full use of bracing effect on controlling the lateral deformation of retaining wall. Bracing effect of concrete cushion depends on several factors，such as concrete cushion¢s strength，stiff and flatness. The effect can be weakened with debasement of concrete cushion¢s entirety. Some proposals for lateral deformation controlling during bottom excavation of deep pit are offered. Shortening bottom excavation soil exposure time and bottom construction time are favorable of lateral deformation controlling. Increasing concrete cushion¢s entirety and promoting construction progress of the reinforcement concrete bottom plate can reduce retaining wall¢s lateral deformation on the excavation stage. The results can provide references to other similar deep excavation engineering.

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MONITORING AND ANALYSIS OF LATERAL DEFORMATION OF RETAINING WALL DURING BOTTOM EXCAVATION IN DEEP PIT

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2007, 26 (S2): -4386 doi:
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[PDF 420 KB] (697)

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Show Abstract

Controlling the lateral deformation of retaining wall is one of the hot issues in deep excavation，and the lateral deformation during bottom excavation occupies considerable proportion of that in the whole excavation works. Based on measured data and practical work of a metro station construction in Shanghai City，lateral displacement with different soil exposure times during excavation is analyzed. As a result，the exposure time of bottom soil has notable influence on the retaining wall¢s lateral deformation during the periods of both soil exposure and bottom excavation. As the increasing of soil exposure time，incremental lateral deformation of retaining wall on the stage of bottom excavation construction can reach 30 percent of the total displacement. Shortening soil exposure time is the key point of controlling lateral displacement on the stage of bottom excavation. In addition，concrete cushion plays critical bracing function on controlling lateral deformation of the retaining wall，which is similar to the reinforcement concrete bottom plate. Accelerating the construction of concrete cushion as soon as possible can make full use of bracing effect on controlling the lateral deformation of retaining wall. Bracing effect of concrete cushion depends on several factors，such as concrete cushion¢s strength，stiff and flatness. The effect can be weakened with debasement of concrete cushion¢s entirety. Some proposals for lateral deformation controlling during bottom excavation of deep pit are offered. Shortening bottom excavation soil exposure time and bottom construction time are favorable of lateral deformation controlling. Increasing concrete cushion¢s entirety and promoting construction progress of the reinforcement concrete bottom plate can reduce retaining wall¢s lateral deformation on the excavation stage. The results can provide references to other similar deep excavation engineering.

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STUDY ON INSULATING LAYER THICKNESS BY PHASE-CHANGE TEMPERATURE FIELD OF HIGHWAY TUNNEL IN COLD REGION

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2007, 26 (S2): -4395 doi:
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[PDF 487 KB] (567)

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Highway tunnel in cold region is generally influenced by freezing-thawing and frost-heave action. Disaster problems of tunnels are unavoidably induced，which will not only affect regular tunnel service，but also endanger long-term safety of tunnel. Based on climate characteristics of high-cold highway tunnel，outer insulating layer is selected as frost-resistant measures；and phase-change temperature field of finite element model is adopted to comparatively analyze the heat-insulating properties of different insulating materials and different thicknesses. In-situ test is used to verify the distribution of temperature field after insulating layer being considered；and performances of different insulating layers are also testified. Suitable insulating materials and corresponding thicknesses are provided for practical engineering.

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STUDY ON INSULATING LAYER THICKNESS BY PHASE-CHANGE TEMPERATURE FIELD OF HIGHWAY TUNNEL IN COLD REGION

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2007, 26 (S2): -4395 doi:
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[PDF 487 KB] (790)

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Show Abstract

Highway tunnel in cold region is generally influenced by freezing-thawing and frost-heave action. Disaster problems of tunnels are unavoidably induced，which will not only affect regular tunnel service，but also endanger long-term safety of tunnel. Based on climate characteristics of high-cold highway tunnel，outer insulating layer is selected as frost-resistant measures；and phase-change temperature field of finite element model is adopted to comparatively analyze the heat-insulating properties of different insulating materials and different thicknesses. In-situ test is used to verify the distribution of temperature field after insulating layer being considered；and performances of different insulating layers are also testified. Suitable insulating materials and corresponding thicknesses are provided for practical engineering.

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APPLICATION OF BP NETWORK TO TESTS ON FRACTAL CHARACTERISTICS OF COARSE CROSS-SECTIONS

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2007, 26 (S2): -4402 doi:
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[PDF 511 KB] (516)

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With the results from scanning of laser profilometer to plaster fracture surface，the dimension Ds and intercept As of coarse surface are obtained on the basis of dimension calculation theory—cubic covering method. Along x- and y-directions，the surface is cut with scanning space(0.2 mm). Based on curve dimension theory—box-dimension method，the dimensions and intercepts of all curves are calculated. Then x- and y-direction dimension average values(Dx，Dy ) and intercept average values(Ax，Ay) are all gained. Logical relation among intercept average values of x-direction and y-direction—Ax and Ay，and surface intercept As are explored on the premise of different surface dimensions. By constructing BP artificial neural network with early stopping，mutual relations between the two parameters－dimension Ds and intercept As and four parameters，i.e. x- and y-direction dimension average values(Dx ，Dy) and intercept mean values(Ax，Ay) are disclosed.

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APPLICATION OF BP NETWORK TO TESTS ON FRACTAL CHARACTERISTICS OF COARSE CROSS-SECTIONS

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2007, 26 (S2): -4402 doi:
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[PDF 511 KB] (712)

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Show Abstract

With the results from scanning of laser profilometer to plaster fracture surface，the dimension Ds and intercept As of coarse surface are obtained on the basis of dimension calculation theory—cubic covering method. Along x- and y-directions，the surface is cut with scanning space(0.2 mm). Based on curve dimension theory—box-dimension method，the dimensions and intercepts of all curves are calculated. Then x- and y-direction dimension average values(Dx，Dy ) and intercept average values(Ax，Ay) are all gained. Logical relation among intercept average values of x-direction and y-direction—Ax and Ay，and surface intercept As are explored on the premise of different surface dimensions. By constructing BP artificial neural network with early stopping，mutual relations between the two parameters－dimension Ds and intercept As and four parameters，i.e. x- and y-direction dimension average values(Dx ，Dy) and intercept mean values(Ax，Ay) are disclosed.

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TEST STUDY ON STRESS AND DEFORMATION BEHAVIORS OF COMPOSITE SOIL-NAILED SUPPORT WITH PRECIPITATION

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2007, 26 (S2): -4410 doi:
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[PDF 470 KB] (408)

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Based on the established similarity law and tests of filled up slope failure model and soil-nailed supporting mechanism，test study on the stress and deformation behaviors of soil-nails in continuous and intensive precipitation was conducted. The achieved results are listed as follows：(1) it is one of necessary working processes to construct the closing concrete layer and the advanced vertical anchor pipe for supporting backfilled sidewall or slope with composite soil-nailed technique；(2) after being permeated with precipitation，the backfilled soil grains have the tendency to obtain the minimum potential energy，which means the soil has liquidity tendency and the rigid motion assumption is not suitable for analyzing the stability of backfilled sidewall or slope；and (3) the critical point of penetration speed increment is the key factor to control landslide. It is found that the critical point of the precipitation speed increment is 15.5 cm/d；and sedimentation and landslide will happen when the precipitation speed increment reaches or exceeds the critical point.

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TEST STUDY ON STRESS AND DEFORMATION BEHAVIORS OF COMPOSITE SOIL-NAILED SUPPORT WITH PRECIPITATION

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2007, 26 (S2): -4410 doi:
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[PDF 470 KB] (556)

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Show Abstract

Based on the established similarity law and tests of filled up slope failure model and soil-nailed supporting mechanism，test study on the stress and deformation behaviors of soil-nails in continuous and intensive precipitation was conducted. The achieved results are listed as follows：(1) it is one of necessary working processes to construct the closing concrete layer and the advanced vertical anchor pipe for supporting backfilled sidewall or slope with composite soil-nailed technique；(2) after being permeated with precipitation，the backfilled soil grains have the tendency to obtain the minimum potential energy，which means the soil has liquidity tendency and the rigid motion assumption is not suitable for analyzing the stability of backfilled sidewall or slope；and (3) the critical point of penetration speed increment is the key factor to control landslide. It is found that the critical point of the precipitation speed increment is 15.5 cm/d；and sedimentation and landslide will happen when the precipitation speed increment reaches or exceeds the critical point.

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A MACROSCOPIC WATER UPTAKE MODEL OF TREE ROOTS
AND ITS VERIFICATION

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2007, 26 (S2): -4417 doi:
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[PDF 410 KB] (770)

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Soil water extracted by tree roots can cause significant decrease of the soil water content and eventually lead to ground settlement. Understanding water uptake by tree roots will help to know the influence of tree on the ground settlement. The main objective of this paper is to develop a flexible and applicable root water uptake model for trees. For this purpose，a serious of measurements and tests were firstly conducted in an experimental citrus orchard，including experimental studies on water kinematical parameters of the unsaturated soil，monitoring of the soil water potential，survey of citrus roots and observation of meteorological elements. And then an inverse calculation method of soil water movement was demonstrated. With this method，root soil water uptake rates can be obtained when the soil water potentials are available. Based on the measured data，a root water uptake model was developed using multiple regression analysis method. The root water uptake pattern calculated using this root water uptake model is approximate to the measured root water uptake pattern. Compared with the existing root water uptake models，the model has some advantages in following aspects：firstly，it contains only three easily determined influencing factors，i.e. evaporation of water from water surface，root density function and soil water potential，which make its application very convenient. Secondly，unlike all the existing microscopic root water uptake models that assume root water uptake rate being proportional to root length density，this paper defines root density as the mass of effective dry roots within a unit soil bulk volume because water uptake rate of activity root depends on both the root length and the root radius，and also considers that root water uptake rate is an exponential function of root density because the adjacent roots are limited each other to extract soil water. Finally，in this model，four undetermined parameters account for the point of maximum root density and the point of zero root density，which make the root water uptake model universally be suitable for all plants and allow spatial variations of water uptake rate. The four parameters can be easily determined through root density measurement.

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A MACROSCOPIC WATER UPTAKE MODEL OF TREE ROOTS
AND ITS VERIFICATION

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2007, 26 (S2): -4419 doi:
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[PDF 410 KB] (651)

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Show Abstract

Soil water extracted by tree roots can cause significant decrease of the soil water content and eventually lead to ground settlement. Understanding water uptake by tree roots will help to know the influence of tree on the ground settlement. The main objective of this paper is to develop a flexible and applicable root water uptake model for trees. For this purpose，a serious of measurements and tests were firstly conducted in an experimental citrus orchard，including experimental studies on water kinematical parameters of the unsaturated soil，monitoring of the soil water potential，survey of citrus roots and observation of meteorological elements. And then an inverse calculation method of soil water movement was demonstrated. With this method，root soil water uptake rates can be obtained when the soil water potentials are available. Based on the measured data，a root water uptake model was developed using multiple regression analysis method. The root water uptake pattern calculated using this root water uptake model is approximate to the measured root water uptake pattern. Compared with the existing root water uptake models，the model has some advantages in following aspects：firstly，it contains only three easily determined influencing factors，i.e. evaporation of water from water surface，root density function and soil water potential，which make its application very convenient. Secondly，unlike all the existing microscopic root water uptake models that assume root water uptake rate being proportional to root length density，this paper defines root density as the mass of effective dry roots within a unit soil bulk volume because water uptake rate of activity root depends on both the root length and the root radius，and also considers that root water uptake rate is an exponential function of root density because the adjacent roots are limited each other to extract soil water. Finally，in this model，four undetermined parameters account for the point of maximum root density and the point of zero root density，which make the root water uptake model universally be suitable for all plants and allow spatial variations of water uptake rate. The four parameters can be easily determined through root density measurement.

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COMPREHENSIVE CONTROLLED BLASTING TECHNIQUE FOR TGP SHIPLOCK

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2007, 26 (S2): -4426 doi:
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[PDF 314 KB] (637)

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The earth and rock excavation volumes of the permanent shiplock account for 40 percent of the total of the whole Three Gorges Project(TGP). The study of the excavation technique is quite systematic and comprehensive to guarantee the construction success. The study includes the blasting gears and materials，blasting mode，parameters of blasting，initiating connection，control index of the velocity of particle vibration of rock，thickness of lateral preserved protective layer during trench excavation，thickness of the protective layer of bed rock，control index of initiating charge for single interval，assortment of explosive，construction tools and equipment as well as construction technology. The excavation technique adopted for the vertical walls is more reliable and much safer compared with the excavation mode such as pre-split blasting to excavate at one time or other modes. This technology is able to satisfy the requirements of construction quality and construction progress，successfully facing the challenge of the excavation of the world-class high vertical slopes of the permanent navigation shiplock.

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COMPREHENSIVE CONTROLLED BLASTING TECHNIQUE FOR TGP SHIPLOCK

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2007, 26 (S2): -4426 doi:
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[PDF 314 KB] (767)

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Show Abstract

The earth and rock excavation volumes of the permanent shiplock account for 40 percent of the total of the whole Three Gorges Project(TGP). The study of the excavation technique is quite systematic and comprehensive to guarantee the construction success. The study includes the blasting gears and materials，blasting mode，parameters of blasting，initiating connection，control index of the velocity of particle vibration of rock，thickness of lateral preserved protective layer during trench excavation，thickness of the protective layer of bed rock，control index of initiating charge for single interval，assortment of explosive，construction tools and equipment as well as construction technology. The excavation technique adopted for the vertical walls is more reliable and much safer compared with the excavation mode such as pre-split blasting to excavate at one time or other modes. This technology is able to satisfy the requirements of construction quality and construction progress，successfully facing the challenge of the excavation of the world-class high vertical slopes of the permanent navigation shiplock.

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DATABASE FOR SLOPES RELATED TO CHINA¢S WATER RESOURCES AND HYDROPOWER DEVELOPMENTS USING XML

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2007, 26 (S2): -4432 doi:
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[PDF 302 KB] (611)

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The database of slopes related to the water resources and hydropower developments are introduced briefly. This database are based on the 117 slope cases selected by Chinese hydroelectric workers in the past years. The contents of this database are very abundant，including the basic geology information，excavation and control design and monitoring aspect，and so on. And at same time，all slope cases in database are divided according to the slope property，the height and stability status of slopes，rock mass structures，the failure modes and the triggering factors of failures. This paper introduces the results of classification and arrangement of slope cases by using tables. This slope database can provide important references to the design and construction of slopes in similar places future. At present，the advanced computer technology has made this database possible to share on the internet. XML(extensible markup language) has many advantages，so it is applied widely in web field. Combined with SQL Sever 2000，it can provide the technology support of sharing the database in web. Taking the Manwan hydroelectric power station left bank slope as an example，the application of XML technology to the slope database is explained，and the method of constructing the database shared in network is simply illustrated.

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DATABASE FOR SLOPES RELATED TO CHINA¢S WATER RESOURCES AND HYDROPOWER DEVELOPMENTS USING XML

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2007, 26 (S2): -4432 doi:
Full Text:

[PDF 302 KB] (606)

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Show Abstract

The database of slopes related to the water resources and hydropower developments are introduced briefly. This database are based on the 117 slope cases selected by Chinese hydroelectric workers in the past years. The contents of this database are very abundant，including the basic geology information，excavation and control design and monitoring aspect，and so on. And at same time，all slope cases in database are divided according to the slope property，the height and stability status of slopes，rock mass structures，the failure modes and the triggering factors of failures. This paper introduces the results of classification and arrangement of slope cases by using tables. This slope database can provide important references to the design and construction of slopes in similar places future. At present，the advanced computer technology has made this database possible to share on the internet. XML(extensible markup language) has many advantages，so it is applied widely in web field. Combined with SQL Sever 2000，it can provide the technology support of sharing the database in web. Taking the Manwan hydroelectric power station left bank slope as an example，the application of XML technology to the slope database is explained，and the method of constructing the database shared in network is simply illustrated.

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COMPLEX EVALUATION ON STABILITY OF HIGH GRAVITY RETAINING WALL OF YIXING PUMPED-STORAGE POWER STATION

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2007, 26 (S2): -4439 doi:
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[PDF 456 KB] (527)

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Limited by the topography and geological condition，the main dam of the up-reservoir of Yixing pumped-storage power station has to be located on a slope. The main dam is a combination of a rockfill dam and a high concrete gravity retaining wall(45.9 m)，which are very seldom seen nowadays in the world. How to maintain the safety of the high concrete gravity retaining wall on the slope under the great thrust caused by the rockfill of the dam is a hot issue. According to the monitoring data and the 3D FE numerical analysis，the value and the development law of the pressure of rockfill on the back of retaining wall can be obtained，and also the location and direction of the pressures on three typical sections. The location of the action point of resultant is at 40%–45% of the wall height，which verifies the Terzaghi¢s viewpoint that the location of the force point is not at one-third of the wall height，but is about at 40% of the wall height. On these basis，the safety factor of the concrete retaining wall under the running condition is analyzed，so as to evaluate the anti-slide and anti-inclination ability stability of the high concrete gravity retaining wall.

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COMPLEX EVALUATION ON STABILITY OF HIGH GRAVITY RETAINING WALL OF YIXING PUMPED-STORAGE POWER STATION

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2007, 26 (S2): -4439 doi:
Full Text:

[PDF 456 KB] (662)

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Show Abstract

Limited by the topography and geological condition，the main dam of the up-reservoir of Yixing pumped-storage power station has to be located on a slope. The main dam is a combination of a rockfill dam and a high concrete gravity retaining wall(45.9 m)，which are very seldom seen nowadays in the world. How to maintain the safety of the high concrete gravity retaining wall on the slope under the great thrust caused by the rockfill of the dam is a hot issue. According to the monitoring data and the 3D FE numerical analysis，the value and the development law of the pressure of rockfill on the back of retaining wall can be obtained，and also the location and direction of the pressures on three typical sections. The location of the action point of resultant is at 40%–45% of the wall height，which verifies the Terzaghi¢s viewpoint that the location of the force point is not at one-third of the wall height，but is about at 40% of the wall height. On these basis，the safety factor of the concrete retaining wall under the running condition is analyzed，so as to evaluate the anti-slide and anti-inclination ability stability of the high concrete gravity retaining wall.

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INTELLIGENT INVERSION OF EXCAVATION DISPLACEMENT FOR UNDERGROUND POWER-HOUSE OF LANGYASHAN PUMPED-STORAGE POWER STATION

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2007, 26 (S2): -4446 doi:
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[PDF 231 KB] (595)

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Based on orthogonal design，difference method，neural networks and genetic algorithms，the intelligent inversion is performed for the excavation displacement of underground powerhouse of Langyashan pumped- storage power station. Referring to the geological data，the different parameters and levels are chosen for rock and dike according to orthogonal design. The related analytical samples for neural networks are given by FLAC3D calculation. Through training the neural network with samples，the optimized inversion parameters are obtained by seeking for the optimum of genetic algorithms. The obtained parameters are used to calculate by FLAC3D and the results agree well with the in-situ measurement data.

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INTELLIGENT INVERSION OF EXCAVATION DISPLACEMENT FOR UNDERGROUND POWER-HOUSE OF LANGYASHAN PUMPED-STORAGE POWER STATION

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2007, 26 (S2): -4447 doi:
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[PDF 231 KB] (661)

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Based on orthogonal design，difference method，neural networks and genetic algorithms，the intelligent inversion is performed for the excavation displacement of underground powerhouse of Langyashan pumped- storage power station. Referring to the geological data，the different parameters and levels are chosen for rock and dike according to orthogonal design. The related analytical samples for neural networks are given by FLAC3D calculation. Through training the neural network with samples，the optimized inversion parameters are obtained by seeking for the optimum of genetic algorithms. The obtained parameters are used to calculate by FLAC3D and the results agree well with the in-situ measurement data.

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STUDY ON STABILITY OF HIGH SLOPE OF RIGHT BANK OF ZAOSHI HYDROPOWER PROJECT，HUNAN PROVINCE

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2007, 26 (S2): -4452 doi:
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[PDF 293 KB] (552)

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The height of the excavated slope on the right bank of Zaoshi hydropower project reaches 110 m. Before the excavation, the deformation and failure were forecasted according to the geologic structure and numerical modeling. The slope is composed of Devonian sandstone and Silurian shale. The strike direction of the stratum is almost perpendicular to the river，which is favorable to the slope stability. But three sets of discontinuities could compose some blocks and cause local instability. In the early stage of excavation above 146 m of the right abutment，some fissures and deformation occurred. So the reinforcement by pre-stressed cables and the drainage tunnel at different altitudes were then performed following the excavation. The monitoring system is in function during and after the excavation，showing that the treatment is effective.

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STUDY ON STABILITY OF HIGH SLOPE OF RIGHT BANK OF ZAOSHI HYDROPOWER PROJECT，HUNAN PROVINCE

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2007, 26 (S2): -4453 doi:
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[PDF 293 KB] (629)

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The height of the excavated slope on the right bank of Zaoshi hydropower project reaches 110 m. Before the excavation, the deformation and failure were forecasted according to the geologic structure and numerical modeling. The slope is composed of Devonian sandstone and Silurian shale. The strike direction of the stratum is almost perpendicular to the river，which is favorable to the slope stability. But three sets of discontinuities could compose some blocks and cause local instability. In the early stage of excavation above 146 m of the right abutment，some fissures and deformation occurred. So the reinforcement by pre-stressed cables and the drainage tunnel at different altitudes were then performed following the excavation. The monitoring system is in function during and after the excavation，showing that the treatment is effective.

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RESEARCH ON DEFORMATION AND FAILURE MECHANISM OF MODERATE-DIP CATACLINAL HARDROCK SLOPE

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2007, 26 (S2): -4458 doi:
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[PDF 324 KB] (819)

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Due to the trend of road paralleling to the axis of the folds，cataclinal slopes are abundant in Hurong Highway in Hubei Province. Of all these cataclinal slopes，the moderate-dip cataclinal hardrock slopes with the bedding plane dip angles ranging between 20° to 60° account for 30 percent，so the stability and treatment are very important to highway construction. Aiming at these problems，this paper presents the character of landform and engineering geology of these types of slopes，and the deformation characterization and sliding process are also analyzed by means of deformation monitoring. Based on the works，the failure mechanism of this type of slope is studied. The result indicates that the penetrative discontinuities have expanded intensely because of weathering，corrosion，tectonic effect and gravity for a long time，and are filled with mud in a certain depth，and thus its shear strength reduces，which is the dominate factor leading to sliding of the moderate-dip cataclinal slopes of hardrock. The conclusion may be useful for assessment of stability and treatment of Hurong Highway and similar engineering.

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RESEARCH ON DEFORMATION AND FAILURE MECHANISM OF MODERATE-DIP CATACLINAL HARDROCK SLOPE

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2007, 26 (S2): -4458 doi:
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[PDF 324 KB] (568)

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Show Abstract

Due to the trend of road paralleling to the axis of the folds，cataclinal slopes are abundant in Hurong Highway in Hubei Province. Of all these cataclinal slopes，the moderate-dip cataclinal hardrock slopes with the bedding plane dip angles ranging between 20° to 60° account for 30 percent，so the stability and treatment are very important to highway construction. Aiming at these problems，this paper presents the character of landform and engineering geology of these types of slopes，and the deformation characterization and sliding process are also analyzed by means of deformation monitoring. Based on the works，the failure mechanism of this type of slope is studied. The result indicates that the penetrative discontinuities have expanded intensely because of weathering，corrosion，tectonic effect and gravity for a long time，and are filled with mud in a certain depth，and thus its shear strength reduces，which is the dominate factor leading to sliding of the moderate-dip cataclinal slopes of hardrock. The conclusion may be useful for assessment of stability and treatment of Hurong Highway and similar engineering.

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STUDY ON MONITORING AND SIMULATION OF SUPER-LONG MOUNTAIN TUNNEL LINING

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2007, 26 (S2): -4465 doi:
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[PDF 0 KB] (614)

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In the design notion of new Austrian tunnelling method，the processes of monitoring and measurement are important and indispensable in the tunnel construction. The work and the analysis based on it not only correctly reflect the stability of surrounding rock，but also optimize the tunnel lining structure as well. Therefore the dynamic design and informational construction of tunnel can be realized. In order to master the real-time deformation of surrounding rock and the stress characteristics of tunnel lining，the stress and displacement monitoring have been carried out in a super-long tunnel through the construction period. Based on the stress monitoring，the stress of the tunnel lining structure in different rock classifications has been simulated using finite element software. The validity of the simulation has been performed through the displacement monitoring and then the critical loads have been acquired. The results can be used in guaranteeing the safety of projects，optimizing the parameters，guiding the tunnel monitoring in the future design.

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STUDY ON MONITORING AND SIMULATION OF SUPER-LONG MOUNTAIN TUNNEL LINING

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2007, 26 (S2): -4465 doi:
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[PDF 292 KB] (890)

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In the design notion of new Austrian tunnelling method，the processes of monitoring and measurement are important and indispensable in the tunnel construction. The work and the analysis based on it not only correctly reflect the stability of surrounding rock，but also optimize the tunnel lining structure as well. Therefore the dynamic design and informational construction of tunnel can be realized. In order to master the real-time deformation of surrounding rock and the stress characteristics of tunnel lining，the stress and displacement monitoring have been carried out in a super-long tunnel through the construction period. Based on the stress monitoring，the stress of the tunnel lining structure in different rock classifications has been simulated using finite element software. The validity of the simulation has been performed through the displacement monitoring and then the critical loads have been acquired. The results can be used in guaranteeing the safety of projects，optimizing the parameters，guiding the tunnel monitoring in the future design.

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ENGINEERING CASE OF A DEEP FOUNDATION
PIT SUPPORTING IN BEIJING

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2007, 26 (S2): -4471 doi:
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[PDF 266 KB] (828)

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Based on a deep foundation pit supporting engineering with excavation depth 19.55 m，the ground situation and surroundings as well as engineering geology are analyzed；and a composite support plan combining the soil-nailed wall with pile-anchor system is proposed to make use of their respective advantages. The technique of artificially excavated piles is adopted for the cobble stratum to solve the problems that power drilling brings about. The maximum value of horizontal displacement is only 12.1 mm and the mechanical properties of each support element are all in working consequence. The support result illustrates that the design is reasonable and the displacement of the pit is controlled effectively. Meanwhile，the work is completed 11 days ahead of the construction arrangement，which leaves much time for the following work. The experience is valuable for the similar projects.

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ENGINEERING CASE OF A DEEP FOUNDATION
PIT SUPPORTING IN BEIJING

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2007, 26 (S2): -4471 doi:
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[PDF 266 KB] (618)

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Show Abstract

Based on a deep foundation pit supporting engineering with excavation depth 19.55 m，the ground situation and surroundings as well as engineering geology are analyzed；and a composite support plan combining the soil-nailed wall with pile-anchor system is proposed to make use of their respective advantages. The technique of artificially excavated piles is adopted for the cobble stratum to solve the problems that power drilling brings about. The maximum value of horizontal displacement is only 12.1 mm and the mechanical properties of each support element are all in working consequence. The support result illustrates that the design is reasonable and the displacement of the pit is controlled effectively. Meanwhile，the work is completed 11 days ahead of the construction arrangement，which leaves much time for the following work. The experience is valuable for the similar projects.

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APPLICATION OF REAL-TIME TELEMETRY TECHNOLOGY
TO LANDSLIDE IN TIANCHI FENGJIE OF THREE GORGES
RESERVOIR REGION

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2007, 26 (S2): -4477 doi:
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[PDF 415 KB] (732)

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The landslide monitoring character and development status of landslide monitoring techniques are introduced. The application of wireless real-time telemetry system in landslide monitoring is summarized. The principle of KLA-1 earth surface displacement telemetry system is expatiated，and the application of this system in landslide monitoring in Tianchi Fengjie of Three Gorges Reservoir region is depicted in detail. The KLA-1 is an apparatus to measure the relative displacement of the surface，which has been used to monitor the displacement of landslides in Maoping，Yichang，and Pipaping，Wanzhou，Chongqing. The system consists of three major components，namely displacement sensing devices，data acquisition and launch module，data receiving and processing terminal. In actual monitoring process，when the landslide moves，there is linear displacement between monitoring point and fixed-point. The information is recorded by angular displacement sensor and converted into corresponding electrical data. The electrical data then are launched by the wireless transmitter module through GSM network to remote terminals，and PC as a terminal receive and the data are analyzed through corresponding monitoring software. According to data analysis，the relationship between displacement of landslide and time is obtained；the developing trend of this landslide is predicted. The veracity and real time of the monitoring device is proven，and the high practical value of this monitoring technology used to monitor landslide is indicated.

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APPLICATION OF REAL-TIME TELEMETRY TECHNOLOGY
TO LANDSLIDE IN TIANCHI FENGJIE OF THREE GORGES
RESERVOIR REGION

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2007, 26 (S2): -4477 doi:
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[PDF 415 KB] (733)

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The landslide monitoring character and development status of landslide monitoring techniques are introduced. The application of wireless real-time telemetry system in landslide monitoring is summarized. The principle of KLA-1 earth surface displacement telemetry system is expatiated，and the application of this system in landslide monitoring in Tianchi Fengjie of Three Gorges Reservoir region is depicted in detail. The KLA-1 is an apparatus to measure the relative displacement of the surface，which has been used to monitor the displacement of landslides in Maoping，Yichang，and Pipaping，Wanzhou，Chongqing. The system consists of three major components，namely displacement sensing devices，data acquisition and launch module，data receiving and processing terminal. In actual monitoring process，when the landslide moves，there is linear displacement between monitoring point and fixed-point. The information is recorded by angular displacement sensor and converted into corresponding electrical data. The electrical data then are launched by the wireless transmitter module through GSM network to remote terminals，and PC as a terminal receive and the data are analyzed through corresponding monitoring software. According to data analysis，the relationship between displacement of landslide and time is obtained；the developing trend of this landslide is predicted. The veracity and real time of the monitoring device is proven，and the high practical value of this monitoring technology used to monitor landslide is indicated.

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DEFORMATION AND FAILURE MECHANISMS OF RESERVOIR LANDSLIDE CONSIDERING FLUID-SOLID COUPLING EFFECT

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2007, 26 (S2): -4484 doi:
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[PDF 294 KB] (561)

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Three are limitations in comprehension of reservoir landslide deformation and failure under conditions of water level decreasing. Traditionally，stress-deformation and stability analysis are based on results from seepage calculations in terms of pore water pressure treatment，and without taking into account the excess pore water pressure around slip-band zone for sluicing. Therefore，the unpractical deformation analysis and stability are obtained，which result in mistake understanding of mechanism of landslide failure. Taking the front part of Huangtupo landslide as an engineering example，the fluid-solid coupling numerical analysis is carried out under conditions of water level decreasing. The stress field，deformation field and pore water pressure field are obtained so as to probe into deformation and failure mechanism of landslide considering the double-field coupling effect. Moreover，the stability varying trends with time is obtained. Study shows that the excess pore water pressure resulting from sluicing is a significant factor inducing deformation and failure of landslide.

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DEFORMATION AND FAILURE MECHANISMS OF RESERVOIR LANDSLIDE CONSIDERING FLUID-SOLID COUPLING EFFECT

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2007, 26 (S2): -4484 doi:
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[PDF 294 KB] (655)

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Show Abstract

Three are limitations in comprehension of reservoir landslide deformation and failure under conditions of water level decreasing. Traditionally，stress-deformation and stability analysis are based on results from seepage calculations in terms of pore water pressure treatment，and without taking into account the excess pore water pressure around slip-band zone for sluicing. Therefore，the unpractical deformation analysis and stability are obtained，which result in mistake understanding of mechanism of landslide failure. Taking the front part of Huangtupo landslide as an engineering example，the fluid-solid coupling numerical analysis is carried out under conditions of water level decreasing. The stress field，deformation field and pore water pressure field are obtained so as to probe into deformation and failure mechanism of landslide considering the double-field coupling effect. Moreover，the stability varying trends with time is obtained. Study shows that the excess pore water pressure resulting from sluicing is a significant factor inducing deformation and failure of landslide.

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REAPPRAISAL OF CONSOLIDATION PARAMETER USING BACK ANALYSIS

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2007, 26 (S2): -4490 doi:
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[PDF 290 KB] (637)

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The purpose is to estimate settlement using the measurement data and to verify the application of back analysis by finite element analysis. It is very important to predict settlement in pre-loading method used to improve soft ground. But the settlement measured in the field shows a considerable difference from the predicted settlement due to various factors such as non-homogeneous soft layers，sampling disturbance，erroneous selection of soil parameters and deficiency of consolidation theories among others. Therefore，analysis of actual settlement behavior based on the measurement data during consolidation period is a very useful procedure in evaluating the rates of consolidation settlement. This study estimates settlement using analysis methods such as Hyperbolic，Hoshino and Asaoka method. Because these prediction methods of ultimate primary settlement are analytically simple and economical，they are widely used in the field construction. But these methods can not predict settlement at the phase of design. To search consolidation parameter for site，back analysis technique was performed using finite element analysis. From the results of analysis，the back-analysis technique for consolidation parameter is verified.

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REAPPRAISAL OF CONSOLIDATION PARAMETER USING BACK ANALYSIS

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2007, 26 (S2): -4490 doi:
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[PDF 290 KB] (601)

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The purpose is to estimate settlement using the measurement data and to verify the application of back analysis by finite element analysis. It is very important to predict settlement in pre-loading method used to improve soft ground. But the settlement measured in the field shows a considerable difference from the predicted settlement due to various factors such as non-homogeneous soft layers，sampling disturbance，erroneous selection of soil parameters and deficiency of consolidation theories among others. Therefore，analysis of actual settlement behavior based on the measurement data during consolidation period is a very useful procedure in evaluating the rates of consolidation settlement. This study estimates settlement using analysis methods such as Hyperbolic，Hoshino and Asaoka method. Because these prediction methods of ultimate primary settlement are analytically simple and economical，they are widely used in the field construction. But these methods can not predict settlement at the phase of design. To search consolidation parameter for site，back analysis technique was performed using finite element analysis. From the results of analysis，the back-analysis technique for consolidation parameter is verified.

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NEW METHOD FOR CHECKING COMPACTNESS OF SOIL-ROCK MIXTURE SUBGRADE BASED ON STATIC LOAD TEST

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2007, 26 (S2): -4496 doi:
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[PDF 377 KB] (670)

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Some limitations and insufficiencies still could be found in the detection methods used to check compactness of filled subgrade，so a new method is put forward. Firstly，in view of the characteristic that the solid(soil and rock) volume will not change in the soil-rock mixture subgrade when it is loaded，a model which describes the change of porosity in the soil-rock mixture subgrade is established，moreover，the changing regularity of the deformation modulus of soil-rock mixture subgrade is also deduced. Then，the soil-rock mixture subgrade is regarded as a semi-infinite elastic space，and the changing regularity of its deformation modulus under the action of load is taken into account. A method for calculating the deformation or settlement of soil-rock mixture subgrade under the vertical surface load is brought forward based on Boussinesq¢s solution by adopting the idea of step loadings. Afterwards，the relationship between the initial porosity ratio of soil-rock mixture subgrade and load-displacement curves is established，and the new method for detecting the compactness of soil-rock mixture subgrade is set up based on static load test curves. Finally，the site test data are fitted based on the theory. The analysis shows that the results of the new method are close to those of the conventional indicating the feasibility and rationality of the new method.

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NEW METHOD FOR CHECKING COMPACTNESS OF SOIL-ROCK MIXTURE SUBGRADE BASED ON STATIC LOAD TEST

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2007, 26 (S2): -4498 doi:
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[PDF 377 KB] (678)

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Some limitations and insufficiencies still could be found in the detection methods used to check compactness of filled subgrade，so a new method is put forward. Firstly，in view of the characteristic that the solid(soil and rock) volume will not change in the soil-rock mixture subgrade when it is loaded，a model which describes the change of porosity in the soil-rock mixture subgrade is established，moreover，the changing regularity of the deformation modulus of soil-rock mixture subgrade is also deduced. Then，the soil-rock mixture subgrade is regarded as a semi-infinite elastic space，and the changing regularity of its deformation modulus under the action of load is taken into account. A method for calculating the deformation or settlement of soil-rock mixture subgrade under the vertical surface load is brought forward based on Boussinesq¢s solution by adopting the idea of step loadings. Afterwards，the relationship between the initial porosity ratio of soil-rock mixture subgrade and load-displacement curves is established，and the new method for detecting the compactness of soil-rock mixture subgrade is set up based on static load test curves. Finally，the site test data are fitted based on the theory. The analysis shows that the results of the new method are close to those of the conventional indicating the feasibility and rationality of the new method.

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APPLICATION OF SEEPAGE BACK ANALYSIS TO ENGINEERING DESIGN

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2007, 26 (S2): -4503 doi:
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[PDF 375 KB] (549)

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Mengkuang Dam in Malaysia has a foundation filled with residual soil of weathered granite. The exploration indicates that the permeability index for dam foundation has great dispersion，drawing the conclusion that the dam foundation soil has small permeability and anti-seepage treatment is not required. However，seepage appears during the reservoir operation. After the project upgrading，it is difficult to make assessment on foundation permeability only based on the results from field test. In this article，inversion analysis is conducted to ascertain the permeability coefficient for dam body and foundation based on the measured data. Through the analysis，permeability indices for dam body and foundation conforming to the observation are obtained，providing main basis for engineering design and showing the reason for dispersion of exploration result. Parameters from inversion analysis are used for permeability prediction and assessment on dam seepage quantity and dam foundation seepage stability after upgrading，drawing the conclusion that the dam seepage quantity after upgrading is large. The requirement for dam foundation seepage stability can not be satisfied and anti-seepage treatment is required. With respect to the real situation of the project，the anti-seepage scheme is proposed.

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APPLICATION OF SEEPAGE BACK ANALYSIS TO ENGINEERING DESIGN

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2007, 26 (S2): -4503 doi:
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[PDF 375 KB] (863)

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Mengkuang Dam in Malaysia has a foundation filled with residual soil of weathered granite. The exploration indicates that the permeability index for dam foundation has great dispersion，drawing the conclusion that the dam foundation soil has small permeability and anti-seepage treatment is not required. However，seepage appears during the reservoir operation. After the project upgrading，it is difficult to make assessment on foundation permeability only based on the results from field test. In this article，inversion analysis is conducted to ascertain the permeability coefficient for dam body and foundation based on the measured data. Through the analysis，permeability indices for dam body and foundation conforming to the observation are obtained，providing main basis for engineering design and showing the reason for dispersion of exploration result. Parameters from inversion analysis are used for permeability prediction and assessment on dam seepage quantity and dam foundation seepage stability after upgrading，drawing the conclusion that the dam seepage quantity after upgrading is large. The requirement for dam foundation seepage stability can not be satisfied and anti-seepage treatment is required. With respect to the real situation of the project，the anti-seepage scheme is proposed.

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DISCUSSION ON STRENGTH REDUCTION METHOD FOR GRAVITY DAM STABILITY ANALYSIS AGAINST SLIDING AND ITS APPLICATION

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2007, 26 (S2): -4510 doi:
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[PDF 299 KB] (473)

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Based on two typical dam foundation models of gravity dams，the stability of the dam against sliding is analyzed by finite difference strength reduction method. The results obtained by this method are compared with those obtained by general Sarma¢s method；and they accord with each other well. It shows that the strength reduction method is applicable to the gravity dam stability analysis against sliding. Two criteria that identifying the limit state of strength reduction method are presented and compared. Results show that for the polygonal sliding surface，the criterion that determines whether or not the localized plastic zone breaks through completely is quite conservative，however，the criterion that identifies whether or not the displacement of the key point on the slip surface changes abruptly may give a perfect result，which is accordance with that obtained by limit equilibrium method.

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DISCUSSION ON STRENGTH REDUCTION METHOD FOR GRAVITY DAM STABILITY ANALYSIS AGAINST SLIDING AND ITS APPLICATION

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2007, 26 (S2): -4510 doi:
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[PDF 299 KB] (810)

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Based on two typical dam foundation models of gravity dams，the stability of the dam against sliding is analyzed by finite difference strength reduction method. The results obtained by this method are compared with those obtained by general Sarma¢s method；and they accord with each other well. It shows that the strength reduction method is applicable to the gravity dam stability analysis against sliding. Two criteria that identifying the limit state of strength reduction method are presented and compared. Results show that for the polygonal sliding surface，the criterion that determines whether or not the localized plastic zone breaks through completely is quite conservative，however，the criterion that identifies whether or not the displacement of the key point on the slip surface changes abruptly may give a perfect result，which is accordance with that obtained by limit equilibrium method.

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ANALYSIS OF THERMAL STATE OF PERMAFROST UNDER HIGH EMBANKMENT ALONG QINGHAI—TIBET RAILWAY

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2007, 26 (S2): -4518 doi:
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[PDF 321 KB] (1130)

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Thermal state of permafrost under high embankment along Qinghai—Tibet Railway is monitored and studied. Three monitoring profiles with different embankment heights(3.0，4.2 and 5.0 m) in the Beiluhe test site are chosen to analyze the characters of ground temperature under the embankment. The in-situ monitoring results show that the reasonable embankment height has positive effects on frozen soil protection and can promote the rise of permafrost table under the embankment. The permafrost tables under the three embankments have 0.3–0.7 m rise after two freezing-thawing circles. But the engineering effect does not increase linearly with the embankment height. The embankment with a height of 3.0 m has better engineering effects that those with heights of 4.2 m and 5.0 m according to the analysis. To ensure the thermal stability of the roadbed，the reasonable embankment height must be met. The analytical results also indicate that the high embankment has potential disadvantages. The thawing process of the embankment surface is longer while the freezing process is shorter than that of the natural surface. The embankment surface temperature，which is similar with that of natural surface in freezing process，is higher in thawing process. The consequence is that the thawing exponential of embankment surface is greater while the freezing exponential is smaller than that of the natural surface. At the same time，the conduction of cold energy in cold semi-year as well as heat energy in warm semi-year is held back because of temperature resistance of embankment material，which causes the ground temperature below the permafrost table to increase for sustaining the rise of the permafrost table. These disadvantages may affect the long-term stability of the permafrost under the embankment. Analysis of the observation data indicates that the engineering thermal disturbance depth of high embankment to the permafrost is about 10.0 m.

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ANALYSIS OF THERMAL STATE OF PERMAFROST UNDER HIGH EMBANKMENT ALONG QINGHAI—TIBET RAILWAY

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2007, 26 (S2): -4518 doi:
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[PDF 321 KB] (652)

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Thermal state of permafrost under high embankment along Qinghai—Tibet Railway is monitored and studied. Three monitoring profiles with different embankment heights(3.0，4.2 and 5.0 m) in the Beiluhe test site are chosen to analyze the characters of ground temperature under the embankment. The in-situ monitoring results show that the reasonable embankment height has positive effects on frozen soil protection and can promote the rise of permafrost table under the embankment. The permafrost tables under the three embankments have 0.3–0.7 m rise after two freezing-thawing circles. But the engineering effect does not increase linearly with the embankment height. The embankment with a height of 3.0 m has better engineering effects that those with heights of 4.2 m and 5.0 m according to the analysis. To ensure the thermal stability of the roadbed，the reasonable embankment height must be met. The analytical results also indicate that the high embankment has potential disadvantages. The thawing process of the embankment surface is longer while the freezing process is shorter than that of the natural surface. The embankment surface temperature，which is similar with that of natural surface in freezing process，is higher in thawing process. The consequence is that the thawing exponential of embankment surface is greater while the freezing exponential is smaller than that of the natural surface. At the same time，the conduction of cold energy in cold semi-year as well as heat energy in warm semi-year is held back because of temperature resistance of embankment material，which causes the ground temperature below the permafrost table to increase for sustaining the rise of the permafrost table. These disadvantages may affect the long-term stability of the permafrost under the embankment. Analysis of the observation data indicates that the engineering thermal disturbance depth of high embankment to the permafrost is about 10.0 m.

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STUDY ON EFFECT OF GEOELECTRIC FIELD ON CONVECTION HEAT TRANSFER PROPERTIES IN FRACTURED ROCK BLOCK

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2007, 26 (S2): -4525 doi:
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[PDF 311 KB] (451)

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According to the properties that the convection heat transfer in fractured rock block is affected by geoelectric field in the process of in-situ leaching，the model of convection heat transfer under geoelectric field has been brought out；and the influences have been investigated through the experiments. The following results can be drawn. (1) The geoelectric field affects the properties of convection heat transfer obviously；and the influential degree is related with the heat flux，the seepage velocity of liquid，the characters of liquid and so on. (2) The convection heat transfer coefficient increases with the increase of forward electric field voltage，and decreases with the increase of the reversed one. (3) Under the action of geoelectric field，the variation amplitude of convection heat transfer coefficient with low heat flux is evidently higher than that with high heat flux. (4) The effect of the geoelectric field on the convection heat transfer in fractured rock block is weakened gradually with the increase of the seepage velocity of liquid. (5) The higher the mineralization of solution in fractured rock block is，the greater the influence of geoelectric field on the convection heat transfer is.

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STUDY ON EFFECT OF GEOELECTRIC FIELD ON CONVECTION HEAT TRANSFER PROPERTIES IN FRACTURED ROCK BLOCK

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2007, 26 (S2): -4525 doi:
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[PDF 311 KB] (638)

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According to the properties that the convection heat transfer in fractured rock block is affected by geoelectric field in the process of in-situ leaching，the model of convection heat transfer under geoelectric field has been brought out；and the influences have been investigated through the experiments. The following results can be drawn. (1) The geoelectric field affects the properties of convection heat transfer obviously；and the influential degree is related with the heat flux，the seepage velocity of liquid，the characters of liquid and so on. (2) The convection heat transfer coefficient increases with the increase of forward electric field voltage，and decreases with the increase of the reversed one. (3) Under the action of geoelectric field，the variation amplitude of convection heat transfer coefficient with low heat flux is evidently higher than that with high heat flux. (4) The effect of the geoelectric field on the convection heat transfer in fractured rock block is weakened gradually with the increase of the seepage velocity of liquid. (5) The higher the mineralization of solution in fractured rock block is，the greater the influence of geoelectric field on the convection heat transfer is.

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MONITORING AND ANALYSIS OF COMPOSITE FOUNDATION REINFORCED BY T-SHAPED BIDIRECTIONAL SOIL-CEMENT DEEP MIXING PILE UNDER EMBANKMENT LOADS

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2007, 26 (S2): -4530 doi:
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[PDF 0 KB] (767)

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With the engineering problems of traditional deep mixing techniques in China，a new T-shaped bidirectional deep mixing technique is introduced. The settlement，layered settlement，lateral deformation，excess pore water pressure and earth pressure of foundation reinforced by T-shaped bidirectional soil-cement deep mixing pile are analyzed under embankment loads. The wide application and economic benefit of T-shaped bidirectional soil-cement deep mixing pile are discussed.

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MONITORING AND ANALYSIS OF COMPOSITE FOUNDATION REINFORCED BY T-SHAPED BIDIRECTIONAL SOIL-CEMENT DEEP MIXING PILE UNDER EMBANKMENT LOADS

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2007, 26 (S2): -4530 doi:
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[PDF 364 KB] (1057)

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With the engineering problems of traditional deep mixing techniques in China，a new T-shaped bidirectional deep mixing technique is introduced. The settlement，layered settlement，lateral deformation，excess pore water pressure and earth pressure of foundation reinforced by T-shaped bidirectional soil-cement deep mixing pile are analyzed under embankment loads. The wide application and economic benefit of T-shaped bidirectional soil-cement deep mixing pile are discussed.

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ENGINEERING CASE ANALYSIS OF EMBANKMENT REINFORCED BY ANCHOR CABLE ANTI-SLIDING PILE

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2007, 26 (S2): -4538 doi:
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[PDF 404 KB] (526)

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Great subsidence and lateral displacement take place in the embankment of Ningbo—TaizhouWenzhou expressway during construction；and embankment presents some initial signs of landslide. In order to improve the stability of embankment against sliding in the section，the anti-sliding piles with prestressed anchor cable which combines some bored pile with prestressed anchor cable are set to control the subsidence and lateral displacement of embankment. At the same time，the monitoring of displacement and stability are carried out. All the observation data are acquired through monitoring the stress and displacement of anti-sliding pile with prestressed anchor cable，in turn this result can control and guide the construction of embankment. Combining actual monitoring data analysis of this project，the reinforcement mechanism and effect of the method to reinforce the embankment using anti-sliding pile with prestressed anchor cable are evaluated；and several qissues and advices for this measurement are presented，which can provide references to similar engineering.

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ENGINEERING CASE ANALYSIS OF EMBANKMENT REINFORCED BY ANCHOR CABLE ANTI-SLIDING PILE

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2007, 26 (S2): -4538 doi:
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[PDF 404 KB] (689)

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Great subsidence and lateral displacement take place in the embankment of Ningbo—TaizhouWenzhou expressway during construction；and embankment presents some initial signs of landslide. In order to improve the stability of embankment against sliding in the section，the anti-sliding piles with prestressed anchor cable which combines some bored pile with prestressed anchor cable are set to control the subsidence and lateral displacement of embankment. At the same time，the monitoring of displacement and stability are carried out. All the observation data are acquired through monitoring the stress and displacement of anti-sliding pile with prestressed anchor cable，in turn this result can control and guide the construction of embankment. Combining actual monitoring data analysis of this project，the reinforcement mechanism and effect of the method to reinforce the embankment using anti-sliding pile with prestressed anchor cable are evaluated；and several qissues and advices for this measurement are presented，which can provide references to similar engineering.

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CASE OF AN UNSTABLE ROCK SLOPE REINFORCEMENT

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2007, 26 (S2): -4545 doi:
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[PDF 345 KB] (823)

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The main work of a project is the state key one. The rock slope is unstable during the construction process and threatens the safety of lower structures and workers. According to the environment and the concrete geological conditions，the comprehensive reinforcement method of prestressed anchor cable，self-drilling anchor bolt，steel-net and shotcrete is adopted for the slope using the engineering analogism and experiential method. Rational design parameters，reasonable reinforcement structure form and scientific construction process ensure the reinforcement measures to play roles fully. Based on the crack location surveyed during drilling hole and slope limit equilibrium theory，the mechanical parameters of rock are obtained by inverse calculation method. Then the safety factor of the reinforced slope is gained. Results show that the safety factor increases largely，which ensures the safety and the subsequent construction. The design and construction of the reinforced rock slope are introduced in detail.

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CASE OF AN UNSTABLE ROCK SLOPE REINFORCEMENT

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2007, 26 (S2): -4545 doi:
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[PDF 345 KB] (749)

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The main work of a project is the state key one. The rock slope is unstable during the construction process and threatens the safety of lower structures and workers. According to the environment and the concrete geological conditions，the comprehensive reinforcement method of prestressed anchor cable，self-drilling anchor bolt，steel-net and shotcrete is adopted for the slope using the engineering analogism and experiential method. Rational design parameters，reasonable reinforcement structure form and scientific construction process ensure the reinforcement measures to play roles fully. Based on the crack location surveyed during drilling hole and slope limit equilibrium theory，the mechanical parameters of rock are obtained by inverse calculation method. Then the safety factor of the reinforced slope is gained. Results show that the safety factor increases largely，which ensures the safety and the subsequent construction. The design and construction of the reinforced rock slope are introduced in detail.

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EXPERIMENTAL STUDY ON RHEOLOGICAL MECHANICAL PROPERTIES OF SHALE UNDER UNLOADING CONDITION

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2007, 26 (S2): -4552 doi:
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[PDF 247 KB] (971)

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The deformation of rock mass takes on time-dependent effect after its excavation；and the instaneous mechanical and rheological mechanical responses of rock mass vary greatly in some degree. At present，the research on this rheological behaviour is mostly based on loading conceptual rock rheological test. However，researches on the rheological property under unloading stress path are seldom taken into account. Thus，the results sometimes cannot coincide with the practical mechanical process. The fresh shale sample in underground powerhouse of Pengshui Hydropower Station are taken to carry out unloading rheological test under the stress conditions of constant axial stress and gradually unloading lateral stress so as to preliminarily study its triaxial unloading rheological property. Experimental research reveals that the axial and lateral creep curves of shale specimens behave the attenuation creep stage under relatively low stress state. The rheological constitutive equation is obtained by means of parameters regression of H-K three-component model. Research reveals that the H-K three-component model can well present the unloading rheological behaviour under this stress state.

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EXPERIMENTAL STUDY ON RHEOLOGICAL MECHANICAL PROPERTIES OF SHALE UNDER UNLOADING CONDITION

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2007, 26 (S2): -4552 doi:
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[PDF 247 KB] (371)

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The deformation of rock mass takes on time-dependent effect after its excavation；and the instaneous mechanical and rheological mechanical responses of rock mass vary greatly in some degree. At present，the research on this rheological behaviour is mostly based on loading conceptual rock rheological test. However，researches on the rheological property under unloading stress path are seldom taken into account. Thus，the results sometimes cannot coincide with the practical mechanical process. The fresh shale sample in underground powerhouse of Pengshui Hydropower Station are taken to carry out unloading rheological test under the stress conditions of constant axial stress and gradually unloading lateral stress so as to preliminarily study its triaxial unloading rheological property. Experimental research reveals that the axial and lateral creep curves of shale specimens behave the attenuation creep stage under relatively low stress state. The rheological constitutive equation is obtained by means of parameters regression of H-K three-component model. Research reveals that the H-K three-component model can well present the unloading rheological behaviour under this stress state.