Beishan granite is a typical quasi-brittle rock and its material degradation and structure failure is mainly attributed to the inelastic deformation and the damage development due to microcracks. This paper is devoted to modeling the nonlinear mechanical behaviors of Beishan granite. A damage-friction coupled model was developed based on the method of linear homogenization and the irreversible thermodynamics. The granite was viewed as a heterogeneous material composed of the matrix and a large number of randomly distributed microcracks，and thus our studies started with a representative elementary volume(REV)，i.e. the matrix-cracks system. The free energy of the REV was determined with Mori-Tanaka method and the thermodynamic forces associated with the inelastic strain and the damage variable were derived. The development of the inelastic strain and the damage were determined with the criterion of associated general Coulomb friction and the damage criterion of rate-based strain energy release respectively. An explicit function of the rock strength was derived during the damage-friction coupled analyses. The essential feature of the damage resistance function was described. The proposed multiscale model was finally applied to simulate a series of triaxial compression tests on Beishan granite. The comparison between the numerical predictions and the experimental data validated the model and showed outstanding advantages of the multiscale constitutive formulations over the phenomenological models.

The uniaxial compression tests on red sandstone samples with two non-coplanar fissures after the heating of high temperatures(the sample size is 80 mm×160 mm×30 mm) were carried out with a servo-controlled testing system of rock and acoustic emission(AE) equipment to investigate the effect of high temperature on strength，deformation and crack behavior. With the increase of temperature，the peak strength，the elastic modulus and the deformation modulus of red sandstone with two non-coplanar fissures were found to increase initially and then to decrease with the maximum value occurred at 300 ℃. However，the peak strain of  the tested specimen increased nonlinearly with the increasing of temperature. Pronounced AE events occurred whenever the stress drops occurred，which corresponds to the initiation or coalescence of cracks in red sandstone samples. The effect of high temperature on the evolution of cracks was analyzed with the photographic measurement. It was found that，with the increase of temperature，the stress at crack initiation increased firstly and then decreased with the maximum value occurred at 300 ℃. However，the stress at crack coalescence increased from the room temperature to 600 ℃ and then changed little when the temperature varied from 600 ℃ to 900 ℃.

The structure and strength of fractured rock mass are different from those of soil，so the existing theory for frozen soil is not applicable to the problems of crack initiation，propagation and network development in rock mass under low temperature. The moisture migration and the pressure due to frost heaving in freezing-thawing process and the crack propagation after freezing-thawing process have been the key issues. The research on the mechanism of moisture migration should be based on the micro-scale and more attentions should be focused on the flow characteristics of unfrozen water film considering ice segregation. The damage degree of fractured rock under freezing-thawing is directly affected by the frost heaving pressure. However，the frost heaving pressure and crack extension are affected by many factors，such as the crack shape and the spatial position，the unfrozen-water content，the freezing temperature and the rock properties. During the last several decades，the efforts have been focused on the investigation of the extension of frost cracks with theoretical analysis，laboratory tests and field monitoring. Although remarkable achievements have been obtained，research on freezing fractured rock at present is far from mature. In order to reveal the mechanism of damage development of fractured rock mass under freezing-thawing，future studies should be based on the investigation of water migration in fractured rock mass with laboratory tests and the establishment of calculation method of frost heaving pressure. Then，the influence of frost heaving pressure on the development of fracture network can be studied combined with the criterion of crack extension.

Laboratory experiments were carried out to study the particle segregation of rock fragments during the movement of debris avalanche. The influence of small particle contents，size differences and bed roughness were considered during the experimental process. Experimental results showed that the degree of segregation was greatly influenced by the size difference of particles and was less sensitive to the content of small particles. The particle segregation became more obvious with the increasing of the roughness of sliding bed. The formation mechanism of inverse grading during the movement of landslide was studied based on the field investigation，physical modeling tests and past studies. During the process of high speed landslide，the energy loss(relatively) of small particles was found to be larger than that of large particles，the segregation phenomenon of the larger particles in front of the small particles at the movement direction existed. After the debris avalanche entered into the stage of deceleration and accumulation，the small particles were stopped earlier than the large particles，resulted in that the large particles were moved on top of the deposits of small particles，while most of the small particles were blocked at the end of the landslide deposits. Finally，the inverse grading structure of landslide deposits was formed，where most of the larger particles were at the front of landslide deposits and most of the small particles were at the rear of landslide deposits，while the larger particles stay on top of the small particles at the middle section.

Because of super mobility，high velocity and enormous energy，the landslide-debris flow is a kind of geological disaster with extreme destructive power. In order to simulate three-dimensional movement of landslide-debris flow，a simulation model considering the erosion effect and the change of friction resistance at the bottom of landslide was established in the paper based on the local Lagrange coordinate system and the finite volume method. The simulation model was validated with the example of El Picacho landslide using the parameters of distance erosion rate and Voellmy model. The results of simulation showed that the runout path and distance agreed with the field data of measurement，which indicated the effectiveness of the proposed model. Besides，the simulation without erosion effect was carried out. It is indicated that the total volume of sliding mass was decreased and the runout distance was shortened，which indicating that the erosion effect at the bottom of landslide was an important factor for the movement of landslide-debris flow.

Contact retrieval algorithm is one of the key factors to guarantee the computational efficiency and accuracy in three-dimensional discontinuous deformation analysis(3D-DDA). Based on the idea of the direct method and the common plane(C-P) method，the algorithm searching the block contacts was improved by transforming all the contact types into two basic ones，the vertex-face contact and the edge-edge contact using the bounding box outside the block，the block cutting surface and the contact inheritance. The probe to the movement of block corners was firstly introduced to identify the correctness of the contact which overcome the weakness of the existing contact algorithms without considering the movement trend of blocks. The algorithm was implemented in a three-dimensional analysis block software TJSG. The results of the examples indicated that the algorithm exhibited good adaptability and robustness for both the convex and concave blocks.

The deformation of tunnel at early stage is of critical importance to determine the support pressure and stable deformation of rock mass using the convergence-confinement method. Some typical formulae of displacement release coefficient for deep circular rock tunnels were summarized，classified and compared in terms of the applicability and the spatial effect of tunnel face. The differences from the convergence-confinement analysis due to the different coefficients of displacement release，different positions of support installing and different control objectives were discussed. It was found that the coefficient of displacement release dependent on the ultimate plastic radius of rock mass was applicable to both the elastic and the elasto-plastic rocks and therefore had wide prospects of engineering applications. The coefficients of elastic displacement release were found to be only applicable to the elastic rock，while the commonly used coefficients of plastic displacement release were only suitable for the rock tunnel with a normalized radius of 2. The support designed according to the support pressure distant from the tunnel face could not be moved forward arbitrarily and a reasonable and timely support with different stiffness should be designed according to the properties of rock mass.

Based on the theory of particle flow and the particle flow code(PFC)，an equivalent crystal model reflecting the mesoscopic structural features of rock mineral was established with the combination of models of bonded particles and smooth joints. The suitability and reliability of the equivalent crystal model of rock were validated with the experimental and calculated data. The mechanism of fracturing and the strength of rock under loading condition were revealed from mesoscopic viewpoint. Under the uniaxial tensile condition，the surfaces of macro fractures were found to be approximatively perpendicular to the loading direction and the fractures were primarily due to the tensile failure of bond on the boundary of crystalline. Under the uniaxial or triaxial(low confining pressure) compression，the surfaces of macro fractures were parallel to the loading direction and the fractures were primarily due to the tensile failure of bond on the boundary of crystalline，which led to the splitting failure of rock macroscopically. Under the triaxial compression with the high confining pressure，the surfaces of interpenetrating macro fractures cross oblique to the loading direction were primarily due to the tensile failure of bond in the crystalline，and the tensile and shear failure of bond on the boundary of crystalline，which led to the macro shear failure of rock. For hard brittle rock such as granite，the lower ratio between the tensile and uniaxial strength of the rock，can be reproduced by adopting the equivalent crystal model，and its strength properties can be reasonably described with Hoek-Brown strength criterion.

In order to study the influence of water on the mechanical properties of granite from Western Liaoning，the deformation and fracture of the granite were investigated with the mechanical test system of rock MTS–815. The effective peak intensity，volumetric dilation，residual strength，post-peak intensity and parameters of the granite were analyzed under different confining pressures and pore water pressures. The reduction factor of the effective peak strength was found to increase linearly with the increasing of pore water pressure and the slope of the linear relationship was reduced gradually with the increasing of confining pressure. When the confining pressure was smaller，the influence of the pore water pressure to the reduction factor of the effective peak strength was clearly notable. When the confining pressure was larger and the pore water pressure was smaller，the effect of pore water pressure was suppressed because the pore throat was compressed under the condition of applied stress. The starting point of volume expansion was found to be the characteristic point of enhanced water effect in dense rock. The confining pressure delayed the occurrence of expansion，while the pore water pressure promoted the occurrence of expansion. The volumetric dilation and water effect promoted each other. The residual strength under water effect is about 21% to 35% of the peak strength without water effect. Hoek-Brown constant increased nonlinearly with the increasing of confining pressure，and its value was between 3.5 and 5.0. At the post-peak stage of stress-stain curve，the change of pseudo internal friction angle was found to be small. The pseudo cohesion decreased with the increasing of strain softening coefficient，and it decreased with the increasing of pore water pressure when the strain softening coefficient was the same. The cubic spline surface was used to describe the relationship among the generalized cohesion，pore water pressure and strain softening parameter.

Assessment of landslide hazards often requires good knowledge of the moving characteristics of landslides. However，the current analysis is mainly based on qualitative models，which are not suitable for quantitative analysis. To overcome this shortcoming，a three-dimensional model of spring-deformable-blocks was formulated to produce the motion of landslides. The motion of landslides was assumed continuous and variable，and the sliding body was divided into a number of deformable columns. With the force acting on the side face of columns，the deformation of the column was obtained according to the relationship of force-deformation of sliding body. The formulas for the acceleration，velocity and displacement of sliding body were established considering the accumulation and the release of the deformation energy. The proposed model was implemented in a program based on Visual Basic for the visualization of the motion of landslides. The program was applied to analyze the sliding time，the maximum velocity and the displacement of the sliding body of Jiweishan landslide in Wulong， Chongqing. The results from the simulation was found to be in good agreement with the existing numerical results.

The creep strain from the creep tests under triaxial cyclic loading was separated into the viscoelastic and the viscoplastic strain and the rheological models were established accordingly to describe the variation of creep in the attenuation and steady stages. To describe the accelerated creep stage，a damage factor was introduced into the viscoplastic rheological model. As a result，a modified viscos-elastic-plastic creep model was established. The sensitivity of parameters of the model was analyzed. The creep experiment under triaxial cyclic loading on coal with various deviatoric stress levels was carried out and the elastic and plastic strains of coal were analyzed separately. Comparisons between the results obtained from creep model and creep tests showed that the proposed model described the overall rheological deformation of coal under cycle unloading path.

The aims of this study were to quantitatively measure the spatial distribution structure of regional landslides，to reveal the differences and causes of distribution patterns between regional landslides of different sizes. The diameter of a landslide was graded into classes(scales) according the data from the database of Loess landslides. The spatial distribution structure and causes of loess landslides on various scales of diameter were quantitatively analyzed with the methods of the correlated fractal dimension，the kernel density and the GIS spatial analysis. The loess landslide with the diameter within the scale of 50–75 m occupied the maximum proportion，comprising 28.87% of the total landslides. The landslide on the scale larger than 100 m was the least which accounted for 15.12%. The spatial structure of landslide on various scales had multi-fractal characteristics. There was a distinct inflection point on the scale of 30 km. On the scale smaller than 30 km，the correlated fractal dimension was raised with the increase of diameter scale，and the distribution pattern was turned from the aggregation into the dispersion pattern gradually. On the scale larger than 30 km，the distribution of regional landslide exhibited an aggregation pattern. The loess landslides were mostly affected by topography and landforms during its process of development. Among selected 3 major factors influencing the distribution patterns，the distance to river stream was the most influential factor followed by the relief amplitude. A higher proportion of the landslide with small diameter scale was found to take place near the stream with smaller relief amplitude. However，a larger proportion of the landslide with large diameter scale occurred at the places with larger relief amplitude and far away from river. Slope had negligible effect on the distribution pattern.

Data from geological map，outcrop and borehole were utilized for the reconstruction of geological surfaces of complex 3D geological body. Detailed analysis of core issues in 3D reconstruction of geological interfaces was conducted including the interfaces determination，3D interpolation，geometric modeling and evaluation of reasonableness. A method of geological interfaces reconstruction was proposed based on the evaluation of geological cause of formation. This method integrated the complex and diverse geological data better and determined the complex geological interfaces more rationally and efficiently. Therefore，the method made 3D reconstruction of the geological interface more intelligently as a result of reduction of human intervention，which was verified and demonstrated in an example of engineering application.

A discrete element model(DEM) of describing the equivalent strength of coal mass after cracking due to the coupled action was established for the quantitative evaluation of the effect of cracking due to coupled action. The overall strength was taken as an index to achieve the equivalent transformation of discretization of intact to loose coal mass. The caving of the top coal and the flow pattern were researched with DEM. The hinge relationship of discrete particles and its influence to caving after coupled cracking were analyzed. The relationship between the caving and flowing capacity of coal mass，the parameters of explosive load and the injecting pressure of water was quantified and the result was verified in an engineering practice. The essence of coupled cracking was the spreading of the gas and blast wave generated in the explosion in the softened coal-rock. The overall strength of coal-mass was regarded as an equivalent conversion index for the equivalent transformation between the different algorithms for coal-mass. The method of coupled cracking increased the caving effect of coal-mass by reducing the tensile stress of blocks and the amount of contact between particles. The strength of coal mass for fully caving and the peak strength meeting the requirements of recovery ratio for the thick coal seam were obtained. The quantitative assessment of coupled cracking in coal mass under the complex environment was accomplished.

Shear strength of geomaterials including cohesive strength and frictional strength is significantly influenced by the hydrostatic pressure. The shear strength is provided by cohesive force，frictional force between granules and the crush of granules. Roles of cohesive strength and frictional strength played under different hydrostatic pressures were analyzed，and the shear strength property influenced by the crush of granules was also studied，then the mechanism of hydrostatic pressure effect was expounded. When the material was under a low hydrostatic pressure，the mutual movement of granules resulted in the failure of geomaterials，which exhibited the shear stress ratio failure characteristics. When the material was under a high hydrostatic pressure，the crush of granules resulted in the failure of geomaterials，which exhibited the shear stress failure characteristics. The failure function in meridian plane of triaxial compression was used to revise the nonlinear unified strength model. The revised nonlinear unified strength model described not only the effect of intermediate principle stress，but also the effect of hydrostatic pressure on geomaterials more reasonably. Compared with the data from a number of true triaxial tests，the revised nonlinear unified strength model was shown to describe well the hydrostatic pressure effect and 3D nonlinear strength properties under multiaxial stress conditions of different materials.

In this study，ground surface displacements and horizontal movements of deep soils associated with shield tunnelling were derived on the basis of the elastic Mindlin?s solutions. The pressures induced by the compressing effect of cutter-head，the non-uniform distribution of softening skin frictions along the shield in soft soils，the grouting pressures at shield tail and the soil movements caused by soil loss were considered in the proposed solution. This method was verified against three case histories and good agreement was achieved between the predictions and measurements，showing that the method was able to capture the tendency of soil movements induced by shield progressing. The shield construction was found to be responsible for the ground heave in front of the shield face and the distribution of heave resembled a normal distributed curve. High grouting pressure at shield tail was found to be another cause of the ground heave. The deep soils in the transverse direction of shield advancing were compressed during shield progressing and moved away from the center line of shield. The maximum horizontal soil movement occurred near the center line of the shield.

A series of undrained cyclic tests under consfant/variable confining pressures were carried out on typical Wenzhou soft clay by GDS cyclic triaxial apparatus. The coupling effect of cyclic deviatoric stress and cyclic confining pressure on the undrained permanent deformation of overconsolidated saturated soft clay was studied. Under the undrained condition，the cyclic confining pressure was found to limit the development of the permanent axial strain of overconsolidated saturated soft clay to some extent. The permanent axial strain reduced 20.18% if the ratio of p/q was raised value of 1. On the basis of the experimental results，an empirical formula incorporating the effect of overconsolidation ratio and cyclic confining pressure was proposed to estimate the permanent axial strain in the undrained cyclic tests.

In order to analyze the ground vibration induced by the high-speed train，a simplified analytical solution of the moving train load considering the geometric irregularities of track was derived and the flexibility matrix was derived based on 2.5D finite element method. Then，using the load derived above as the input，a train-track-foundation model was established，and the influence of geometric irregularity on wheel/rail force was calculated. If the wavelength and speed were kept constant，the greater the amplitude was，the greater the ground vibration and the greater the wheel/rail force. If the amplitude and speed were kept constant，the longer the wave length was，the smaller the foundation vibration and the smaller the wheel/rail force. If the wavelength and amplitude were kept as constant，the greater the speed was，the more intense the vibration.

The dynamic compaction with low energy was considered to deal with the problems of the increasing of the electrical resistance of soil samples due to cracking and of the interface between anode and soil，the increasing of energy consumption and the decreasing of the effect of consolidation due to anode corrosion in the electro- omostic process，and in the extreme cases the interruption of the electro-osmotic process. Indoor model tests of electro-osmosis with and without the low-energy dynamic compaction were carried out respectively. The low energy dynamic compaction was found to improve the drainage paths of the soil and the water drainage was increased than that without dynamic compaction. The electrical circuit current was increased and soil compactness was enhanced due to low-energy dynamic compaction. The cracks in soils ample was closed，the surface settlement was increased，and the uneven settlement of soil and the anode corrosion were reduced due to the low-energy dynamic compaction. Suggestions of carrying on dynamic compaction in the cracking soil of anode zone were thus made for application in the engineering practice. Dynamic compaction should start when the water flow become smaller and the anode zone become dry.

Abstract：The current analysis on reinforced railway embankment does not take the confinement and friction effects provided by geocell into consideration. To deal with this issue，a new model considering the interaction between the ballast and the geocell was proposed on the base of large-scale direct shear tests. The typical results of embankment behavior from the numerical computation agreed well with those from the laboratory model tests，which confirmed the reliability of the analysis model established. Further systematical analysis on the influence of the ballast strength，geocell stiffness and foundation compressibility on the mechanical response of embankment were carried out. The results showed that the reinforcement made significant influence on the embankment behavior especially near the reinforced layer due to the confinement from geocell. And the effect was spread to the surroundings through the friction provided by geocell and gravel itself and was dissipated gradually. The weaker ballast and softer foundation soil were found to enhance the reinforcement effect on embankment behavior in a greater degree. In the case when the internal friction angle of ballast was 20°and the deformation modulus of foundation soil 5 MPa，the peak lateral displacement was reduced 60% and 72% respectively. The peak stress decreased as well and the distribution range increased markedly due to the reinforcement. The mechanical response of embankment was found to be sensitive to the elastic modulus of geocell in the ranges of 0.2 GPa to 2.5 GPa.

为研究夯锤对地基的冲击机制，探索表征夯锤冲击效能的方法，在黄土地基上开展392 N×2.5 m以及700 N× 1.4 m两组相同能级的强夯模型试验，以模型夯锤为研究对象，得到2组夯锤冲击黄土地基时的加速度时程曲线，并通过数值积分获得速度曲线及冲击行程的位移时程曲线。通过对比后发现，在相同击数下，低落距重锤的加速度峰值虽均比高落距轻锤的小，但重锤的冲击力峰值增加幅度却比轻锤的大；将夯锤冲击行程分为无效行程、夯沉量及地基反弹3个部分，定义夯沉量与夯锤冲击行程的位移计算值之比为夯沉比，得到夯沉比曲线及其表达式，从而用夯沉比来表征夯锤冲击效能。同时认为还可以根据一定标准，利用夯沉比及其曲线确定最优强夯击数，从而为优化强夯设计提供参考。

Through the force analysis of the group pile foundation，a vertical resistance coefficient of soil on the pile cap was proposed to calculate the uplift resistance and the stiffness coefficients of the pile top with the horizontal resistance were deduced based on the‘m’method. The deflection of the pile cap was calculated according to the force equilibrium equations and the internal forces and deflections of single piles were obtained with the deflection of the pile cap. Thus a method for calculating the single piles? internal forces and deflections of the group pile foundation was obtained. Finally，the single piles? internal forces and deflections of a group pile foundation with four piles were calculated under the uplift and compression conditions and the results were analyzed.