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2007, 26 (08): -0 doi:
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RIGOROUS AND QUASI-RIGOROUS LIMIT EQUILIBRIUM SOLUTIONS OF 3D SLOPE STABILITY AND APPLICATION TO ENGINEERING

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2007, 26 (08): -1513 doi:
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The rigorous and quasi-rigorous limit equilibrium solutions to 3D slope stability，which satisfy six and five equilibrium conditions respectively，are derived. Firstly，the normal stress distribution over the 3D slip surface is initially assumed，which is modified by a function with five parameters involved for the rigorous solution，or by a function with four parameters involved for the quasi-rigorous solution. The rigorous equilibrium equations are reduced to a sixth-order algebraic equation with respect to the 3D factor of safety；and adjustments of slip direction and rotational coefficient are needed for positive values of normal stresses over the slip surface. The quasi-rigorous equilibrium equations are reduced to a quartic equation with respect to the 3D factor of safety，the maximum real root of which is the quasi-rigorous solution. Only adjustment of slip direction is needed for quasi-rigorous solution；and the computation process is much simpler than that of rigorous solution. The results of example studies show that the difference between the rigorous and quasi-rigorous solutions is negligible；and the latter is thus more applicable to the practical engineering. The presented method features simple principle and high precision，accommodates generalized shape of 3D slip surface，and can be readily implemented into computer. This method has been used in the stability analysis of the abutment slope on the left bank of Yinpan Hydropower Station on Wujiang River，assisting in the design of abutment and stabilization measures.

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A RIGOROUS THREE-DIMENSIONAL LIMIT EQUILIBRIUM METHOD

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2007, 26 (08): -1529 doi:
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Up to now，there is no three-dimensional limit equilibrium method that is able to satisfy all six equilibrium conditions. While formulating the equilibrium conditions，the whole sliding body is taken as the loaded object. By means of remedy of the total normal pressures acting on the slip surface，a rigorous limit equilibrium method for the three-dimensional stability analysis of slope is realized，which satisfies all the six equilibrium conditions and accommodates to slip surfaces of any shape. The system of equations herein formulated enjoys excellent numerical properties. Its Newton method is independent of the choice of the initial iteration values. The existence of solution is proved theoretically. In case of internal friction angle j = 0°，moreover，that the solution is unique is also proved；and an explicit expression for safety factor is given. Meanwhile，in order to simplify the preprocessing and to improve the precision of the analysis，the volume integrals over the sliding body are transformed into the boundary integrals. The division of the sliding body is accordingly unnecessary.

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SHAKING TABLE TEST ON METRO STATION STRUCTURE AND 3D NUMERICAL SIMULATION OF SEISMIC RESPONSE

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2007, 26 (08): -1538 doi:
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The shaking table test on typical metro station structure is simulated by FLAC3D. The calculation model includes the following four aspects. (1) The calculation area is identical with the model box. (2) The Davidenkov model is employed to simulate the dynamic nonlinear characteristics of model soil；and the structural model is regarded as in elastic state during test. (3) The dynamic boundary conditions are set as acceleration boundaries because the deformation of model box can be neglected. (4) The seismic loads accord with the waves used in the test. The test and calculation results include the rules of acceleration response of model soil and metro station structure model，the dynamic strain of metro station structure model and the dynamic soil pressure between model soil and structure model. The calculation results agree well with the test results，which shows the rationality of the proposed model. It can be used to simulate the dynamic characteristics of model soil，calculate the dynamic response of metro station structure and analyze the dynamic interaction between soil and structure. The study provides foundations to establish the 3D calculation method for metro station structure under seismic load in soft soil areas.

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DISCUSSION ON THREE CHARACTERISTIC FOCAL DEPTHS OF MINING-INDUCED SEISMICITY

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2007, 26 (08): -1546 doi:
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In the current study，three characteristic focal depths of mining-induced seismicity in coalmines，i.e. initiation depth，roof upper-bound depth，and floor lower-bound influence depth，are identified from field microseismic monitoring data. These characteristic depths depend on the relative distance between the hypocenter of a seismic event and ground surface or the location of the roof and floor of the coal seam. The initiation depth is the one beyond which rockbursts will happen. The roof upper-bound depth is defined as the depth of the seismic events located above the roof whose magnitudes are greater than certain thresholds；and the floor lower-bound influence depth is defined as the difference between the depth of the observed maximum seismic event below the floor and the depth of the floor. The mechanisms of the characteristic focal depths are also discussed. The initiation depth is explained by a power law model considering coal strength and the stress acting on the coal body，the roof upper-bound depth is explained by a bending model of a thick plate or beam；and the floor lower-bound influence depth is explained by the combined effect of elastic rebound due to unloading and the effect of Poisson¢s ratio as well as the influence of active faults. Finally，the impact of understanding the characteristic focal depths on mining safety is discussed. It is expected that a better understanding of these characteristic depths will facilitate the mitigation and control of mining-induced seismic hazards in underground coalmines.

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DEVELOPMENT STATE OF CHINESE JOURNAL OF ROCK MECHANICS AND ENGINEERING IN RECENT YEARS

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2007, 26 (08): -1553 doi:
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The Chinese Journal of Rock Mechanics and Engineering(CJRME) started in 1982，which was founded by Professor TAN Tjongkie. With the over twenty-five years¢ developments，the various indices of CJRME occupied front ranks among the journals of rock mechanics and geotechnical engineering. However，some problems and shortcomings are encountered during the development of CJRME，even some are serious that are deserved the deep considerations for scholars and operators. Those lessons mentioned above will excite and prompt the attentions of the relative readers，scholars and the people in geotechnical engineering to understand the future developments and tread of CJRME. In order to create a perfect atmosphere，some explorations for the journal are discussed. Based on the conceptions of development of CJRME，the achievements and shortages in the development from 2001 to 2006 will be discussed，which will set a solid basis for its development. The EI-indexed information，paper constitution，and the specific characteristics of CJRME，the future development and various indices are analyzed. During the operation and reformation procedures of CJRME，the effects are obvious when some necessary measures have been taken；and the tenet of journal management is properly implemented. The idea of journal management is intensified and all possible efforts are taken to develop CJRME to be a first-class in China and world-known selected journal.

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DESIGN OF FUEL TANK FOUNDATIONS ON SOFT CLAY DEPOSIT

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2007, 26 (08): -1561 doi:
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A foundation design method and considerations for two large-sized fuel tanks on soft marine clay deposit in Attawapiskat，located in the James Bay coastal area of Northern Ontario，Canada are describes. The tanks with diameter of 29 m and height of 12 m are required for fuel supply for a diamond mine，located approximately 100 km west of Attawapiskat. Each tank has a volume capacity of 7.5 million litres；and the maximum tank pressure of 140 kPa is exerted. The design involving a mat foundation is introduced. The design criteria require adequate safety margin against potential failure(bearing pressure and edge pressure) and relatively stringent settlement(differential) limits. Other design considerations include frost effects，limited availability of granular and rockfill materials，short construction period，and spill containment. Stability assessment indicates the edge failure to be more critical than the bearing capacity failure mode，and emphasizes the need for soil improvement. The uses of geosynthetic reinforcement along the perimeter of the tank and prefabricated vertical drains(PVDs) in the foundation soil in conjunction with site preloading are expected to reinforce the foundation，accelerate consolidation and reduce post-construction settlement. The design studies confirm the feasibility of constructing a mat foundation within short time，provided that the ground improvement measures mentioned above were incorporated.

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EXPERIMENTAL STUDY ON DEFORMATION AND STRENGTH PROPERTIES OF COARSE MARBLE WITH DISCONTINUOUS PRE-EXISTING CRACKS UNDER DIFFERENT CONFINING PRESSURES

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2007, 26 (08): -1572 doi:
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Experiments were carried out to study coarse marble with discontinuous pre-existing cracks under conventional triaxial compression by the MTS815.03 rock mechanics servo-controlled testing machine. Based on the experimental results，the deformation and strength properties of coarse marble with discontinuous pre-existing cracks under different confining pressures were investigated. The results show that the deformation of intact rock specimens and marble with discontinuous pre-existing cracks after peak strength changes from strain softening into ideal plasticity. The sensitivity of peak circumferential strain to the confining pressure is higher than that of peak axial strain. The relation between strength and confining pressure can be expressed by Coulomb criterion；what¢s more，the sensitivity of residual strength to the confining pressure is higher than that of peak strength. The coarse marble has greater crystal in size of 4–6 mm. The Young¢s modulus of intact rock specimen increases with the confining pressure；and the peak strain has a positive linear relation with the confining pressure. However，the Young¢s modulus and the peak strain of rock specimen with discontinuous pre-existing cracks have more complex relations with the confining pressure and vary with the crack angles. In uniaxial compression，the peak strength of rock specimen with discontinuous pre-existing cracks has a close relation with the crack angles；and the maximal axial stress depends on the fracture modes between the inner tip of two pre-existing cracks and friction slips between crystals. Under lower confining pressure(s3≤10 MPa)，the triaxial peak strength of rock specimens with discontinuous pre-existing cracks is lower than that of intact rock specimens；but for triaxial residual strength，there are no great differences between intact coarse marble and marble with discontinuous pre-existing cracks. However，under higher confining pressure(s3＞10 MPa)，the triaxial strengths(peak strength and residual strength) of intact rock specimen are approximately same as those of rock specimen with discontinuous pre-existing cracks，which shows that the supporting capacity of coarse marble specimen is only related to the confining pressure but no relation with the distribution of pre-existing cracks. The internal friction force determines the strength property of coarse marble.

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QUANTITATIVE ANALYSIS OF CONCRETE CT IMAGES BASED ON DAMAGE-FRACTURE EVOLUTION THEORY

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2007, 26 (08): -1588 doi:
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The characters of microstructure and crack change in concrete can be investigated by CT images.But now there is rare quantitative analysis of concrete CT images in China. Damage-fracture evolution theory has been applied to the quantitative analysis of concrete CT images. In such a way，the degrees of perfection and damage are used to analyze the strength of each variation，which solves the question that the distribution range of CT numbers is too wide. The transition from microscopic analysis to macroscopic one is accomplished on the basis of l-level perfect field and l-level damage-fracture field. Furthermore，the areas of cracks，aggregates，mortar and air are extracted from CT images according to l1–l2 level intercepted section. Then，the approach to measure the size of each area has been put forward，which has realized the description of each substantial distribution. Based on this method，the application prospect of damage-fracture evolution theory to the experimental study on concrete CT image is discussed.

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EQUAL SAFETY FACTOR METHOD AND ITS RELIABILITY ANALYSIS FOR ROCK FOUNDATION OF DAM

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2007, 26 (08): -1594 doi:
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It is focused on the anti-sliding stability problem for multi-slide surfaces of dam foundation. Firstly，a new method called equal safety factor is presented for multi-slide surfaces or double-slide surfaces mode， which is obtained by modifying the wedge method. Subsequently，the reliability research is conducted by using the limited equation composed of safety factor；and the effects of the cross-correlation among strength parameters frictional coefficient f，cohesion c on the stability index are analyzed through calculations of several typical sections of gravity dam foundation. Finally，the safety check formula of ，its permitted index and the corresponding partial coefficients are proposed. The results indicate that the cross-correlation of strength parameters f and c affect the reliability index remarkably. The reliability index b increases nonlinearly with correlation coefficient when the two parameters change from independent to negative correlated ones；and the largest increment is 48.7%. The parameters f，c are usually treated as independent ones for traditional method，which results in reliable calculation result. A suit of corresponding partial coefficients is also proposed for the design check formula of . The recommended values of structure coefficient are classified to three grades with 1.2，1.1 and 1.0 for concrete dams of grade-I，grade-II and grade-III，respectively. Compared with the traditional wedge method，the new method is stricter for bad foundation and high dams，but looser for good foundation and low dams. Using the approach of equal safety factor for design of dam foundation，the safety degree is equivalent or even more reliable to the traditional method；moreover，the distribution of reliability is more reasonable.

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STATISTICAL DAMAGE MODEL OF CONCRETE UNDER UNIAXIAL TENSION CONSIDERING DYNAMIC STRAIN-RATE EFFECT

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2007, 26 (08): -1603 doi:
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Based on the meso-scale damage mechanism of quasi-brittle materials，the damage can be generalized into two aspects，“the decrease of the effective cross-section”and“the degradation of the elastic modulus of the effective region corresponding to the effective cross-section”，which can be represented by rupture and yield damage modes respectively. The essence of failure process is the continuum accumulation and evolution process of the two damage modes. The dynamic behavior behaved by dry concrete can be essentially attributed to the inertia effect itself，which leads to the change of the breakage form and the two damage evolution process of materials. Ignoring the effect of water viscosity，by the hypothesis that the damage evolution rule of material under different strain-rate cases obeys a certain similarity，an increment-format dynamic damage constitutive model under uniaxial tension is proposed. Comparison of the prediction results with experimental data shows that it can accurately reflect and predict the dynamic damage characteristics in the uniform damage phase for concrete under the constant or variable strain-rate cases. Combining with the examples，the dynamic damage mechanism of materials is discussed from the view points of effective stress，nominal stress and the energy absorption capability. Two characteristic states，the peak nominal stress state and the critical state when appears macro-crack are distinguished；and the latter is proposed as the final failure point in the constitutive model. Treated by this way，not only the ductibility of the uniform damage phase of materials can be considered adequately，but also the size effect of constitutive model during the local breakage phase can be avoided to consider

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STRESS-STRAIN RELATIONSHIPS AND NONLINEAR MOHR STRENGTH CRITERION OF FROZEN SAND CLAY

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2007, 26 (08): -1612 doi:
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A series of triaxial compression tests were carried out on frozen sand clay with confining pressures from 0.0 to 18.0 MPa at －6 ℃. The experimental results indicate that the strain softening exists in the stress-strain relationships of the studied frozen sand clay when the confining pressures is below 3.0 MPa；and the strain hardening phenomenon appears in the stress-strain relationships when confining pressures is greater than 3.0 MPa. Since the general hyperbolic model cannot describe the strain hardening behavior；and Duncan-Chang model cannot describe the strain softening behavior of frozen sand clay；an improved Duncan-Chang model is proposed. This model can describe not only the strain softening behavior but also the strain hardening behavior of frozen sand clay. Moreover，its modeling precision is better than those of Duncan-Chang model and the general hyperbolic model. Due to pressure melting，shear strength of frozen sand clay nonlinearly changes with increasing confining pressures. In order to solve the problem that linear Mohr-Coulomb criteria can not exactly reflect the shear strength of frozen sand clay，a nonlinear Mohr criterion of frozen sand clay is presented. The results calculated by the nonlinear Mohr criterion of frozen sand clay illustrate that it has higher precision and can more exactly describe the shear strength of frozen sand clay than the linear Mohr-Coulomb criterion.

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APPLICATION OF BLOCK THEORY TO SURROUNDING ROCK STABILITY OF UNDERGROUND CAVERNS IN HUANGGOU
PUMPED STORAGE STATION

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2007, 26 (08): -1618 doi:
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The rock mass fracture is considerably developed in underground caverns of Huanggou Pumped Storage Station，so it is significant for engineering construction to predefine whether there are unstable blocks on excavation planes of underground caverns. According to the engineering geological condition of Huanggou Pumped Storage Station and characteristics of plenty of fractures，the block theory，which is an effective engineering analysis method for the stability of fractured rock mass，is adopted to analyze the stability of surrounding rock of underground caverns. Because there are a lot of fractures in the surrounding rock，computing load of the analysis is very large. Thinking about above-mentioned condition，vector analysis method of block theory is adopted to rapidly analyze block by computer. According to the elements of vector analysis method，combining local three-dimensional coordinate of underground caverns，numerical software MATLAB is adopted to compile calculating program applicable to arched underground cavern. The calculating program needs to input joints occurrence，measuring point coordinate，radius of underground caverns，vertical wall height of underground caverns and other relevant engineering data to search for the existent unstable rock blocks in ranges of underground caverns and to analyze the boundary condition，geometric parameter，failure mode and stability factor of each block in turn. So the vertex three-dimensional coordinates，volume，stability factor and other relevant information of key block can be obtained at last. Then CAD is used to show the position and geometrical shape of key block in three-dimensional space. The information can provide guidance for excavation of underground caverns.

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BLOCK-DIVIDING LIMIT EQUILIBRIUM ANALYSIS METHOD WITH MULTIPLE SLIDING-PLANES

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2007, 26 (08): -1625 doi:
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When single-plane sliding block has more than one joint face，double-plane sliding block has more than two joint faces，and the block is above these joint faces，some defections of stability calculation in traditional block theory may occur. So，block-dividing limit equilibrium analysis method is presented. The method divides block along the intersection edge of joint faces and neglects the vertical shear force between dividing-blocks i.e. takes horizontal normal force and shear force into account；as to an assumed sliding direction，by satisfying vertical force equilibrium of every dividing-block and whole force equilibrium in the sliding direction，the factor of stability can be solved. However，the non-equilibrium force in the horizontal direction perpendicular to the assumed sliding direction is always existent, because the block is usually non-symmetrical and the assumed sliding direction is not the practical one. By changing the sliding direction from 0° to 360°，when the non-equilibrium force gets to zero，the solutions satisfy force equilibrium in three othogonal directions；and the actual potential sliding direction can be determined rather than assumed. In this case，the factor of stability is minimum or close to minimum，whose meaning is similar with Pan¢s principle of the maximum and the minimum. The method can solve well the stability analysis of multiple sliding-planes block. By contrasted with traditional block theory，the method is validated；and the continuous change of factor of stability and sliding direction with gradual transition from non-symmetrical double-face sliding to single-face sliding can be interpreted properly. At last，a practical engineering case is studied.

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3D GEOLOGICAL VISUALIZATION AND NUMERICAL MODELING OF COMPLICATED SLOPE

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2007, 26 (08): -1633 doi:
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The construction of the 3D visualization model and the numerical model of rock slope is critical in geotechnical，hydroelectric and hydropower projects. The 3D visualization model not only illustrates the spatial combination of structural plane in slope，but also discloses the macroscopic failure mode of slope. The combination and transition between the visualization model and the numerical model can indicate the simulation and dynamic modification of geological information. Based on AutoCAD platform，AutoLisp program and interpolation method of MLSM are used to generate the 3D visualization model. Moreover，the interface to the numerical model is discussed. This technique well combines the excellent graphic manipulation of AutoCAD and the general numerical softwares FLAC3D and 3DEC of ITASCA Ltd.. Besides，the model can adapt the technique to change the geological information. Combined with the discrete element method for deformable bodies，the technique has been well applied to the water intake high slope in Baihetan Hydropower Station. FISH program in 3DEC and AutoLISP program in AutoCAD are combined to improve the functions of preprocessing and post processing of 3DEC. The anchorage method in 3DEC，visualization of contour chart and nephogram of 3D displacement and plastic zone are discussed.

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RESEARCH ON TRANSMISSION BEHAVIORS OF NONLINEAR JOINTS WITH 2D WAVE PROPAGATION

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2007, 26 (08): -1645 doi:
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Two-dimensional wave propagation through joints is a complicated problem. The important factors influencing the transmissivity of joint include normalized stiffness of joints，ray angle，radial distance，joint parameters，incident wave frequency，etc.. Under help of 3DEC，the propagation of 2D wave through single joint with nonlinear joint model，the rules of transmissivity under different strength parameters and geometric positions are studied. According to the research results of single joints，transmissivity of 2D wave through straight joint interface is not only associated with normal and shear stiffness of joint，but also controlled by the joint strength parameters，cohesion and inner friction angle. Values of joint cohesion and inner friction angle reflect the closure degree of joint，which causes transmissivity to take on different tendencies. If the inner friction angle keeps constant，transmissivity will increase with the increase of cohesion strength until it reaches to a superior limit. While if the cohesion keeps constant，transmissivity is different in response to cohesion. If the cohesion is at a low level，the transmissivity will increase with the increase of inner friction angle until it reaches to a superior limit. However，the transmissivity will initiate at a high value then decrease rapidly to a lower level with the increase of the inner friction angle if the cohesion is at a high level. Finally，calculations of transmissivity under the condition of multiple joints are tentatively conducted according to the single joint research results；and some useful comparison works are achieved in dynamic response under complicated joints distribution.

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PULL-OUT MODEL EXPERIMENT ON FAILURE MECHANISM OF FULL-LENGTH BONDING GLASS FIBER REINFORCED POLYMER REBAR

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2007, 26 (08): -1653 doi:
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The glass fiber reinforced polymer(GFRP) is a new material，which combines with resin matrix and glass fiber. It has some superior characteristics such as high tensile strength，anticorrosion，light deadweight；and the trend using GFRP rebar to replace the reinforced bar in geotechnical engineering is rising year after year. Otherwise，the GFRP rebar is also a new groping applied form. A series of tests on tensile strength，anticorrosion，creep behavior have been carried out for the feasibility of GFRP rebar applied in permanent reinforcement engineering. The failure mechanism of full-length bonding GFRP rebar has been researched by pull-out model experiment. Three rebar models are made in total；and parallel destructive test on the two specimens have been conducted for three times. According to the test phenomenon and analysis results of the test data，rationality of GFRP rebar pull-out test model is affirmed；and the relationship between mortar bulk strength and stress transfer depth of the rebar is explained. The trend of peak value character of GFRP screw rebar¢s shear stress varying with load is presented. Combining with stress distribution characteristics of mortar bulk，the probable failure form and mechanism of GFRP screw rebar have been sufficiently argued. Under high mortar strength，the tensile failure or shear failure may occur. If the axial tensile stress firstly reaches rebar¢s the tensile strength，the tensile failure will occur at the free section；and the shear failure will occur at the anchorage section if the maximal shear stress first achieves fiber yarn¢s shear strength.

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CALCULATION OF IMPACT FORCE OF OUTRUNNER BLOCKS IN DEBRIS FLOW CONSIDERING ELASTOPLASTIC DEFORMATION

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2007, 26 (08): -1664 doi:
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A theoretical method based on Hertz contact theory is presented for calculation of impact force of outrunner block in debris flow. Special attentions are given to the elastoplastic deformation of structures. Hertz contact theory is modified using perfectly elastoplastic Thornton hypothesis to consider the elastoplastic deformation of structures. In the simulation of the impact of outrunner blocks in debris flow and counter structures，the structure is simplified as a still plane and the block is simulated by a particle with a certain velocity. So the impact force can be expressed by a simple function. Based on the modified Hertz contact theory and the simplified simulation of impact，a new method is approved to calculate the impact force of outrunner blocks in debris flow on structures. Based on a limited parametric study，it is shown that the impact causes plastic deformation on concrete structures at a low velocity. The impact force considering the elastoplastic deformation of structures can be far less than the elastic result. This new method matches the practice better.

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STUDY ON DEFORMATION CHARACTERS OF RAILWAY INSULATED EMBANKMENT IN PERMAFROST REGIONS

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2007, 26 (08): -1670 doi:
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Due to special engineering geological characters of the permafrost，it is inevitable for the embankment above the permafrost to come into being deformation，even failure. To ensure the railway unblocked，it is necessary for the embankment in permafrost regions to meet not only the requirement of the thermal stability，but also the requirement of the structure stability. Based on the observation data of the insulated embankment in the Beiluhe test site along the Qinghai—Tibet Railway，the characters of the ground temperature and the deformation of the insulated embankment are analyzed；and the relationship between the ground temperature and the deformation is presented. The observation data indicate that the embankment deformation has close relationships with the ground temperature of the embankment，and is controlled by the ground temperature state and its change. The analytical results also show that the compressive deformation of the permafrost due to ground temperature rising partially results in the durative deformation of the insulated embankment which cannot be ignored. The thaw settlement results in the biggest embankment deformation. According to the analytical results，taking the fact that the permafrost temperature strongly controls the physico-mechanical properties of permafrost into consideration，an embankment deformation model，which considers the factors such as the compressive deformation，the thaw settlement etc.，is established. The railway embankment deformations in the coming 50 years are simulated. The computational results indicate that the less embankment height and lower mean annual air temperature result in the smaller embankment deformation. On the contrary，the larger railway embankment deformation will be brought if the railway embankment is high and the area has high average annual air temperature.

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NUMERICAL ANALYSIS METHOD FOR TEMPERATURE FIELD OF FREEZING-THAWING SHALE BASED ON DIGITAL IMAGE PROCESSING

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2007, 26 (08): -1678 doi:
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Combining technique of digital image processing and finite element software ANSYS，the CT image of freezing-thawing shale is processed；and the meso-structure image of shale is obtained. The law of temperature field of freezing-thawing shale is analyzed in negative temperature condition. Study results show that the digital image processing method can be used as a measurement tool to construct a digital representation for actual spatial distribution of different materials in shale. It not only can accurately describe the spatial distribution of shale damage but also can get the maximum use out of hidden information in CT image of shale. The meso-structure image is incorporated into finite element software ANSYS to achieve the goal of simulating temperature field law of freezing-thawing shale with consideration of the actual spatial distribution of meso-medium and initial shale damage. The following conclusion is drawn by analysis. The meso-structure determines the distribution of temperature field of freezing-thawing shale and also has an important influence on freezing-thawing damage process. The proposed approach can grope for the hazard reasons in view of meso-scale and provide a new way to research the inherent mechanisms of frost heave，thaw settlement and the consolidation of frozen ground.

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STUDY ON APPLICATION OF DIGITAL CLOSE RANGE PHOTOGRAMMETRY TO MODEL TEST OF TUNNEL IN JOINTED ROCK MASSES

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2007, 26 (08): -1684 doi:
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The application of the close range photogrammetric technique to the model test of tunnel in intermittent jointed rock masses is presented. The developed software package Photoinfor is used to capture the deformation patterns and to analyze the deformation evolution quantitatively during loading on the model edges. Meanwhile， a simple but effective approach，image borehole method，which is based on the digital image correlation method，is proposed to recognize and measure the rock broken zone around tunnel accurately. In this approach，some groups of image borehole，which are some straight-line-like pixel points with one pixel interval on test image，arrange symmetrically around the tunnel center along the radial surrounding rocks and are analyzed by the software PhotoInfor. The broken rock zone can be determined accurately according to the position of pixel point with rapid displacement change along the image borehole. By the approach，a phenomenon of rock masses re-breaking in broken rock zone is also found. This may be helpful to study the mechanical behavior of rock masses inside the broken zone. The result shows that the photogrammetric technique is a powerful tool for deformation measurement in the geotechnical experiment not only for the granular materials，which is more widely studied at present，but also for the rock similarity simulation test.

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TEST AND NUMERICAL ANALYSIS OF MODEL ROCK-SOCKETED PILE

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2007, 26 (08): -1691 doi:
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Rock-socketed piles can hardly be loaded to failure in field tests due to their high ultimate bearing capacity. In order to investigate the pile resistance behavior along the concrete-rock interface，two rock-socketed pile models were tested in laboratory. One model was loaded to failure at the maximum applied load. It was observed that the slippage occurred along the concrete-rock interface，while the pile body and the rock mass remained intact. The mobilized pile resistance along the concrete-rock interface within the rock-socketed section was evaluated from the recorded axial strains. The results indicated that the shaft resistance was not evenly mobilized within the socket. It is clear that the mobilized pile resistance in the upper zone is much greater than that in the lower zone. In addition，a serious of numerical simulations of tests were performed by using a finite element program. The interfacial elements were adopted in the program to model the concrete-rock interface behavior. The numerical analyses indicated that notable normal stress could be produced along the concrete-rock interface due to the lateral deformation in the rock mass. The mobilization of the pile resistance along the interface was greatly influenced by the normal stress. Therefore，the mobilized pile resistance in the upper zone is much greater than that in the lower zone. The investigation suggests that the pile resistance behavior along the concrete-rock interface can dominate the working performance of the rock-socketed piles constructed in hard rocks. Furthermore，the pile resistance along the concrete-rock interface can be greatly influenced by the deformation characteristics of rock mass.

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STRESS STATE VARIATION AND PRINCIPAL STRESS AXES ROTATION OF GROUND INDUCED BY MOVING LOADS

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2007, 26 (08): -1698 doi:
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Based on Euler-Bernoulli beam in elastic half space and its dynamic solution under moving loads，the solution of reaction force between ground surface and beam is presented. Exerting the reaction force on the ground surface，the corresponding steady-state stresses in ground are obtained by integrating the basic solution of a moving point load on elastic half-space surface. The results are valid only for load with speed lower than Rayleigh wave velocity in ground. Taking one wheel moving load as an example，the stress state variation，principal stress axes rotation and the influence of load speed are analyzed. The time-history curve of stress，stress path and curves of the principal stress axes rotation of soil element under and beside the load moving line are presented. It is found that the principal stress axes rotate 180°for soil element under the load moving line during the load running； and stress state changes from the pure shear to triaxial shear and back to pure shear. When the load speed is relatively high，the speed affects the variation of stress state greatly；and the dynamic response induced by moving load is very great. So it is not reasonable to analyze the stresses by the static method. For soil element beside the load moving line，stress state variation and principal stress axes rotation are very complex，but are similar with those of soil element under the load moving line in x-z and x-y planes.

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DYNAMIC RESPONSES OF TRACK SYSTEM AND SATURATED SOIL IN HALF SPACE SUBJECTED TO A MOVING TRAIN LOAD

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2007, 26 (08): -1705 doi:
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The dynamic responses of track system and saturated soil in half space subjected to a moving train load are investigated analytically. The system is divided into two parts，the track and the ground. The track system consists of three parts：rail，sleepers and ballast. The rail is modeled by introducing the Green function for an infinitely long Euler beam subjected to the action of the moving train load and the reaction of sleepers. The sleepers are represented by the continuous masses. The effect of the ballast is considered by introducing the Cosserat model. Neglecting the gravity of the soil medium，the Biot theory of a fully saturated poroelastic half-space is employed. By making use of the double Fourier transform，the governing equations of motion are solved in the frequency-wave-number domain. The governing equations of the soil medium and the track system are coupled by the boundary condition on the surface of the ground. The time domain responses are evaluated by the inverse Fourier transform computation for the cases that train velocity is lower or higher than soil Rayleigh-wave velocity .Computed results show that the dynamic responses of soil medium and rail are considerably affected by the fluid phase as well as train velocity. At low train velocity，whether the soil is considered as poroelastic medium or elastic medium only influences the amplitude of the soil and rail displacement. However，the responses for poroelastic medium are quite different from those for elastic medium when the train velocity exceeds Rayleigh-wave velocity of the soil medium.

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STUDY ON STRAIN SOFTENING MODEL OF SATURATED SOFT CLAY UNDER CYCLIC LOADING

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2007, 26 (08): -1713 doi:
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Degradations of stiffness and strength will occur in soft clay under cyclic loading because of the generation of pore pressure. Unfortunately，previous work rarely incorporates the effect of anisotropic consolidation on cyclic degradation behavior of soft clay. In addition，most of the previous tests were performed with a lower cyclic frequency when considering strain softening. The strain degradation characteristics of saturated soft clay subjected to undrained cyclic triaxial loading is investigated at different cyclic numbers，cyclic stress ratios，consolidation ratios，overconsolidation ratios and frequencies of cyclic loading. It is observed that the degradation index reduces with the progressive cyclic numbers and the increase of cyclic stress ratio. There is a critical cyclic stress ratio in clay subjected to cyclic loading. When the cyclic stress ratio is much higher or lower than the critical cyclic stress ratio，the relationship between degradation index and lgN is linear. However，when the cyclic stress ratio is around critical cyclic stress ratio，a nonlinear relationship is observed. On the other hand，higher frequency and overconsolidation ratio decrease the degradation index of soft clay. For anisotropic consolidated clay，the degradation index reduces with the increase of consolidation ratio at a lower cyclic stress ratio. At a higher cyclic stress ratio，the degradation index of anisotropic consolidated clay will be greater than that of normally consolidated soils with increasing cyclic numbers. A nonlinear relationship is obtained if the degradation index is plotted against the cyclic numbers on a semi-log scale. This relationship has been synthesized in the form of an empirical equation. This empirical equation is further used to describe the dynamic stress-strain relationship of saturated soft clay according to modified Iwan¢s model.

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RESEARCH ON APPLICATION OF ELECTRICAL RESISTIVITY MODEL THEORY TO CREEP BEHAVIORS OF MARINE SOFT SOIL

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2007, 26 (08): -1720 doi:
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Based on the test measurement，the electrical resistivity model of Lianyungang marine soft soil is established；and this model is applied to illustrate the change rule of microstructure of Lianyungang marine soft soil during creep. Furthermore，the soft soil creep value is estimated by the means of electrical resistivity indices. And then，the correlation between the microstructure and the creep is demonstrated；and the parameter M，integrative electrical resistivity structure factor，can well evaluate the creep value of marine soft soil. Applying the electrical resistivity model to study quantitatively the soft soil microstructure，this method will radically overcome some deficiencies of conventional microstructure method and greatly improve the operability and consistency of obtaining soil microstructure indices. Accordingly，a new method is presented to illuminate the change rule of microstructure of marine soft soil during creep and to estimate the creep of soft soil.

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博士论文摘要

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2007, 26 (08): -1728 doi:
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[PDF 103 KB] (1105)

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2007, 26 (08): -1728 doi:
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[PDF 150 KB] (973)

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《岩石力学与工程学报》第5，6期EI收录文章