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2005, 24 (13): 0-0 doi:

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2005-13期目录

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PROBLEMS OF DEFORMATION AND BEARING CAPACITY OF ROCK MASS AROUND DEEP BURIED TUNNELS

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2005, 24 (13): 2203-2203 doi:

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The behavior of rock block on a macro-scale is described by the classical mechanics of continuum，while the discontinuous displacement field between rock blocks is represented by a combination of smooth functions，which characterizes the deformational behavior of rock block interfaces. Hence，the way is mathematically described in which the energy is stored，dissipated and transferred between rock block interfaces. In the context of the proposed procedure，taking the determination of rock pressures on a circular tunnel for example，the proportion of pressures around the tunnel resisted by each zone is calculated based on a simplified stress-slip displacement relation；the direct relationships among the rock pressures and the buried depth，dimensions and shape of the tunnel，the physico-mechanical characteristics of rock mass，and the flexibility of supports and etc.，are illustrated.

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MACROSCOPIC MODEL OF HYSTERESIS AND MEMORY FOR THE DESCRIPTION OF ROCK NONLINEAR ELASTIC

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2005, 24 (13): 2212-2212 doi:

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We introduce the macroscopic model of nonlinear elastic materials，Preisach-Mayergoyz model(PM model). PM model is founded by the response of the pair of stresses( )of many hysteretic mesoscopical units(HMU)versus loading and unloading；and it¢s nonreversible through the original path. Porous saturated rocks have characters of hysteresis and discrete memory to describe. Based upon the hypothesis that the macro nonlinear elastic properties of porous rock are caused by an enormous variety of mesoscopical structural features such as cracks，joints and contacts；we have simulated hysteresis and discrete memory in rock by the PM model. The curves of stress-axial strain，stress-radial strain in the rock are determined by the space density and elastic properties of HMU in PM model. The elastic moduli have close relation with distribution of PM space density and a pair of equilibrium length of HMU. The treatment in PM model emphasizes the importance of stress history in the determination of the elastic state of a rock. The PM space density reflects the constitutive relationship response of a rock under cyclic loading in some degree. We argue that hysteresis is the cause of discrete memory in rock through the simulation of a rock¢s discrete memory. We can also use the equation of the stress-strain state to simulate the discrete memory of a rock observing in the experiment.

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STUDY ON DEFORMATION FAILURE MECHANISM OF GAOJULI¢S JIANGJUNFEN OF NATIONAL KEY CULTURAL RELIC PRESERVATION ENGINEERING

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2005, 24 (13): 2220-2220 doi:

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Based on the field investigation and the engineering geological exploration，the deformation failure characteristics of Jiangjunfen was analyzed. The changes of the stress field and the rules of the deformation failure of Jiangjunfen under three cases，the gravity field and the local soft foundation and the ground water seepage field，were researched respectively using FLAC technique. The simulation results show that the deformation failure mechanism of Jiangjunfen is a gradual developing process. Firstly，the whole structure of Jiangjunfen subsided into the local soft foundation，then leading to the decline of the northern part of the structure，accompanying with the tensile fracture among stones and the heaving of the groundsill，and at last resulting in the stones sliding and the large scale structure deformation failure of Jiangjunfen. It is helpful to evaluate the stability of Jiangjunfen and to adopt preventing measures to control the evolutional deformation of Jiangjunfen with the research conclusion.

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ON DEFINITIONS OF SAFETY FACTOR OF SLOPE STABILITY ANALYSIS WITH FINITE ELEMENT METHOD

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2005, 24 (13): 2225-2225 doi:

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There exist three definitions of safety factor in slope stability analyses by limit equilibrium methods (LEM). Definition 1 defines the safety factor as the ratio of the shear strength of soil to the shear stress required for equilibrium. Definition 2 defines the margin of safety factor as the factor of the strength reduction，by which the shear strength of the soil would have to be divided to bring the slope into a state of critical equilibrium. Definition 3 defines the safety factor as the ratio of the resistant shear force to the driving shear force along a certain slip surface. This study discusses the relation between Definition 1 and 3. A unified algorithm is given，which is used to locate the critical slip lines corresponding to Definition 3 and Definition 2 respectively. It is also proved while the finite element method is used to analyze slope stability，both the safety factor and the potential slip surface based on Definition 3 are different from those on Definition 2. Some irrational results might be obtained if Definition 3 is used in finite element slope stability analysis.

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ELASTOPLASTIC CONTACT FEM ANALYSIS OF BEDDING LANDSLIDE STABILITY

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2005, 24 (13): 2231-2231 doi:

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Contact FEM strength reduction method is an inverse process in limiting equilibrium analysis of slope stability. Based on the results of reported documents and engineering practice，correlations between nonlinear FEM strength reduction analysis and limiting equilibrium analysis of slope stability are established. The result lays more sufficient foundation for making full use of the advantages of both methods above in the analysis of slope stability；and it guarantees the reliability of calculation of the safety factor and analysis of slope stability. The principles of determining strength parameters of slide mass and glide，density of slide mass，meshing accurately finite element，and determining convergence criteria are established. According to analysis of engineering concrete example，it is testified feasibly in the analysis of slope stability and the calculation of the safety factor. Therefore，it may act as a reference to the analysis and calculation of the similar landslide. The stability of decomposed-rock bedding slope with high nonlinear problem is analyzed by FEM strength reduction of non-separation contact elastoplastic model，which may more clearly reflect actual state of slope deformation and failure.

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BACK ANALYSIS OF CRITICAL FAILURE SURFACE OF SLOPE BASED ON BIONICS ALGORITHM(1)—LOCATION OF CRITICAL FAILURE SURFACE

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2005, 24 (13): 2237-2237 doi:

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Location of critical failure surface and identification of its parameters are two very important problems in slope stability analysis. At first，location of critical failure surface is studied. Here，the coordinates of some reference points are taken as searching objectives，so the problem of location of critical failure surface is transformed to a typical complicated optimization problem that can not be solved by traditional optimization methods. To solve this problem，the new global optimization method that is called bionics algorithm-immunized evolutionary programming is introduced. So，taking the coordinate of reference points as optimization parameters and safety factor as optimization objective，a new method to search critical failure surface is proposed. At last，through a typical numerical example and an engineering example，this new method is verified. The results show that this new method can solve the problem of location of critical failure surface very well and can be applied to engineering practice. But only to locate the critical failure surface with supposed parameters can not get the suitable safety factor of slope，the better way is to search the critical failure surface and its parameters at the same time. This problem can be solved in the second part of this paper.

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STUDY ON SELF-BALANCE DESIGN THEORY OF CULVERT GRID ADVANCED IN PIPE-ROOF IN SATURATED SOFT SOIL LAYERS

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2005, 24 (13): 2242-2242 doi:

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At present，during the construction of advancing culvert box at home and abroad，the soil in front of box should be reinforced to retain stability. The tunnel of Shanghai Middle Ring Line located in the intersection of Hongxu Road and Beihong Road will be the first case to adopt pipe roof culvert box advancing scheme without reinforcing the saturated soft soil layer to decrease project cost. In order to sustain the stability of surface and control the ground settlement during the construction，the reasonable design of girding will be crucial. Based on the principle of mechanics and some hypothesis，this paper takes advantage of the balance between friction and earth pressure in grid，and presents a kind of self-balance design theory. A differential equation is set up and the distribution and attenuation rules of soil pressure，normal stress，shear stress and etc. are obtained. These rules of stress distribution and attenuation conform to a series of exponential equations. In addition，the critical length of grid and the relations among length，width and height have been obtained from the equations. Also，the main factors affecting the critical length of grid are analyzed from these equations and are obtained as follows：the soil pressure in front of grid；frictional property between soil and grid wall；soil friction angle and cohesion. Analysis indicates that the critical length is increased as the soil pressure increasing and decreased as the friction factor increasing. These equations and results can be regarded as academic foundation for grid design for soft soil layers.

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UNLOADING-INDUCED DEFORMATION AND STRENGTH PROPERTIES OF LOESS DURING CONSTRUCTION

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2005, 24 (13): 2248-2248 doi:

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During excavating tunnels and subway tunnel with shield，different unloading effects in construction occur to disturb surrounding earth and adjacent buildings. The change of stress state and stress path，as a principal factor，plays an important role in disturbance caused by various construction activities. For example，the states of stress and consolidation at sides and bottom of pit change during excavation. In the process of shielding，earth surrounding the gaps of shield ends takes various unloading effects to alter the stress states. There exist compressive disturbances in the earth right in the front of tunneling. The gaps between the end of shield and lining give rise to moving and loosened earth to form unloading disturbance areas. In current theories of design and calculations，loading models are usually applied without really considering the unloading effect in excavation. Besides，the factors of various construction methods，indefiniteness of underground construction and complexity of surrounding environment have all contributed to make underground construction as risky projects，which have rendered several disastrous accidents in recent years that jeopardize life and property，adjacent buildings，underground pipelines and interrupt intercommunication systems. Based on the analysis of unloading effects in different types of construction and various construction conditions，this paper proposes some laboratory test schemes for loess with methods of unconventional triaxial shear to conduct a series of study on the behaviour of stress-strain relationship，characteristics of strength，deformation and failure on dissimilar unloading stress paths. The test results show that behaviors of strength，deformation and failure under unloading paths are much different from those under loading paths. The shear strength at extension failure is less than that at compression failure. The maximal axial strain at extension failure takes only 1/3-1/2 of compression failure.

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PROTECTION PILLAR STABILITY NUMERICAL SIMULATION IN SHALLOW SEAM COVERED WITH ROCK SOIL AND SAND

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2005, 24 (13): 2255-2255 doi:

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The key to realize water retention during mining is to determine the reasonable working face¢s advancing distance and the reasonable coal pillar size in shallow coal seam；and the reasonable face¢s advancing distance resulting from simulation material experiment has been proved by the practice. The numerical simulation is designed on the basis of the water fluid crack¢s height in rock according to different face¢s advancing distances resulted from simulation material experiment. The stress and strain dimension distribution are calculated by the computer program “ALGOR”；and two kinds of faces have been simulated as following：(1) the rock thickness of less than 30 m and the soil layer of lower than 20 m；and (2) the rock thickness of more than 30 m and the soil layer of more than 20 m. According to the Von Mises stress distribution，the greatest tensile stress distribution on sinking belt and the greatest sinking distribution on sinking belt，the coal pillar and overturning rock¢s stability are judged and the reasonable face¢s advancing distance is drawn. It is significant to realize the water retention during mining in the geological condition of Shaanxi Province and the prevention of desertification in mining area.

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OPTIMUM DESIGN OF DIRECTION ANGLE OF PRESTRESSED ANCHOR CABLE IN SLOPE REINFORCEMENT

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2005, 24 (13): 2260-2260 doi:

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Taking the influence of the slope and sliding surfaces obliquities into account，a new method for determining the orientation angle of prestressed anchor cable is presented. The previous method，not considering the influence，is only a particular case of the presented method when the slope surface is parallel to the sliding surface. A range of choice for the orientation angle of prestressed anchor cable，satisfying working，constructional and structural requirements，is given. The reinforcing effect is compared between these two methods；theoretical analysis and calculation examples all confirm the advantages of the presented method over the previous one. Calculation results show that the reinforcing effect ratio of presented method to previous method is increscent with increase of the difference(absolute value) between the slope and sliding surfaces inclinations and with decrease of friction angle of sliding surface. And the increscent speed is more rapidly when the inclination angle of sliding surface is less than the inclination angle of slope surface. The presented method is especially suitable to the case when large number of prestressed anchor cables in slope reinforcement are used.

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NUMERICAL SIMULATION IN MINING PRESSURE CONTROL OF THICK AND STRONG STRATUM CAVING BY WATER-INFUSION SOFTENING METHOD

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2005, 24 (13): 2266-2266 doi:

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The caving of thick and strong roof stratum，key stratum，causes tremendous rock pressure in mine. In order to control the rock pressure effectively，the thick and strong roof strata，of which the softening factor is relatively small，can be treated previously by boring and high pressure water infusion，water infusion softening method. With the help of RFPA2D software，the strata behaviors of different parameters，softening factors and softening thickness of the stratum in a mine，are simulated numerically. In the numerical simulation，different values of mechanical parameters of the softened parts of the roof stratum，Young¢s modulus，compressive strength，tensile strength and etc.，are taken for corresponding values of softening factor. Relations between the parameters and softening effect are studied. The first caving distance and rock pressure of overlying strata decrease as the softening factor decreases and the softening thickness increases. For practical mining engineering，the two parameters have to obtain some certain values to realize good roof control. There are some mining faces，where though the rock can be softened by water infusion，geological condition of a mine and mining technology makes the using only of water-infusion softening method not very effective，other methods，or combined with water-infusion softening method，should be adopted.

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THEORETICAL SOLUTION FOR SHEAR STRESSES ON INTERFACE OF FULLY GROUTED BOLT IN TUNNELS

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2005, 24 (13): 2272-2272 doi:

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Based on the displacement formula of the tunnel wall，the shear stress on the interface of the fully grouted bolt is educed．Compared with the in-situ measurements，the different shear stress distributions are described for the distortion region，transition region，and stabilization region. The model of bolt shear stress in loose region is proposed；and the position of neutral point is obtained. Based on Mindlin¢s solution of displacement，the shear stress on the interface of the bolt behind neutral point is also derived considering the axial force of neutral point as concentrated force.

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A NOVEL DERIVATIVE SPLIT GROUTING PHENOMENON

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2005, 24 (13): 2277-2277 doi:

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During the process of grouting the marble dam foundation of the existing earth dam of Wanghuating reservoir，there were some unusual phenomena such as splitting dam body，splitting slots on dam crest，emitting grout from dam crest or dam gradient. That is a novel splitting grouting phenomenon. Considering that the grouting material was cement slurry，it influenced the character of existing earth dam after being congealed；people were worried about the new hidden dangers due to the grouting. This paper compared and analyzed the new derivative split grouting phenomenon with the Zhang¢s grouting method based on introducing the traditional derivative split grouting method. It is suggested to study the novel splitting grouting phenomenon such as the conjunction degree between calculus formed by the cement slurry which split the dam body and earth，the shape of the calculus，the transfiguration of calculus and dam body and earth，influence in the structural safety and seepage safety caused by calculus，and grouting theory and etc.. It will not only be benefit to the practical grouting but also promote development of grouting theory.

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SYNTHETICAL FUZZY CLUSTERING ANALYSIS FOR JOINTS OCCURRENCE OF ROCK MASS

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2005, 24 (13): 2283-2283 doi:

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The analysis of joints occurrence in rock mass is an important basic work for mechanical and hydrodynamical behaviors analysis of rock mass. Traditional analysis of plots methods is inadequate to this work；therefore a fuzzy clustering analysis is developed. Both the advantages and disadvantages of fuzzy clustering method and ISODATA fuzzy clustering method are analyzed；then the two fuzzy clustering methods are combinated into a synthetical fuzzy clustering method；and a procedure of the synthetical fuzzy clustering method is proposed. A case study shows that the results of the synthetical fuzzy clustering method are reasonable and reliable.

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STUDY ON SLOPE STABILITY BY DUAL INDEX SYSTEM BASED ON NORMAL DISTRIBUTION

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2005, 24 (13): 2288-2288 doi:

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The traditional method of slope stability analysis is safety factor，and its applications have long time，broad prospects and abundant experience. However，the weakness of safety factor is that it can not consider uncertainties of parameters and models，for which，especially uncertainty of parameters，has a great influence on slope stability. Reliability theory can effectively solve uncertain and correlative problems in slope system. However，reliability theory is complicated and short of abundant experience. Therefore，it is necessary to build dual index system of slope stability coupling safety factor and reliability. Most likely safety factor (mean safety factor) was calculated with average value of parameters，and reliability of slope was calculated with variability of safety factor. Supposing that safety factors obey normal distribution in different maximum possible safety factors and variation coefficients，a series of most likely safety factors and variation coefficients of safety factor were taken，and failure probabilities of slope Pf were calculated. In this way，a series of most likely safety factors and failure probabilities were obtained. Multiplied most likely safety factor by corresponding reliability，reduced most likely safety factor，reliability safety factor of slope was obtained. From limit state of reduced safety factor，critical failure probabilities and variation coefficients corressponding different maximum possible safety factors were calculated. According to different maximum possible safety factors and their failure probabilities，divisional chart of slope stability was drawn. Choosing representative safety factor and its reliability，dual index system of slope stability coupling safety factor and reliability was built，by which slope stability could be measured. As a research example，stability of Yancun landslide was assessed with dual index system of slope stability；and research result shows that dual index system of slope stability is feasible method. Estimation of variance with moment estimation was expounded in little sample size.

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EIGEN THEORY OF GENERALIZED PLASTIC MECHANICS FOR ANISOTROPIC SOLIDS

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2005, 24 (13): 2293-2293 doi:

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Based on the eigen theory of solid mechanics under the standard spaces，the generalized plastic mechanics with multiple-yield-surface model is rebuilt；in which some fundamental laws of anisotropic plastic mechanics such as the anisotropic yield surface，anisotropic hardening condition，anisotropic plastic flow rule and anisotropic loading and unloading criterion，are studied and put into the form of formula. According to them，the wave equations and static equations for anisotropic elastoplastic body are obtained. It is proved that there exist the potential functions of stress increment for anisotropic elastoplastic statics. Finally，the propagation properties of anisotropic elastoplastic wave are discussed and a concrete example of anisotropic elastoplastic mechanics is presented.

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NUMERICAL SIMULATION ON CUTTING MODE OF SHAFT EXCAVATION BY ONE-STEP DEEP-HOLE BLASTING IN HARD ROCK

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2005, 24 (13): 2298-2298 doi:

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By using the LS-DYNA 3D nonlinear dynamic finite element software，the elasticity calculation model was established to analyze the generation and transmission of stress under explosive charge in 4 typical cutting patterns，those used in shaft excavation by one-step blasting were optimized and compared by numerical simulation to select the optimizing cutting patterns. The 4 typical cutting patterns are：9-hole cut，single-spiral-hole cut，double- spiral-hole cut，and 2-empty-hole-diamond cut. LS-DYNA 3D nonlinear dynamic finite element software was applied to simulate the shaft excavation by one-step blasting to achieve the generation and transmission mechanism of stress wave，which would be helpful for selecting the best cutting pattern. The simulation results showed that the single-spiral-hole cut was the optimum cutting pattern according to the related parameters such as the maximum generating time of stress，the generating time of stress around the empty holes，the action time of available stress，and the maximum velocity of node and the penetrating time of stress. The research results of numerical simulation have been proved by field productive application. The bottleneck problems referring to the blasting parameters in shaft excavation by one-step blasting have been solved. This research presented a scientific and reasonable theory for the underground engineering and would have the wide application prospect in the future.

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RESEARCH ON COUPLING LAWS BETWEEN EME AND STRESS FIELDS DURING DEFORMATION AND FRACTURE OF MINE TUNNEL EXCAVATION BASED ON FLAC2D

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2005, 24 (13): 2304-2304 doi:

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The distribution laws of stress fields in the course of mine tunnel excavation are simulated by means of FLAC2D software. According to the stress values and the coupling laws between electromagnetic emission(EME) and stress fields during the deformation and fracture of coal or rock，the changing laws of EME during mine tunnel excavation are also researched. The researching results show that the electromagnetic emission signals have the biggest value in the middle of tunnel. The monitored EME values are very varied under different loading stresses. The higher the loading stress is，the stronger the EME signal produced is. The EME values received in the detecting place will decrease in line with power rate relation with the increasing of EME frequency. And it is feasible to regard the stress concentrating area as EME resources. The EME in the same monitoring place increases firstly，and then increases slightly with the increase of time. The changing of EME strength reflects the changing of inner stress after excavation. The experimental results of EME have the same changing tendency as the simulated results，which also testify the feasibility of the coupling method between EME and stress. Thus it is offered a kind of new research approach to electromagnetic emission monitoring technology for the purpose of the application of monitoring EME in the prediction of catastrophe dynamic phenomena such as coal or rock outbursts.

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SETTLEMENT CALCULATION OF PILE FOUNDATIONS WITH ELEVATED CAPS BY LOAD TRANSFER METHOD

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2005, 24 (13): 2310-2310 doi:

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Settlement calculation is one of the key problems in the design of pile foundations with elevated caps. To analyze the settlement characteristics of pile groups with elevated caps，the displacement fields in the surrounding soil of each pile in the group caused by shaft resistance are firstly obtained by the Cooke¢s method. Then，with the new displacement fields obtained by considering the reduction effect caused by the existence of piles and superimposing the displacement fields in the surrounding soil of each pile in the group，the equivalent stiffness coefficients of unit thickness soil around each pile are developed，taking into account the interaction among the piles. The Boussinesq solution is modified to include the effect of different embedded depths and then used to derive the equivalent stiffness coefficients of the soil under the pile toe. Based on these two kinds of coefficients and the load transfer method，a new method to predict the settlement of pile groups with elevated caps is advised with relevant calculation formula provided as well. Finally，to verify the presented method，the results of a model test of pile foundation are analyzed and compared with the predicted settlements；and a good agreement between them is obtained.

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PRELIMINARY STUDY OF STABILITY OF LEVEE ON SOFT GROUND

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2005, 24 (13): 2315-2315 doi:

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Muddy clay from the soft ground of Huaihe River¢s levees for a flood channel to sea was retrieved and remolded to investigate the mechanism of stability of levees on soft ground after the end of construction and during rapid drawdown of water level，respectively，by centrifugal model tests. The safety factor against sliding was analyzed on the basis of slope surface displacement development while the location of slip was determined from the vector diagram of displacement on slope cross-section. It is observed from the overloading tests，by accelerating models over the predetermined g-level，that the sliding surface of the levee on soft foundation is deep seated one，which passes through the soft ground，after the completion of construction，whereas there is a failure surface，which passes through the toe of the slope but occurred earlier than the deep seated one，during rapid drawdown of water level. These test results show that the stability of the levee on soft ground is mainly governed by the bearing capacity of the soft soil layer and be influenced，to a certain degree，by action due to rapid drawdown of water level. Suggestion on more realistically modeling for stability behavior of levee on natural soft ground is also proposed on the basis of similitude consideration of inherent structure of in-situ clay.

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SOLUTION OF FREE SURFACE SEEPAGE PROBLEMS BY TREFFTZ DIRECT METHOD

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2005, 24 (13): 2322-2322 doi:

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Solution of seepage analysis with a free surface by Trefftz direct method is presented. Compared with traditional boundary element method and finite element method，Trefftz direct method avoids the difficulty of singular integral and the inconvenience of mesh modifications. Steady seepage and unsteady seepage with a free surface in a homogeneous earth dam were analyzed. Compared with a glycerin experimental result，the elevation of release point and its relative error are listed in a table. The numerical results show that the proposed method has its advantages. It takes less computation time and has satisfactory accuracy and convergence.

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STUDY ON FOAM TECHNOLOGY DURING SHIELD EXCAVATION IN SANDY COBBLE BED WITHOUT WATER

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2005, 24 (13): 2327-2327 doi:

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The main types of shield machine used recently in tunnel construction are earth pressure balance(EPB) shield and slurry shield. In order to keep muck discharged fluently and lighten machine burden，the soils in chamber of EPB shield should be plastic and fluid. This is fundamentally critical to ensure the shield to advance continuously and smoothly. Sandy cobble without water is a typically unstable stratum and its mechanical properties are unfavorable to force’s transitivity and spread. Sandy cobble is of unfavorable plasticity and fluidity，which is sure to bring serious wear of cutter wheel and screw. Moreover，earth pressure balance of face is not easily maintained and the face is easy to collapse. As a case of EPB shield construction，a sewage tunnel in Beijing is presented. In the beginning 200 m of the shield tunnel，field driving tests are carried out. Firstly mud is injected into the chamber to sustain the plasticity and fluidity，but perfect effects are not acquired. Then foam technology is studied experimentally and used in field shield construction，in which calculation method and dosage of the foam are recommended. Then test results between injection of mud individual and combined injection of mud and foam are compared；and oil pressure of the cutter wheel and the screwer of the later is about 1/3 of the former；surface settlements also decrease from 20 mm to 5 mm. Finally，the mechanism of foam effects is analyzed and its effects can be summed up to two aspects as following：(1) forming a admixture level in the tunnel face composed of sandy cobbles，mud and foam；(2) forming a thin membrane around every granules. Study and practice prove that the mud and foam are not only beneficial to earth pressure balance，but also can lighten mechanical load and abrasion，which are remarkably significant to smooth cutting，soil discharge and high-speed advance of the EPB shield.

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STUDY ON INFLUENCE OF SAND-AND-GRAVEL LAYER THICKNESS UP BLOCK-STONE RAILWAY EMBANKMENT ON COOLING EFFECT OF FROZEN-SOIL FOUNDATION

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2005, 24 (13): 2333-2333 doi:

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In block-stone embankment construction of Qinghai—Tibet railway，different thicknesses of upper sand-and-gravel layer and same thickness of block-stone layer were used in different railway segment due to the uneven landform. By numerical stimulation，the temperature distribution were obtained in common embankment and block-stone embankment with upper sand-and-gravel layer in different thicknesses. The comparative analyses show that block-stone embankment has well active cooling effect on the railway foundation by raising the permafrost table and decreasing the permafrost temperature，and the variation of upper sand-and-gravel layer thickness has also great influence on the active cooling effect. The thicker the upper sand-and-gravel layer is，the smaller the temperature variation magnitude on the top of block-stone layer conducted from the embankment surface is，which will slow down the convection speed of the air in block stone and weaken the cooling ability of block stone. Although the permafrost table under the center of the embankment lifts up with thicker upper sand-and-gravel layer，the cost is the frozen intensity decreasing of the permafrost and the dissipation of cold generated by the block stone near the embankment foot. On the conditions given by the model，the cooling ability of block stone is stronger than that of heat disturbance caused by embankment construction when the thickness of upper sand-and-gravel layer is less than 6 m or larger than 9.5 m. The cooling of block stone near the embankment foot and the cold supplying of around permafrost can not counterweigh the heat effect of embankment anymore and the permafrost table under the center of the embankment will go down gradually. In sum，the increase in the thickness of upper sand-and-gravel layer will weaken the active cooling ability of block stone and lower the permafrost table beneath the railway embankment，and while the thickness exceeds a certain number the middle zone of block stone will almost loss the cooling capability and thus lead to an increase of permafrost temperature，which is disadvantageous to the stability of railway embankment and the protection of cold ground. Considering the warm tendency of global climate and the heavy load of high embankment，we suggest the discussion of thick sand-and-gravel layer up the block-stone embankment and seeking an optimal thickness of upper sand-and-gravel layer and block stone layer in construction.

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RESEARCH ON THE STRESS-STRAIN OF SHUIBUYA CONCRETE FACE ROCKFILL DAM BASED ON THE CONCRETE CRUSHING-TYPE SIDE WALL TECHNOLOGY

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2005, 24 (13): 2342-2342 doi:

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The concrete crushing-type side wall technology is a new method for constructing the upstream side-slope of concrete face rockfill dam(CFRD). Compared with the traditional method，this technology is obviously more advanced such as enhancing the project quality，quickening the pace，increasing the safety of river diversion and etc.. Further more，the technology has simplified the construction procedure and cut down the construction cost. However，It¢s still uncertain about the effect of the concrete crushing-type side wall on CFRD，particularly on its stress-strain. This paper，applying the advanced grid discreteness technique and the method to solve large scales of equations，researches the stress-strain of Shuibuya CFRD based on the concrete crushing-type side wall technology. Through calculating，it indicates that the concrete crushing-type side wall can not only replace the procedure of bedding material extra-filling，scaling，dressing，roller compacting and slope face protection，so as to quicken the schedule and enhance and guarantee the construction，but also improve the stress situation of the face and its deformation.

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RESEARCH ON FRACTURING AROUND CEMENTED SLOT IN ROCK SPECIMEN

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2005, 24 (13): 2350-2350 doi:

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The finite element simulation of sub-crack development around a fracture cemented with grout in Fangshan marble plate specimen under uniaxial compression is carried out. The initiation，coalescence and recovery of sub-crack around as well as inside the cemented fracture are photographed and analyzed under real-time scanning electron microscope observation. Finite element computation of the crack process using NOLM program with a strain-softening constitutive model of low tensile strength is performed. The computation result represents the experimental observation fairly well. The real fracture or fault system in earth，no matter in small or large scale，has filling materials such as fault gouge or fault clay which has lower strength. Compared with the field observation，the cemented one should be a better simulation of the actual geological situation. Therefore the results give a more comprehensive understanding and simulating of fracturing process in geologic structure.

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ANALYSIS OF CONSTRUCTION EFFECTS OF CHANGLIANGSHAN TUNNEL DURING EXCAVATION AND SUPPORTING IN HORIZONTAL SOFT SURROUNDING ROCK MASS

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2005, 24 (13): 2357-2357 doi:

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In light of the construction difficulty during building a long tunnel in soft rock mass，the 3D numerical simulation is used to analyze the construction schedule of the Changliangshan tunnel. According to the numerical simulation results，the characteristics of rock stress distribution and rock deformation becomes explicit in the case of short excavation footage. Consequently，it is reasonable to take above-mentioned construction scheme to excavate Changliangshan tunnel.

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DYNAMIC BEHAVIORS OF PILE FOUNDATION OF HIGH-SPEED RAILWAY BRIDGE UNDER LONG-TERM CYCLIC LOADING IN SOFT SOIL

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2005, 24 (13): 2362-2362 doi:

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Parameters of dynamic test are obtained from the analysis of pile foundation of small-span bridge for high-speed railway；and these parameters have been used in dynamic tests on bored piles in soft soil. Research is accomplished on amplitude of dynamic displacement，settlement at top of pile，axial force distribution of pile shaft，dynamic side resistance，axial stiffness of single pile and bearing capacity of piles under long-term cyclic loading. With the increasing of cyclic loading times，the results indicate that：(1) shaft force distribution of bored pile is different from that of original cases under long-term cyclic loading；and this difference mainly concentrates on top of 1/3 pile length；(2) enhancing effect of dynamic side resistance and degradation effect of dynamic side resistance are obtained in sand soil；(3) ultimate bearing capacity of single pile changes very small under the testing conditions；and (4) cyclic loading can induce decreasing of axial stiffness of single pile.

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IMPROVEMENT OF SIMPLIFIED PROCEDURE FOR LIQUEFACTION POTENTIAL EVALUATION OF SANDS BY SHEAR WAVE VELOCITY

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2005, 24 (13): 2369-2369 doi:

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Evaluation of soil liquefaction potential is an important aspect of geotechnical engineering practice；and several types of evaluating procedures have evolved over the past 30 years. In the current study，the simplified procedure using shear wave velocity measurements for liquefaction potential assessment was improved from the experimental results of undrained cyclic triaxial tests on saturated sands with shear wave velocity measured by bender elements. This improved simplified procedure establishes its correctness and feasibility essentially upon the warranted correlation between liquefaction resistance and elastic shear modulus of sandy soils，which is almost irrespective of soil types and confining pressures. Intensive evaluation of 26 earthquakes and more than 70 measurement sites shows that，the evaluation results using this improved simplified procedure are more consistent with the case history data than those from other evaluation methods within certain ranges of shear wave velocity. A case study is provided to illustrate application of the improved procedure. Additional studies are needed，especially for evaluating the liquefaction resistance of dense soil deposits shaken by stronger ground motions so as to further validate this improved simplified procedure.

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3D STABILITY ANALYSIS OF SLOPE BASED ON GIS AND PRINCIPLE OF MINIMUM POTENTIAL ENERGY

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2005, 24 (13): 2376-2376 doi:

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Making the best of data management and spatial analysis of GIS，this paper puts forward a method for 3D stability calculation of slope based on the principle of minimum potential energy；of which the adaptation to systematic analysis of sliding surface and mass，assumptions in traditional methods are avoided in this one. Geometric and mechanical parameters，which can be easily acquired from 3D geoscience model，are absolutely necessary for stability index calculation of slope with various shapes. Its rationality and fitness are proved by comparison of 2D and 3D calculation results.

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AXISYMMETRIC DYNAMIC RESPONSE ON LAYERED SATURATED VISCOELASTIC SOILS UNDER STEADY-STATE LOADS

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2005, 24 (13): 2380-2380 doi:

[PDF] 83 KB (786)

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Based on Biot¢s dynamic equation of porous material，the inertia force of both the soil and the fluid was considered，and the axisymmetric stable vibration problem of saturated viscoelastic soils with down lying rock stratum was studied. By the means of Hankel transform，the solutions were obtained in integral form. The numerical inversion of Hankel transform was used to obtain some results showing that with the increase of the radius，the maximum vertical displacement decreased with fluctuation；it changed with the loading frequency；and the vertical displacement of elastic soils，which is varied with the radius，fluctuated sharper than that of the viscoelastic soils.

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IMPROVED METHOD OF FINITE ELEMENT ANALYSIS OF SLOPE STABILITY

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2005, 24 (13): 2386-2386 doi:

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Two kinds of stress-strain relationship are used for different areas to evaluate the stability of slope，where the boundary effect can be eliminated efficiently and the natural state of slope can be simulated. The slope safety factors acquired by strength reduction are compared with those by equilibrium method. Using the method，two examples including a steep slope and a slope with weak layer are shown，and then satisfied results are gotten.

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LANDSLIDE SUSCEPTIBILITY ZONING AND ITS PROBABILISTIC FORECAST

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2005, 24 (13): 2392-2392 doi:

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How to predict and forecast the landslide hazard effectively is always a key point for prevention from casualty and economic loss caused by landslides. Based on the coupling analysis of the geology and meteorology，it is possible to improve the precision of the landslide forecast. The occurrence of landslides is mainly controlled by the following three factors：topography，geology and rainfall. A new method of landslide probabilistic forecast is proposed considering the combination of geologic environment with weather conditions. The urban area of Chongqing，which is one of the cities with most serious landslides in China，is taken as the study example. Taking into account the geologic environmental factors such as slope gradient，slope shape，lithology combination，structures of rock mass and hydrologic geology，the landslide susceptibility zonation is conducted with the information model. The prediction criterion of landslides in each susceptibility subarea is established by two variable combinations：the maximum 24 hours rainfall and the antecedent effective precipitation of 15 days. Finally，the feasibility of the probabilistic forecast on landslides using weather prediction is discussed with an actual example.

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EXPERIMENTAL STUDY ON THE BEARING BEHAVIORS OF OVERLENGTH PILES UNDER HEAVY LOAD

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2005, 24 (13): 2397-2397 doi:

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Based on the static load test and stress measurement of overlength piles in deep soft soil foundation，the load transfer mechanism and bearing behavior of overlength piles under heavy load have been studied. Under heavy load，the overlength piles behave as end-bearing frictional piles，and their frictional resistance and end resistance are asynchronous and coupling. The slime affects the exertion of frictional resistance and end resistance，so it is necessary to clear up the slime of overlength piles¢ bottom under heavy load. At the same time，the frictional resistance will be degraded. The critical value of pile-soil relative displacement has a good correlation with settlement of pile top，and it is a function of pile diameter. When the settlement of overlength piles¢ top exceed (0.01-0.02)D in soft soil，the soil around pile will slide. Some suggestions for design and appliance of overlength piles have been discussed farther on the bearing mechanism；and guidances for theoretical research and technical design of overlength piles have been provided.