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2005, 24 (23): -0 doi:
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2005-23中文目录

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EXPERIMENTAL STUDY ON RELATION BETWEEN SEEPAGE AND STRESS OF SANDSTONE IN CT SCALE

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2005, 24 (23): -4203 doi:
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[PDF 434 KB] (1219)

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The relation between seepage and stress is an important problem in numerical analysis of coupled seepage and stress fields of rock mass. The triaxial compressive and seepage experiment of sandstone sample is conducted in the laboratory using triaxial loading apparatus，seepage pressure loading apparatus and medical SOMTOM PLUS CT scanner. By analyzing the experimental results，the porosity equation based on CT numbers is proposed in CT scale. Using the equation，the porosities，real flow rates in porous rock，specific discharge，permeability and the micro-pore diameters during the processes of stress and strain of a sandstone sample are calculated. Results show that the changes of the seepage parameters have closely relations to the processes of damaging and cracking in the sandstone sample. At the first stage of compression test，with the increase of axial compression，the porosity，real flow rate in porous rock，specific discharge，permeability and the micro-pore diameters in a sandstone sample decrease；and the porosity in the sample is closed under compression. After the micro-fracturing initiation in the sample，the porosity，the real flow rate in porous rock，the specific discharge，permeability and the micro-pore diameters increase with the increase of the axial compression. According to the relation between stress and strain of the sandstone sample in macro-scale，the deformation of the sandstone sample is in the elastic deformation stage before the macro-cracking occurrence. At the point of macro-failure，the porosity，the real flow rate in porous rock，the specific discharge，the permeability and the micro-pore diameters reach the maximum values. Meanwhile，it is discovered that the micro-fracture occurs at the elastic deformation stage of rock and the stress of micro-fracturing initiation occupies 45% of the peak strength of the sandstone sample under seepage pressure，but 55% without seepage pressure. This indicates that the strength of the sandstone sample reduces 10% due to seepage pressure.

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CUSP CATASTROPHE MODEL OF RELATIONS AMONG
PERMEABILITY，STRESS AND STRAIN OF ROCKS

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2005, 24 (23): -4210 doi:
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[PDF 198 KB] (1064)

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Based on catastrophe theory，the relations among rock permeability，stress and strain in the whole test process are studied；and a cusp catastrophe model of relations among permeability，stress and strain of rock is established. Analysis of actual examples indicates that the model is appropriate to describe the relations among permeability，stress and strain.

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CONSTRUCTION OF IDEAL STRIKER FOR SHPB DEVICE BASED ON FEM AND NEURAL NETWORK

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2005, 24 (23): -4215 doi:
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[PDF 768 KB] (1310)

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In light of the three-dimensional effect of split Hopkinson pressure bar(SHPB) device for large diameter rock specimen，solid simulation is conducted with three-dimensional nonlinear dynamic finite element code；and the resultant data serials are then simulated with radial basis function (RBF) neural network and the ideal striker is self-adaptively recognized with the network. Finally，the constructed striker producing perfectly half-sine wave is compared with that back designed with one-dimensional stress wave theory；and it is demonstrated that the newly constructed striker by using three-dimensional nonlinear FEM and neural network has better half-sine waveform.

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NORWEGIAN EXPERIENCE IN SUBSEA TUNNELLING

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2005, 24 (23): -4219 doi:
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Subsea tunnels are located deeply under sea. Therefore，they are more difficult in geological investigation，design，construction and operation than land tunnels. In the last 30 years rich experiences have been gained in Norway from constructing 40 subsea tunnels and the“Norwegian subsea tunnelling concept”has formed. In the planning and design stage，careful pre-investigation is of critical importance. Extensive marine seismic refraction survey is the major method for investigating bedrock profiles and detecting fault，weakness zones and depressions，which are the major threats to the tunnel stability. Directional core drilling from onshore passes geological structures and obtains rock cores，therefore，direct evaluation of the rock conditions can be provided. Special rock support methods are needed in order to pass such weakness zones，including reduced blast rounds，bolt-enforced shotcrete rib and dense long spilling bolts. The lining of Norwegian subsea tunnels consists typically of sprayed concrete and rock bolts for support and free standing inner lining for water/frost protection. The lining is designed as a drained structure，sustaining no external water pressure. Cast-in-place concrete is used only in extremely adverse geological conditions. All subsea tunnels in Norway are excavated by drill and blast method. Inflow of sea water is one of the critical issues for subsea tunnels since there is no natural exit for the inflow water，and therefore，it is essential to know the geological and hydrogeological conditions ahead of face. Probe drilling and pre-grouting technique are the best ways to detect the water inflow and reduce it to the acceptable level. Even so，equipments and measures have to be ever ready to meet the emergency situation. The minimum rock cover is an influential factor to the tunnel stability as well as economy and should be evaluated carefully. A minimum rock cover of 23 m has been used，despite the Norwegian road tunnel standard requires more detailed geological investigation and special analysis if the minimum rock cover is less than 50 m. Problems related to in-leaking saline water，such as erosion of shotcrete and metallic parts，are special issues for subsea tunnels and need to be coped with seriously.

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EXPANDED COSSERAT MEDIUM CONSTITUTIVE MODEL FOR LAMINATED SALT ROCK

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2005, 24 (23): -4226 doi:
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A new expanded Cosserat medium constitutive model，in which the influence of bending was taken into account，was proposed for bilaminate-layered salt rock. In this model，a new unit cell，namely，the material point containing two alternate layers，was employed to simulate the coordination of the meso-displacement between two layers with mismatch mechanical properties. It was validated primarily by an experiment on laminated salt rock samples under uniaxial compression. This model provides a new way for the analysis of layered salt rock. Having the Cosserat stresses，namely，the macro-average ones，which have been determined，the conventional stresses of the different layers in a unit cell can be obtained in sequence. Then the conventional stresses can be utilized through a routine way for the strength and failure analysis. The proposed model can be expanded to solve three-dimensional and nonlinear problems directly，and is expected to provide a key theoretical frame for the stability analysis of the underground openings in laminated salt rock.

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STUDY ON RELATIONSHIP BETWEEN ROOF STABILITY AND TOP
COAL′S RECOVERY RATIO DURING CYCLIC WEIGHTING IN FULLY-MECHANIZED SUBLEVEL CAVING FACE

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2005, 24 (23): -4233 doi:
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[PDF 258 KB] (964)

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During cyclic weighting in fully-mechanized sublevel caving face，the stowing degree of the goaf influences the stability of hard and massive overlying roof. The course of top coal falling from begin to end is dynamic. To set up the judgment rules of roof stability with the top coal′s recovery ratio is an important theoretical problem. The mechanical model of the stability of the whole roof deformation and the part contact of the main roof is established. Based on the structure stability theory and the strength theory，two kinds of limited subsidence maintaining the stability of the whole deformation of roof structure and the stability of part contact of the main roof are gained. According to the comparison of the limited subsidence and the subsidence of roof brought about by the movement situation of roof in the course of rotation；the unified mechanical conditions between the stability of the whole transmutation of roof structure and the stability of part contact of the main roof are analyzed；and the judgment rules of roof stability with the top coal′s recovery ratio are established. Based on an example of fully-mechanized sublevel caving face，the judgment figure and method with the top coal′s recovery ratio are put forward；the theoretical bases of designing the safe top coal′s recovery ratio are provided according to different roofs，and the safe roof controlling is achieved at coal mine.

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SELF-ORGANIZED CRITICALITY OF GRANULAR MIXTURE AND
NONUNIFORM CELLULAR AUTOMATA

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2005, 24 (23): -4239 doi:
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At present it is universally considered that occurrence of self-organized criticality (SOC) relates to scale effect and organization principle. Scale effect bases on the sand-pile experiments performed around the world；but the organization principle hasn't been discussed ever. First，by means of the sand-pile experiment on a slope，it is discovered that self-organized criticality in granular mixtures is strongly influenced by the nonuniform degree of granular material. With the gradual increase of the nonuniform degree，the experiment presents the different phenomena and statistical results. Meanwhile，the dynamical behavior of granular material can transform from quasi-period to SOC and then to quasi-period again. Second，a cellular automata (CA) model that can describe the nonuniform property and embody the nonuniform coefficient is designed；i.e.，the value induced by friction is introduced as a token of different roughness of the sand pile surface. Adjusting the value of energy dissipation and the radius，experiments with different nonuniform coefficients and different scales can be simulated. By comparison the simulation results are similar to those obtained from the sand-pile experiment；it is found that they are similar and the organization principle is concerned with the robustness and the sensitivity of system. Only when the nonuniform granular mixture maintains the robustness and the sensitivity of whole system，it can break through the limit of scale；and the large-scale system remains self-organized criticality. Once the nonuniform coefficient continues to increase，the robustness dominates in the system and the sensitivity vanishes or weakens，the balance is broken，the nonuniform granular material can't show SOC. Finally，it can be achieved that the balance of robustness and the sensitivity is one of necessary conditions that make system show SOC.

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ELASTOPLASTIC FINITE ELEMENT IMPROVEMENT OF IMBALANCED THRUST FORCE METHOD

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2005, 24 (23): -4247 doi:
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[PDF 281 KB] (884)

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Connected with concrete engineering example of K111 debris landslide in Hangjinqu Expressway，it was investigated that how to combine mutually limit equilibrium method with FEM to be applied to analyzing slope stability and calculation of stability factor. Meanwhile，relationship between stability factor of slope and utilization degrees of the shear strength of sliding plane was also studied. The results are shown as follows：(1) the zone of plastic deformation and failure of slip-mass under approaching failure state can be obtained by the limit analysis method of elastoplastic FEM of slope stability；and then according to it，sliding plane of slope is determined；(2) it is shown that the sliding plane of slope determined by elastoplastic finite element limit analysis corresponds basically to the actual one revealed by field engineering geologic prospecting；(3) sections with different utilization degrees of shear strength are determined on the basis of plastic strain value under limit state of slope；(4)，it can calculate more accurately the stability factor of debris slope with imbalanced thrust method that comprehensively thinks over the different utilization degrees of shear strength of soil and rock on sliding plane； (5) it is proven by analyzing concrete example that to combine elastoplastic finite element with limit equilibrium method may be very well used to analyze the stability of debris slope and calculate its stability factor；it can reflect the actual state of slope more accurately. Therefore，it provides a reference to the stability analysis，evaluation and forecast of this kind of landslides.

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STUDY ON CREEP DAMAGE CONSTITUTIVE MODEL
OF SALT ROCK BASED ON MESOMECHANICS

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2005, 24 (23): -4253 doi:
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[PDF 188 KB] (1175)

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The damage behaviors induced by creep of salt rock are analyzed with creep experiments. A nonlinear creep constitutive model is given to represent the process of salt rock creep using correspondence principle based on mesomechanics. The model can reflect the characters of the difference between the model considering damage and that without considering damage，the strain rate increasing with the increase of effective stress；and the strain rate decreasing with the hydrostatic pressure.

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ANALYSIS OF DYNAMIC RESPONSE OF LARGE CROSS-SECTION TUNNEL UNDER VIBRATING LOAD INDUCED BY HIGH SPEED TRAIN

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2005, 24 (23): -4259 doi:
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[PDF 441 KB] (1383)

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With the development of high speed railway，more and more attentions have been paid to the effect of vibrating load induced by high speed train on large cross-section tunnel. Based on the numerical simulation of vertical vibrating load induced by high speed train with excitation function，dynamic response of large cross-section tunnel under the vibrating load has been analyzed by elastoplastic finite element method；and the effects of different section forms，train speed and damping ratios on the dynamic response are also studied. Comparisons of dynamic responses between large cross-section tunnel and general one are performed.

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STUDY ON A NEW BACK ANALYSIS ALGORITHM IN
GEOTECHNICAL ENGINEERING BASED ON IMMUNIZED
CONTINUOUS ANT COLONY ALGORITHM

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2005, 24 (23): -4266 doi:
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[PDF 266 KB] (1004)

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To solve the optimization problem in back analysis of geotechnical engineering，the global optimization algorithm，such as evolutionary algorithm，is a very good method. But the efficiency of this algorithm is a very large defect. In order to overcome the defect of those optimization methods，a new algorithm—immunized continuous ant colony algorithm(ICACA) based on the traditional continuous ant colony algorithm(CACA) and the principles of immunized artificial system(IAS) is suggested for the first time. Combining ICACA with FEM，a new back analysis algorithm is proposed. Through a simple example，the validity of the proposed algorithm is verified；and the results show that this new algorithm is a very good method for back analysis and its efficiency is high.

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SIMULATION OF LOESS BEHAVIOURS UNDER CYCLIC LOADING

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2005, 24 (23): -4272 doi:
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[PDF 738 KB] (1046)

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Under undrained conditions，the phenomena of strain softening occur when the loess taken from northern France is subjected to monotonic loading，while liquefaction or cyclic mobility phenomenon is observed under cyclic loading. The bounding surface model and the generalized plasticity model are used to predict this behaviour. It is shown that the accumulated rate of plastic strain under cyclic loading is slower than that in softening region under monotonic loading. The sensitivity of model parameters is discussed；and it is concluded that both the bounding surface model and the generalized plasticity model can describe the loess liquefaction satisfactorily，provided that appropriate parameters are defined.

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PROBABILISTIC VOLUME ELEMENT MODELING
IN ELASTIC DAMAGE ANALYSIS OF QUASI-BRITTLE MATERIALS

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2005, 24 (23): -4282 doi:
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[PDF 473 KB] (1301)

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To determine the underlying probabilistic distributions of the physical and mechanical property parameters of the mesoscopic representative volume element (RVE) and to form the probabilistic volume element (PVE) models，it is a quintessential problem in the elastic damage analysis of quasi-brittle materials by means of the damage micromechanics. In particular，it is the theoretical basis of initializing the heterogeneous material properties in the famous finite element micromechanics code，rock failure process analysis (RFPA). The RFPA code and its embedded PVE model based on the Weibull distribution are introduced briefly first. Then other two historical studied PVE models based on the quasi-Weibull distribution and the normal distribution in the theoretical research for building the RFPA code are also described briefly. After the discussion and review of these PVE models in detail，a PVE model based on lognormal distribution is proposed to improve the simulation of the heterogeneity of quasi-brittle materials and to provide an alternative type of PVE model for the RFPA code. The rationality that the heterogeneity of rock-like materials is able to be described by the lognormal distribution is proved by the uncertainty analysis of the influencing factors of material properties. The lognormal PVE model is compared with these three PVE models and is verified with the complete stress-strain curves of various rocks obtained in the laboratory simply uniaxial tests. Comparisons and verifications show that，similar to Weibull distribution，the proposed lognormal distribution is suitable for the PVE modeling and agrees very well with the elastic damage constitutive relationship of quasi-brittle materials. This research also provides a circumstantial evidence that it is reasonable to use Weibull distribution in the PVE modeling and the RFPA code. In the PVE modeling in the statistical elastic damage analysis of quasi-brittle materials，lognormal distribution is an alternative choice besides Weibull distribution，but the normal distribution and the quasi-Weibull distribution should be excluded.

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STUDY ON NORTHWARD DEFORMATION MECHANISM OF CENTRAL PIER OF PERMANENT SHIPLOCK OF THREE GORGES PROJECT

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2005, 24 (23): -4289 doi:
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Northward deformation is monitored during the excavation period with various devices installed on the surface and inside the rock mass of the central pier between the double chambers of the permanent shiplock of the Three Gorges Project in China. In terms of the fundamental understanding of rock deformation for such a slope in hard rock，the northward deformation is believed to be linked to local factors such as presence of north-dipping geological structures in the pier，excavation and support sequences during the construction period. In details，the advanced proceeding in the north chamber in the early excavation stage did result in the northward deformation in general，but at a small magnitude with a few millimeters，thus it was not the major factor causing the occurrence of the northward deformation. With the proceeding of excavation to greater depths in the middle stage，dominant north-dipping geological structures started to play an important role in the northward deformation. In the later stage，the reinforcement on the potentially instable rock blocks controlled by the northward structures transfers partial loads to the southern rock mass simultaneity，which turns to be the main factor that induces the northward deformation. Based on the discontinuous mechanics，a three-dimensional distinct element code(3DEC) model was accordingly established and numerically validated the northward deformation.

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STUDY ON SPATIAL PREDICTION METHOD FOR REGIONAL
LANDSLIDES AND RESULTS ANALYSIS

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2005, 24 (23): -4297 doi:
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[PDF 485 KB] (1142)

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The aim of spatial prediction for regional landslides，mainly by analyzing the rule of historical landslides distribution，is to point out the regions that are relatively dangerous. On the basis of MAPGIS software and its customizing，two methods，semi-quantitative and quantitative one，are adopted to forecast regional landslides in Yongjia County of Zhejiang Province. In semi-quantitative method，the harassing coefficient reflecting the intensity of historic landslides and the susceptible index are used to evaluate regional landslides；and hazard zoning map is obtained. In the quantitative method，information value model and method of regular grid are adopted to predict regional landslides. Then，the hazard zoning map is compiled by the results of the information value，which provides scientific references for decision-making about land planning and buildings construction for local government. At the same time，by the results of two methods，the relationships between landslide formation and influential factors are analyzed so as to make landslides prevention feasible.

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QINGHUA MODEL REVISED BY SMP CRITERION

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2005, 24 (23): -4303 doi:
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Spatially mobilized plane(SMP) criterion is one of the most famous failure criteria in the field of soil mechanics when describing characteristics of soil under the three-dimensional stress condition，while Qinghua model is one of the most famous domestic constitutive models. It′s aimed to combine SMP and Qinghua model using a transformed stress tensor based on the SMP criterion. Thus the Qinghua constitutive model whose failure and yield criterion is SMP instead of Mises yield criterion. Using this method，it can be computed without even increasing original model′s parameters. And this method realizes the consistency from the shear yield to the shear failure with the SMP criterion. The revised Qinghua model is able to describe the behavior of soils in general stress condition including triaxial compression.

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CENTRIFUGAL MODEL TEST ON SLOPE STABILITY
OF LEVEE PROJECT

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2005, 24 (23): -4308 doi:
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[PDF 186 KB] (1019)

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The safety factors of levee project under the conditions of completion，the water level fall suddenly and the high water level should be analyzed in the designs. The methods of simulating model material，operating mode and test technology in the centrifugal model tests for above-mentioned conditions are given，and the methods of getting safety factors from the ruinous centrifugal model tests are discussed. All these are important to analyze the work mechanism and to optimize the design in the levee project.

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PHYSICO-MECHANICAL PROPERTIES CHANGES OF QINGHAI—TIBET CLAY DUE TO CYCLIC FREEZING AND THAWING

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2005, 24 (23): -4313 doi:
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[PDF 289 KB] (1395)

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A fine-grained clay was compacted in the laboratory and was thereafter exposed to a maximum of 21 closed-system freezing and thawing cycles. The sample height，water content，stress-strain behavior，failure strength，elastic modulus，cohesion and internal friction angle were measured in unfrozen soil as well as in thawed soil. The results show that the physio-mechanical characteristic of investigated soils changed after freezing and thawing. The height of studied sample increased and water content decreased before 7 freezing and thawing cycles and kept invariable after 7 freezing-thawing. The curves style of stress-strain behavior were not be affected by freeze-thaw process；but the elastic modulus and failure strength were heavily influenced by the number of freeze-thaw cycles. For the soil investigated，the cohesion decreased with increasing of the number of freeze-thaw cycles；and the internal friction angle ranged from 15°to 30°.

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MECHANISMS OF PROPERTY CHANGES OF SOFT CLAYS AROUND DEEP MIXING COLUMN

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2005, 24 (23): -4320 doi:
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Installation of displacement types of columns such as driven pile，sand compaction pile，lime compaction pile，and deep mixing column causes stress changes in the surrounding soil. The properties will change in surrounding soil. Strength of the surrounding soil will decrease，recover，and increase after column installation. The mechanisms of effects of deep mixing column installation on surrounding clay can be identified into seven categories：(1) disturbance or structure damage of soil surrounding the column due to blade mixing and expansion of admixture injection；(2) thixotropic behaviour of soft clay；(3) soil fracturing around column during mixing and expansion；(4) cement penetration and diffusion from column to surrounding soil through fractures and soil pores；(5) cementation due to increase of cation concentration in pore water；(6) consolidation effect due to increase of effective stress in surrounding soil after excess pore pressure dissipation；(7) heating caused by the chemical reaction of hydration and pozzolanic reaction. These influential factors were investigated through laboratory tests and theoretical analysis. Laboratory tests were performed to investigate the effects of soil thixotropy，soil fracturing，and cement penetration in soft Ariake clays. Theoretical analysis was employed to analyze the fracturing phenomenon. Fractures and cement penetration phenomenon were observed in laboratory test. For soft Ariake clay，test results show that strength due to thixotropic hardening regained completely within 70 days. Theoretical result shows that even in a very low admixture injection pressure，fracturing will occur in surrounding soil.

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FRACTURE MECHANICS ANALYSIS OF ROCK BRIDGE
FAILURE MECHANISM

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2005, 24 (23): -4328 doi:
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Rock bridge fracture among multi-crack is one of the important reasons for rock mass failure. If the crack distribution near a rock bridge is known，it is the prerequisite to predict or refrain the failure of this kind of rock mass that the patterns，mechanism of failure and loading conditions are foreknown. These can be essentially obtained by the distribution analyses of the stress and strain extreme values near the crack tips according to the theory of fracture mechanics. The main result is that when the directions of the extreme values of two adjacent cracks are nearly towards each other，these two cracks will link together definitely and result in the rock bridge failure. The properties of the two extreme values determine the properties of the rock bridge fracture.

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CONTINUOUS-DISCONTINUOUS METHOD FOR FAILURE
PROCESS OF CONCRETE BEAM

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2005, 24 (23): -4335 doi:
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[PDF 395 KB] (953)

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Using finite element shape function as partitions of unit，the displacement jump across a crack is represented by extra freedom degree of enriched node. Continuous-discontinuous displacement model allowing the displacement of internal element discretion is developed. The expansion path of discontinuouos displacement is completely independent of the mesh structure. Unlike so-called embedded enhanced discontiniuity model，which is based on incompatible strain，there is no restriction on the type of underlying solid finite element that can be used；and displacement jumps are continuous across element boundaries. Physical concept of the model is also different from that of the extended finite element method. Combined with cohesive crack model，the effectiveness of the proposed approach is demonstrated by simulating the fracure process of concrete beam under shear loads.

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DISPLACEMENT BACK ANALYSIS OF ARCH DAMS BASED ON IMPROVED GENETIC ALGORITHM

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2005, 24 (23): -4341 doi:
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The improved genetic algorithm is proposed to identify the elastic constants of rock foundation of concrete arch dams according to the measured displacements. Considering the premature phases of genetic algorithms，niche technology and method of adaptive probabilities of crossover and mutation are both introduced into the classical simple genetic algorithm to carry out the displacement back analysis which is based on the displacements measured in the model experiments and 3D FEM. In a case study on the practical engineering，the elastic modulus and Poisson′s ratio are obtained. The study shows that this method is suitable for the displacement back analysis of arch dams. It can also avoid premature phases that often happen in simple genetic algorithms，and a good convergence is achieved.

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MODEL EXPERIMENTAL STUDY ON STYLE OF STRUCTRUAL
INTERNAL FORCE AND STABILITY OF SURROUNDING ROCK IN
DOUBLE-ARCH TUNNEL

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2005, 24 (23): -4346 doi:
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The large-scale model testing is one of the important methods to research style of structural internal force and stability of surrounding rock in double-arch tunnel. Based on the Xiaojinkou double-arch tunnel engineering of Guangzhou—Huizhou Expressway，the construction method，styles of structural internal forces and the stability of surrounding rock of double-arch tunnel are studied in detail under the condition of surrounding rock types II and III. By the model testing，a new method，i.e.，central-heading expanding method，has been suggested. The surrounding rock is seldom disturbed when the tunnel is constructed by the central-heading expanding method. The three-heading method，double-heading method and central-heading expanding method have been studied by model testing. It is found that the maximum radial displacement take places at the arch and the sidewall. The model of internal force for the secondary lining and the laws of the deformation and the stability for the surrounding rock have been set up firstly in the double-arch tunnel. The results can offer references to the design and construction of double-arch tunnel.

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DYNAMIC RESPONSE OF SOIL IN SATURATED HALF SPACE UNDER
MOVING LOAD

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2005, 24 (23): -4352 doi:
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The dynamic response of soil in saturated half space under moving load is analyzed by semi-analytical method. Soil is regarded as a kind of homogeneous，fully saturated elastic medium. Based on Biot dynamic consolidation equation，by using Fourier series expansion，the partial differential equations are transformed into ordinary deferential ones and solved. The responses of soil in saturated half space under moving loads are obtained，and the variation of responses of soil with different parameters is discussed.

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MECHANISM AND SETTLEMENT ANALYSIS OF PILE-SUPPORTED AND GEOGRID-REINFORCED EMBANKMENTS

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2005, 24 (23): -4358 doi:
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As an effective and economical treatment for soft soil，pile-supported and geogrid-reinforced embankment has been used widely in the world. In the numerical analysis，subsoil and embankment treated by one pile are simplified as a circular column；distribution characteristics and dissipation process of the initial excess pore water pressure under instantaneous loading are analyzed using elastoplastic FEM considering consolidation process of the subsoil. Mechanical properties of geogrid and settlement of embankment are also studied. The influences of pile length，pile space and pile cap dimension on load sharing ratio of pile and embankment settlement are also investigated. It can be seen that the initial maximum pore water pressure takes place in the lower soil due to the load transformation from pile cap to soil. When the pile penetrates the soft soil，the settlement of embankment is dependent on the compression of upper soil between the piles. Otherwise，embankment settlement lies on the compression of soil beneath pile. Pile length is the main factor that effects the settlement of embankment；pile space and dimension of pile cap are followed. A case study is performed at last.

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STUDY ON TWO TYPES OF TECHNIQUES OF SHEAR WAVE VELOCITY TEST FOR SOIL SPECIMEN

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2005, 24 (23): -4368 doi:
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Torsion shear wave transducer is a newly developed device to test the shear wave velocity of soil specimen which has not been reported before. Parallel shear wave velocity tests are carried out on cohesive and cohesionless soil specimens by using torsion wave transducer and another method，bending element method，separately. The results show that test results by the bending elements are 20 percent lower than that obtained from torsion wave transducer for the same kind of soil specimen under the same consolidation condition. To check which device is more reliable，another test is performed in which the shear wave velocity of plexiglass rod，whose true shear wave velocity is known，is tested with torsion wave transducer，and the test result has only 1.2% relative error to the real value，which means that the torsion wave transducer is a more reliable shear wave velocity test device.

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NUMERICAL SIMULATION FOR COMBINED BREAKING ROCK WITH HIGH PRESSURE WATER JET AND MECHANICAL BIT

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2005, 24 (23): -4373 doi:
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According to practical working situation，nonlinear dynamic finite element method is adopted to establish a numerical model of combined breaking rock with high pressure water jet and mechanical bit. Breaking process of rock with high pressure water jet is studied；and two critical pressure concepts are put forward. The conclusion that rock breaking process under high pressure water jet is divided into hammer impacting break and erosion break is proven by experiment to be true. Conclusions can be drawn from calculation results that the efficiency of the combined breaking rock is about 2 times as much as the summation of high pressure water jet and mechanical bit separately breaking rock；and the best distance between water jet and bit is about 13 mm. When the pressure of jet is high enough，the efficiency of breaking rock will be increased if rotation speed improves. Dropping down the drilling pressure properly to a certain value will not affect the efficiency of breaking rock. Hydrostatic pressure reacts on the efficiency of breaking rock.

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ANALYSIS OF BEDDING LANDSLIDE OF CUTTING SLOPE
IN AN EXPRESSWAY AND ITS TREATMENT

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2005, 24 (23): -4383 doi:
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In segment of K90+900–K910+080 at Xiangtan—Shaoyang Expressway，there are two sub-first grade faults which intersect obliquely with roadbed. A plentiful intersectant joints which are about vertical，along-slope clay shale，and bad coal seams exist in the rock mass in the upper mountain，which are intrinsic factors that induce landslide. The maximum depth of cutting slope is about 30 m. After the cutting slope is excavated，the shear resistance of soft rock seam falls because the surface water infiltrates through the top rock joints into it，and therefore，landslides take place probably. Simplified Bishop method is adopted in landslide calculation. The shear strength parameters of slide seam are drawn out that the internal friction angle j =11.5° and the cohesion c= 8.2 kPa by back analysis and experience analogy. If the rock bolts or anti-slide piles are just adopted without cutting-slope unloading in the treatment，the treatment will be very expensive. Therefore，the main measures adopted for cutting-slope unloading are put forward in the first landslide treatment scheme. In construction，top cracks are not blocked and drainage system is not set up in time，the shear resistance of slide seam constantly falls because the water in the slide seam is not easily drained away；and lead the slope to slide constantly. Based on further calculation and analysis，long rock bolts and other waterproof drainage facilities are presented in additional treatment scheme. The landslide has kept stabilization for three years since the treatment measures were taken.

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ANALYSIS OF THERMAL STATE UNDER PARTICLE REFORMATIVE ROADBED IN QINGHAI—TIBET RAILWAY

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2005, 24 (23): -4390 doi:
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Based on observed data of particle reformative roadbed，normal roadbed and natural ground in Beiluhe test site of Qinghai—Tibet Railway，the characteristics of underlying ground thermal regime of three modes are quantitatively analyzed. Results indicate that the endothermic quantity of constructing embankment is greater than that of natural field. The thaw period of particle reformative roadbed is longer than that of natural field，but less than that of normal roadbed. By contrast with natural ground，the thermal exchange of the particle reformative roadbed is almost equal to natural ground according to thermal exchange state. The exothermal intensity is greater than the endothermal intensity. It entirely presents exothermal state. The thermal exchange state can be restored by using the particle reformative roadbed. It takes on the effect that the particle reformative roadbed can protect frozen soil and it is also an effective way to actively protect frozen soil.

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THREE-DIMENSIONAL SIMULATION STUDY ON LAW OF DEFORMATION AND BREAKAGE OF COAL FLOOR ON
MINING ABOVE AQUIFER

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2005, 24 (23): -4396 doi:
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The similarity theory on coupling of solid and liquid is put forward；and a part of type simulation material has been made. The similarity modeling resemble simulation experiment equipment of 3D coupling on solid and liquid is originated；and the loading system，testing system，mining system，flow area simulation and its testing system have been perfected. Then，using the 3D solid-liquid coupling simulation bedstead，the law for deformation and breakage of coal floor on mining above aquifer of Dongshan Colliery，Taiyuan，has been studied. The law of deformation and the breakage of coal floor vary with coal mining are discussed. The stress and deformation of coal floor are changed dynamically. And the varying frequency，the range of stress and deformation have been analyzed. It provides theoretical foundation for coal mining above aquifer.