In order to explore the strength characteristics of stratified composite rock，a homogenization procedure was undertaken to convert the layered composite rock into an equivalent homogeneous one and an failure criterion based on the MLC failure criterion under true triaxial condition was established in terms of the strength and geometric parameters. A large number of tests on sandstone，siltstone，slate and composite rock under different true triaxial conditions(changing lode?s angle and ?3- and coefficient of intermediate principal stress-constant tests) were carried out with the multi-functional experiment system built in-house for fluid-solid coupling under true triaxial condition to investigate the effect of coefficient of intermediate principal stress on strengths. The results showed that the proposed criterion for layered composite rock described with fair accuracy the ultimate behaviour of layered rocks subjected to the true triaxial conditions.

The prominent issues in tunnel design and safety control，especially the design of tunnel in complex surrounding rock are highlighted based on the analysis of existing classification methods of rock. The existing methods of rock classification are unsuitable for the complex rock conditions and strict requirements of environmental control. Moreover，they provide little guidance for tunneling in complex conditions. In this paper，the concept of safety of surrounding rock and support system of tunnel is proposed based on the surrounding rock control. The safety of tunnelling in complex surrounding rock with limited self-stability is studied. The safety evaluation model of surrounding rock is proposed. The importance of ground pre-reinforcement in weak ground tunneling is illustrated and the analysis method considering the effects of ground pre-reinforcement is proposed. The relationship between the scale of surrounding rock and its response is established based on the analysis of the scale effect and the structure effect(time effect) of surrounding rock. Meanwhile，the factors that affect the tunnelling stability are analyzed in the mesoscopic level. The safety evaluation system of surrounding rock under complex geological conditions is established based on the analysis of the relationship between surrounding rock and tunnel support. The deformation ahead of tunnel face，the failure zone ahead of tunnel face and the effectiveness of ground reinforcement are taken as the key parameters to classify the tunnel safety in complex conditions. An evaluation system of tunnel safety composed of nine indices is therefore put forward. A project is also given to introduce the use of the proposed classification method of tunnel safety.

In this paper，an iterative method was proposed to calculate the air leakage rates and the stresses and displacements of the surrounding rock of lined rock caverns(LRCs) for the compressed air energy storage(CAES). The proposed method is based on the simplified solution for temperature and pressure variations in CAES caverns，the diffusion equation of polymers，the equation of radial laminar flow in porous media，and the analytical solutions for a circular hole in an infinite elastic medium. Five case studies were used to confirm the capability of the proposed method in correctly estimating the air leakage rates and the stresses and displacements of the surrounding rock. The proposed method is easy to be programmed and yields the results faster than the numerical modeling. Thus，the proposed method can be used in a primary study stage of CAES research(i.e.，sites selection，initial designing stage) or be compared with the results from the detailed numerical modeling to provide the critical information for further studies.

The seismic damage and seismic performance in underground engineering is a hot spot of research home and abroad. Due to the constraints of surrounding rock and soil，there is a big difference in the dynamic characteristics between the underground structures and ground constructions under earthquake. Because of the special deformation characteristics of underground structures，a lot of research have been carried out on theoretical and experimental study of seismic response. Furthermore，the damage characteristics and failure mechanism of underground structures have been analyzed，the current achievements of seismic performance evaluation of underground structures have been summarized，and important issues have been pointed out. The life cycle seismic response and performance evaluation indexes of underground engineering should be emphasized，especially the life cycle damage mechanism and the seismic performance design of underground engineering constructed in the strong earthquake zone.

This study investigated the compatible deformation model and the stability of the system of super-thick strata and coal pillars based on the recoverability safety of a longwall panel with large coal pillars under super-thick strata in Gaozhuang mine in Jining，Shandong province，China. The coal pillar was found to be able to isolate the gob and support the super thick strata and the overburden structure. The compatible deformation model for super-thick strata and coal pillars was established on the basis of the flexural deflection of super-thick strata and the vertical compressive deformation of coal pillars. The stress source，form as well as the entire compatible deformation mechanism of the vertical deformation of coal pillars were analyzed. The stress-strain relation of the compatible deformation for the system was deduced. The mode and criterion of system instability and its impact on dynamic disasters under mines were discussed. The disaster prevention and control techniques were proposed. The research results were applied to analyze the system stability of 3up1102 Longwall Panel before mining，and the disasters were forecasted. The rationality of the research was initially verified according to the micro-seismic monitoring results and the dynamic stress conditions at the recoverability stage. The purpose of quake without disasters has achieved through implementing the targeted preventive measures.

The fatigue damage theory has been proven to be practical in estimating the damage of rock subjected to the repeated action of freezing and thawing. The application of the established frost fatigue model in the calculation of rock damage in the natural environments still faces several challenges，for instance，how to simplify the complicated natural freezing and thawing action，how to define the damage variable reasonably and how to calculate the frost damage of rock caused by the joint action of multiple mechanisms. In this paper，analysis is carried out corresponding to the above challenges. The results indicate that the diurnal and annual freeze-thaw cycle should be the research focus in the engineering activities，which could be classified into the low-cycle or high-cycle fatigue loads according to the saturation degree of rock and the flow rate of unfrozen water in rock respectively. The change of the porosity of rock reflects the underlying frost mechanism，and the damage variables are thus defined by the flaw area and residual strain. The damage generated by high-cycle loads is comparable to that generated by low-cycle loads according to the fatigue damage model. Moreover，the effect of the action sequence of low-cycle and high-cycle loads should be taken into account.

为了进一步完善煤与瓦斯突出机制，通过对已有研究成果和煤与瓦斯突出地质结构环境的总结分析，将煤与瓦斯突出机制研究与工程结构相结合，提出煤与瓦斯突出的关键结构体模型，并对煤与瓦斯突出过程进行剖析，通过理论分析建立煤与瓦斯突出启动的力学判据Cm和能量判据Ce，形成煤与瓦斯突出关键结构体致灾理论。研究结果表明：地质构造运动形成构造煤体，营造利于突出发生的高应力环境，提供利于瓦斯保存和突出启动的地质结构环境；突出煤体具备高能瓦斯和构造煤的介质属性，是煤与瓦斯突出的基本条件，也是突出过程中能量的主要来源，关键结构体是煤与瓦斯突出得以成功启动的必要条件；依据关键结构体模型，煤与瓦斯突出分为准静载作用下的延迟突出(D-QSL)和动载作用下的瞬时突出(I-DL)2种类型；煤与瓦斯突出过程经历准备、启动、发展和终止4个阶段，突出准备阶段始于地质构造运动对煤体的改造，突出激发表现为结构2的突变失稳，隶属于突出准备阶段，突出能否成功启动决定于结构1的力–能条件；利用关键结构体模型和突出启动的力–能判据能够揭示典型煤与瓦斯突出事故的启动机制，可为煤与瓦斯突出预测与防治提供指导。

To identify the difference of current geostress distribution and stress accumulation in surface layer and shallow surface layer of Bohai strait and surrounding area，the data of 5 shallow hydraulic fracturing drills along the axis of the channel and the other deep drilling data in surround area were collected. The dispersed point charts of stress varying with depth were established and the regression formulas of each parameter with depth were calculated. The research shows that  ， change with depth linearly and  ， ， change with depth hyperbolically.  ， ，  change with depth almost linearly. The comparison of the regression formulae of surface and shallow layer show that the difference of regression formula of horizontal principal stress is significant，the difference of regression formula of lateral pressure coefficient is small and the difference of regression formula of ratio parameters is basically the same. These indicate that the surface stress data can be applied to the analysis of stress accumulation and seismic activity in the brittle crust. The combination of   with   is necessary to determine the energy accumulation at the points of   in stress accumulation analysis. The comprehensive research on   and   lead to the conclusion that 19 surface points in Bohai strait and 86% shallow points in the surrounding district are in the middle-low level of stress accumulation，and the crustal stability is high. Some points in Beijing，Tianjing and Tangshan are in the state of high stress accumulation，and the crustal stability is low which need more attention. But these have little impact to the cross-sea corridor.

The confidence interval of geotechnical parameters calculated by the t-distribution method is too wide under the small sample condition which leads to the conservative engineering design. The simulation on the random sampling survey for small samples was therefore conducted based on the population of c，φ which reflect the inherent variability of soil. The interval and point estimation results were obtained using the Bootstrap method to reconstruct the datum. The differences of the parameter estimation from the t-distribution method and Bootstrap method were compared. The discrete characteristics of safety factors of slope stability were analyzed based on the parameter estimation space built by the sufficient number of repeated sampling. For the same confidence level，the Bootstrap method sufficiently takes advantage of the empirical distribution information of small samples and effectively narrow the mean confidence interval of c，φ，and their lower limit values with guarantee rate are closer to the true values compared to t-distribution method. The two methods yield the same results of mean and variance of point estimation，namely their reliability indexes of slope stability are equal，but the means of safety factors of slope stability calculated by the lower limit value with guarantee rate using the Bootstrap method are relatively large，the discreteness of safety factors decrease. The improvement becomes more obvious with the increase of the variance level of parameters. On the condition of the same reliability，the Bootstrap method can reasonably compensate the safety risk of slope caused by the statistical uncertainty from small samples.

The mechanical properties of raw coal specimens containing gas from the B10 seam of －780 m elevation in Huainan coal mine were studied under the conventional high stress triaxial compression by using the modified adsorption-penetration-mechanical coupling test system. The deviatoric stress-axial strain curves of the raw coal containing gas have the stages of elastic deformation，yielding，post-peak brittle failure or strain softening. The elastic period shows the fluctuation associated with strain-softening and strain-hardening. The post peak brittle failure feature is apparent. Under the same initial gas pressure，with the increase of the initial effective confining pressure，the trend of transition between the brittle and ductile is weak. Increasing the initial gas pressure can result in more significant brittle failure if the initial effective confining pressure is kept constant. The deviatoric stress-lateral strain curve has the linear elastic stage which is very smooth. The deviatoric stress-volume strain curve of raw coal containing gas shows dilation under the low effective confining pressure in the pre-peak region. With the increase of the effective confining pressure，the volume dilation delayed. The peak strength increases linearly with increase in confining pressure or gas pressure. The common failure mode for the coal specimens is shear failure and the cohesion and friction angle are 14.02 MPa and 25.93º，respectively.

A rapid and accurate microseismic(MS) source location method is the foundation of MS monitoring to play a better forecasting and early-warning role for rock mass stability. The accurate travel time calculation of first arrival wave is the key to improve the location accuracy of MS source. Aiming at rock mass with complex velocities in actual engineering，like voids filled with air and partitioned velocities，the multi-stencils fast marching methods(MSFM) was introduced to calculate the travel time of first arrival wave，which is fast and with high precision and strong applicability for complex model. In this method，a new calculation stencil is generated by means of coordinate rotation to make the diagonal adjacent points of the mesh calculated，and the precision of the fast marching method(FMM) is improved in diagonal direction. Firstly，the accuracy and efficiency of the first or second order FMM and MSFM were compared and analyzed，showing that the second order MSFM has higher accuracy. Secondly，for rock mass with partitioned velocities model and one with a void，both single velocity model and the second order MSFM were used to calculate the travel time. Through comparing them to analytical solution，the average absolute errors of the second order MSFM were reduced by 97.65% and 95.18% compared with the single velocity model. Then，the rock mass model with partitioned velocities model and tunnels was built，and it was proved that the second order MSFM has strong applicability for complex model. Finally，the MSFM-based MS source location algorithm of rock mass with complex velocities was proposed，and applied to Baihetan hydropower station left bank slope of MS location. By trial location of four blasting events collected in fields，the relative optimal layer velocities combination was obtained，which had the minimum mean value(9.6 m) of location errors and was used to establish the void-considered velocity model. The reliability of this velocity model was validated by the travel time forward calculation of a blasting event. The 128 MS events in May 2015 were located by both the single velocity model and the proposed location algorithm，by comparing the location results，the located events by the latter were distributed as belts more obviously near the main damage zone(LS331 and LS337) than those by the former. The study concludes that the MSFM has very valuable application as a travel time calculation method，the proposed MSFM-based MS source location method can improve the source location precision effectively.

The accurate conformal function determines the accuracy of stress-displacement solution for the surrounding rock of roadways with the cross section of complex shape. The genetic optimization and sequential quadratic programming algorithm are thus applied to achieve the high-precision mapping for complex shapes of the cross section. The optimization scheme overcomes the low robustness and the sensitivity of initial value existed in the previous optimization algorithms and constrains the average relative error below 0.5% when the number of mapping coefficient is greater than 14. The elastic stress solution based on the complex function methods was derived，and utilized to systematically analyze the mechanical behaviors of the surrounding rock of three-centered arch. The tangential stress curve exhibits the double peaks of unequal heights under one-way vertical load，which correspond to the small arch and right-angle area with the stress concentration factors of 1.5–3.0 and 3.5–8.0 respectively. The stress concentration factors for side wall and floor are around 2 and －1 respectively. The stress concentration factors for large arch area are －1.0–1.5. The stress distribution of surrounding rock shows that the scope of influence for right-angle area is the largest，followed by the arch area，the side wall area and the floor area. Both the stress concentration factor and lateral pressure coefficient have the strict linear relationship with the slope   to be the growth rate of stress concentration factor. The tangential stress distribution on the boundary of roadway under different   can be known through the distribution of  .

In order to understand the failure and bearing characteristics of pillars，the compressive tests on the single pillar and double-pillar specimens were conducted. The deformation，load and acoustic emission information of pillars were recorded and analyzed. It was found that when a single pillar was compressed，its bearing capacity decreased gradually with the propagation of micro-cracks. When it was not strong enough to bear the external load，the elastic energy stored in the test machine would release rapidly and caused the pillar to fail abruptly. In the compression process of the double-pillar specimen with two pillars having the same mechanical property，two pillars bore almost the same load and deformed simultaneously. In the compression process of the double-pillar specimen with two pillars having different mechanical properties，the pillar with the lower strength degraded earlier and lost the bearing capacity firstly. The load was then transferred to the other pillar. The system lost the bearing capacity when the macro-slip appeared in the pillar with the higher strength. For the multi-pillar systems，the strength of individual pillar，the inner stress state and the external load circumstance all have the influence on the final stability. In the underground mining practice，in order to prevent the massive pillar collapse effectively，it is wise and necessary to leave the barrier pillars among the normal pillars.

Coal and gas outburst is a very complex dynamic disaster in underground coal mining process. In this paper，a numerical model was established based on the theory of particle flow to simulate the development of micro-cracks，displacement，force and velocity fields，and to investigate the microscopic mechanism of gas pressure and layer-stiffness ratio. The simulation results show that the coal and gas outburst is a relatively quick process. The shear cracks were mainly concentrated in the front tip of outburst，the tensile cracks occurred deep inside the coal. The gas outburst has great influence on the coal and rock damage. When the gas pressure is relatively small，the shear cracks occur at the front and the tensile crack reached deeper. When the gas pressure is relatively large，the shear cracks and tensile cracks penetrate into the same depth. The damage of coal and rock and the shear crack ratio increases. When the layer-stiffness ratios is not the same，the speed and shape of crack propagation are not the same.

The mechanical properties and deformation behavior of soil-rock mixture and underground structure in soil-rock mixture stratum are influenced by the particle size distribution. The mesoscopic structural characteristics of soil-rock mixture were analyzed based on the fractal geometry theory and the relationship between the quality-particle size grading curve and the fractal dimension was determined. The fractal analysis on grain-size of 34 groups of sand-gravel soil in coordinate system   was conducted and the results indicated that the sand-gravel in Beijing has the characteristics of self-similarity. The range of the fractal dimension of sand-gravel in Beijing is 2.4–2.6. The variation of the quality-particle size grading curve with the fractal dimension and maximum grain size were analyzed，yielding some new findings regarding the mechanical behavior of soil-rock mixture. It is clear that the whole grading curve can be obtained by combining the fractal geometry theory and the laboratory test on grain size distribution. A program generating the model of sand-gravel stratum is compiled based on the Monte Carlo method using the sphere to represent the shape of stone. Then，3D numerical analysis on tunnel excavation were carried out.

The problem of tunnel supporting in the expansive loess was investigated in this paper. A mechanical model for composite supports was established employing the theory of elastic shells. An improved procedure for computing the characteristic curve of ground supporting for tunnel in expansive loess was presented with the equivalent section approach and an expansive force variable. The study on the mechanical behavior of primary supports in loess tunnel was performed based on the proposed model and method. And then a suitable composite supports of steel，gird and shotcrete for the expansive loess tunnel was proposed. The model and method established were proved appropriate for the mechanical characteristic analysis of primary supports for tunnels in expansive loess，and it explained the failure of original primary support theoretically. The composite support allows the different materials to fully display its potentials to ensure the stability of tunnel and therefore have an advantage over the support methods of steel-shotcrete and grid-shotcrete.

A type of anti-swelling grouting material has been manufactured in order to meet the demand for the grouting reinforcement of the underground roadway in swelling soft rock. The main parameters of performance of the grouting material，such as the density，the bleeding ration，the setting time，the fluidity and the consolidating strength were studied in the laboratory tests. Meanwhile the reinforcement performance of the grouting material was researched in an in-suit experiment. The results show that the main parameters of performance of the grouting material are optimal when the water-cement ratio is 0.5：1 and the ratio of the additive is 5‰. The grouting material is confirmed to improve effectively the property of the surrounding rock and enhance the strength of the broken and swelling soft rock. Meanwhile the grouting material also prevents the swelling deformations of the soft surrounding rock during the grouting process.

To study the mechanical properties of structured soils under undrained conditions，the triaxial compression tests on reconstituted soils and two kinds of structured soils with initial stress-induced anisotropy and isotropy were carried out under axially loading-unloading-reloading. The soils were tested under consolidation- undrained(CU) conditions at the confining pressures of 25，50，100，200 and 400 kPa，and the results of tests are analyzed with the binary-medium theory. It is found that the structured soils have stronger structures at lower consolidation stress. Meanwhile，Eave does not change significantly in different stress cycles. When the confining pressures are higher，the structures of soils are weakened，and their characteristics are similar to those of reconstituted soils. Because of the structure weakening and positive pore pressure，Eave decreases with the increase of εa. With the increase of the axial strain，the breakage rate of the bonded components and the soil particle spacing of friction components increase. In the meantime，the tendency of the volume contraction becomes more apparent when unloading.

A set of test system for studying the vertical infiltration in one-dimensional soil column under rainfall was developed. Four sets of tests were carried out to the unsaturated disturbed loess column under the different rainfall intensities. The time curves of the infiltration rate，the depth of the wetting front and the volumetric water content at the monitoring points were obtained.The formula of permeability coefficient was derived and the curve of the permeability coefficient varied with the matric suction of the disturbed loess was obtained. The rainfall intensity has great impact on the vertical infiltration in soil column. The infiltration rate equals to the rainfall intensity when the rainfall intensity is less than the minimum infiltration capacity of soil column. When the rainfall intensity is greater than the minimum infiltration capacity，the curve of infiltration rate can be divided into three stages，the non-compressive infiltration，the compressive infiltration and the saturated infiltration. The moment of occurrence of the dropsy point and the saturation point are different under different rainfall intensities，the greater the rainfall intensity，the earlier the dropsy point and saturation point appear，and the longer the stage of compressive infiltration. The permeability coefficient of the unsaturated remolded loess decreases exponentially with the increasing of matric suction.

A series of experiments on frost heaving of 1D saturated silt columns were conducted under the different experimental conditions to comprehensively investigate the influence of temperature gradients，freezing rate，height of sample and vertical load on frost heaving. The temperature of samples，the vertical load，and the amount of frost heaving and the water intake were measured during each experiment. The experimental results show that when the temperature is quasi-steady，the frost heaving rate increases proportionally with the temperature gradient and decreases linearly with the vertical load. The specific freezing rate was defined as the ratio of freezing rate to the height of sample. When the temperature is unsteady，the frost heaving rate increases with the specific freezing rate in the form of power law and the rate of increasing decreases as the specific freezing rate increases. A formula for calculating the frost heaving was presented upon the comprehensively consideration of the temperature gradient，freezing rate，vertical load and height of sample. The thermal diffusion equation considering the water migration in frozen soil was deduced on the basis of the formula of frost heaving and the numerically solution was presented. The numerical results of the variation of temperature and frost heaving were compared with the experimental data，which confirmed the reliability of the simulating method.

The interaction between the surrounding soil and pile with variable cross-section is represented by a Voigt model and the spring constant and damper coefficient is derived. Thus a more rigid pile-soil interaction model considering the interaction of variable pile section and surrounding soil is proposed. An amended impedance function transfer method is proposed by taking Laplace transforms on the continuity conditions of displacement and stress. The surrounding soil layers are modeled as a three-dimensional axisymmetric continuum and the pile is assumed to be a Rayleigh-Love rod with material damping to study the transverse inertial effect of the pile of large diameter. The impedance function at pile top is derived with the amended impedance function transfer method proposed in this paper. Then the velocity response at pile top is obtained. The solutions with and without the interaction of variable pile section with surrounding soil are compared. Meanwhile the coupling between the related parameters and the interaction of variable pile section with surrounding soil are analyzed.

The dredger filling has the characteristics of large void ratio，high water content and high compressibility. The permeability，compressibility and drainage path change greatly during the consolidation and the soil layer below the sand drains consolidates also under the effect of sand drains and the vacuum preloading. The governing consolidation equations under the Eulerian coordinate system were deduced based on the large strain consolidation theory，which considered both the large strain of soil and the partially penetrated vertical drains. A FDM program was compiled to solve the governing equations deduced. The shallow improvement of the ground of a project was analyzed. The calculated result agrees well with the field data.

Piezocone penetration test(CPTU) has advantages in directly providing the most original soil parameters and reflecting in detail the nonlinear variation of deformation with depth. The relationships between the parameters of piezocone profiles and the parameters of p-y curve were established and the p-y curve method using the CPTU data for determining the horizontal bearing capacity of single pile was proposed. The method was verified by comparison with the in-situ pile data from Jingjiang，Suqian and Kunshan sites. Results indicate that the p-y curve method based on CPTU can accurately reflect soil resistance development characteristics，which is a highly efficient and rapid method for determining the horizontal bearing capacity of pile foundation.