The engineering practices both in China and other countries indicate that the discontinuous surfaces existing in natural rock mass have strong effects on the stability conditions of geotechnical structures and even a decisive influence. It is significant to reveal the underlying unsolved problems of seepage behaviors and mechanical mechanisms of jointed rock mass. Based on the review of a lot of research works in the problems of mechanical characteristics for fractured rock，the present work proposed the research focuses and development directions from the viewpoints of theoretical approaches，indoor test，in-situ test and numerical methods，and mainly discussed these topics as follows：field investigation techniques and generation methods of fracture network，stress-flow characteristics of fractured rock mass，macroscale and microscale progressive failure mechanisms of fractured rock mass, and anchoring techniques in underground engineering of fractured rock mass.

In order to investigate the long-term stability of rock engineering in different alpine environments，the pore structures of quartz sandstone，meta sandstone and red sandstone subjected to freeze-thaw cycles in three different temperature ranges were measured by the nuclear magnetic resonance(NMR) technique，and triaxial creep experiment was conducted on the sandstone after freeze-thaw cycles to study the creep characteristics in different temperature ranges. The results show that the action of freeze-thaw cycles promotes the development of mini-pores and meso-pores in the sandstone，and that the development degree of the pores in the red sandstone and the meta sandstone subjected to cycles is affected by the range of freeze-thaw temperature while the freeze-thaw damage degree of the quartz sandstone is barely related to the freeze-thaw temperature. The creep strain of the sandstone increases with the number of freeze-thaw cycles，while the long-term strength gradually decreases. The freeze-thaw temperature controls the rising amplitude of creep and the decreasing trend of the strength of the sandstone after cycles. Furthermore，the time-dependent mechanical response of the red sandstone to the temperature range is the most prominent，while the accelerated creep of the quartz sandstone and the meta sandstone under failure stress level is prone to occur after cycles in a larger temperature range. A new fractional-order damage creep model was proposed based on the theory of statistics damage and fractional calculus，and the constitutive equation of the model is further extended to a three-dimensional form to simulate the triaxial creep behaviour of the sandstone after freeze-thaw cycles. The bulk modulus and visco-elastic shear modulus of the fractional-order damage creep model generally decrease with the number of freeze-thaw cycles and the temperature range，and the value of the fractional order and the time-dependent damage parameter are related to the creep time and the deformation scale of the sandstone. The great accordance between the fractional-order damage creep model and the experimental data reveals that the model can accurately reflect the whole creep process of the sandstone after cycles in different temperature ranges.

In order to reveal the effect of dynamic loading frequency on fracture evolution characteristics of pre-flawed rocks，GCTS-RTR 2000 rock mechanics testing system，in-situ acoustic emission monitoring and post-test CT scanning were employed to carry out increasing-amplitude fatigue loading experiments on rock samples with an approaching angle of 50°. Testing results show that the strength，deformation and fatigue life increase with increasing the dynamic loading frequency. The growth rate of the volumetric strain shows a trend from steady increase to sudden increase，and at the final fatigue loading stage，the deformation increases sharply until the sample fails. AE count，AE energy change and crack propagation behavior are controlled by the dynamic loading frequency. The accumulative AE count and AE energy increase with increasing the loading frequency. The AE spectral frequency analysis reveals six kinds of crack types. The crack size is negatively correlated with the frequency and the proportion of the high frequency-high amplitude signal decreases with increasing the frequency, indicating that large-scaled cracks are prone to form under high loading frequency. CT images show that the scale of the crack network at the rock bridge segment increasing with increasing the loading frequency，and the coalescence of the pre-flaws easily occurs for rock subjected to low dynamic loading frequency conditions while is difficult under a high dynamic loading frequency. The testing results are helpful to improve the understanding of the influence of the dynamic frequency on the fatigue mechanical properties and the crack evolution behavior under increasing-amplitude fatigue loading and provide necessary theoretical basis for the monitoring and warning of structural deterioration，pattern recognition and long-term stability of rock mass under increasing-amplitude fatigue loading.

In the blasting process of underground rock mass，the geo-stresses and dynamic loads are different at different distances from the blasting source，which leads to different response characteristics of rocks. In order to study the influence of dynamic loads on the dynamic strength and deformation characteristics of rocks with different geo-stresses，a modified SHPB test device was used to carry out three-dimensional dynamic compression test on red sandstone by setting five impact velocities and five axial static stress levels respectively to simulate different dynamic loads and geo-stresses. The variation rules of average strain rate，dynamic peak stress(or dynamic compressive strength)，ultimate strain and dynamic deformation modulus of red sandstone under different impact velocities and static stress conditions were analyzed respectively，and the evolution empirical models of dynamic response parameters of red sandstone were built to characterize the dynamic response characteristics of rocks. The results show that：(1) the strain rate of red sandstone is affected by the impact velocity and the static stress，and the average strain rate decreases first and then increases with increasing the axial static stress and increases as a power function with the impact velocity，(2) under the same three-dimensional static load，the peak stress and ultimate strain of red sandstone increase by a power function with the impact velocity，(3) under the same impact velocity，with increasing the axial static stress，the peak stress of red sandstone increases as a power function and the ultimate strain also gradually increases，and (4) with increasing the axial static stress，the critical impact velocity and dynamic compression strength of red sandstone both increase first and then decrease. The research results are beneficial to the perfection of rock dynamics theory and the prediction of the response characteristics and stability of surrounding rock mass according to the type and amount of explosives in engineering blasting.

Discontinuous structural planes have great influence on the propagation of explosion stress waves in rock mass，and studies on the dynamic collapse mechanism of rock mass with large structural planes under stress waves provide a theoretical basis for mining and stability control of rock mass under geological structure conditions. Based on the collapse of adjacent 56–#7 pillar stope induced by stoping in 56–#8 room stope of Dongguashan Copper Mine，a mechanical model of shear slip instability of structural planes is established. Based on Mohr-Coulomb strength criterion，the transmission and reflection coefficients of explosion stress waves passing through a structural plane are calculated by theoretical analysis method，and the stress response characteristics of stress waves passing through a structural plane are analyzed. The energy criterion and the stress criterion of shear slip are derived，and the condition of shear instability is obtained. By weakening the shear strength parameters of structural planes，the damage law of structural planes caused by millisecond blasting is analyzed. As is shown by the research findings：(1) when the incident angle is in a certain range，the reflected wave does not have phase delay，the energy dissipation coefficient is greater than 0，and the structural plane shear slip occurs，(2) the shear slip instability of the structural plane is related to the shear strength parameters(internal friction angle and cohesion)，the incident angle of stress waves and the distance between the blasting source and the structural plane，and the farther the blasting source is from the structural plane，the larger the shear strength parameters of the structural plane and the less prone to shear slip instability，and (3) when the parameters of the structural plane reach the critical condition of shear slip，the stope of 56–#7 pillar collapses.

The biotite quartz schist is a typical anisotropic rock caused by mineral arrangement. In order to study its damage evolution law and anisotropic characteristics，the equal plastic strain cyclic loading and unloading tests with acoustic-force joint measurement were carried out on the samples with schistosity angles of 0°，45° and 90°. The results show that，with increasing the plastic strain，the variation trends of the initiation strength ，the damage strength  and the peak strength  of three kinds of samples are similar，and the plastic strains corresponding to stable  and  are same. For the 45°samples with strong control effects by schistosity，the confining pressure has little influence on the evolution of the strength characteristic value ratio，and the damage can fastly reach a stable state with growing the plastic strain. During the evolution of the shear strength parameters，the variation rate of the shear strength parameters of the group samples with a schistosity angle of 45° is the largest based on the critical plastic strain of the cohesive and the friction angle，followed by 0° and 90°， showing that the cohesion rapidly losses while the friction angle rapidly increases when the effect of schistosity control is strong. The corresponding plastic strain of the integrity coefficient evolving to a stable state is the same as that of . However，the different schistosity angles have different effects on acoustic transmission，resulting in the differential evolution of the integrity coefficient under different confining pressures，especially for the samples with a schistosity angle of 90°. This study explores the special mechanical behaviors of the damage evolution of anisotropic rock caused by the directional arrangement of minerals according to the analysis of quantitative indexes.

When a tunnel crosses a fault fracture zone，in order to avoid the occurrence of water inrush，collapse and other disasters，the construction plan of pre-grouting and then blasting excavation is often used. It is of great significance to clarify the blasting damage characteristics of grouting rock mass for the safe construction of the tunnels through faulted fracture zones. This paper takes the construction of Longnan tunnel of Ganzhou-Shenzhen high speed railway through fault 8 as an example. The distribution law of acoustic wave velocity with depth in the surrounding rock after tunnel blasting was obtained using the two-hole acoustic method test. Based on the stress criterion and the elastoplastic constitutive model，a statistical damage model of the rock mass was established，and a new LS-DYNA solver was generated by Fortran compilation. The cumulative damage evolution and distribution law of grouting reinforced surrounding rock of the tunnel under the effect of 10 cycles of blasting excavation was calculated by using the complete restart algorithm，which basically matched with the field acoustic testing results. Numerical analysis results show that the maximum damage depth of the surrounding rock is located at the bottom of the inverted arch after blasting，and the average damage depth does not exceed 2.5 m at the vault，the shoulder and the waist of the arch，which need anchor anchoring. The degree of damage to the surrounding rock in the arch foot of the upper and middle steps of the tunnel is the most serious，but the depth of damage to the surrounding rock is small. However，the degree of damage to the surrounding rock in other key areas besides the arch foot is small but the depth of damage is large.

In this paper，a rock tunnel model with a spandrel crack(RTMSC) was proposed，and the initiation and propagation rule of mixed mode I/II cracks under blast loading were studied. Crack propagation gauge and strain gauge were used in the experiment to monitor crack initiation，propagation and arrest. AUTODYN code was used for numerical simulation，and ABAQUS code was used to calculate the dynamic stress intensity factors and(SIFs). The results show that：(1) in the process of crack propagation，there are crack arrest points on the propagation paths in which crack propagation time is relatively long，(2) bore locations affect crack initiation，arrest and propagation significantly，(3) in the process of crack propagation，the dynamic energy release rate is not a constant，and (4) with increasing the crack propagation speed，critical SIFs of both mode I and mode II decrease gradually.

In order to better apply the numerical methods to the slope stability calculation，a 3D slope stability control analysis method based on the column grid discretization of stress fields is proposed. After the numerical calculation of a three-dimensional slope is completed，the minimum cube surrounded by the length，width and height of the three-dimensional slope is divided into m×n×k cube grids，then those cube grids at the same plane position are connected in series along the height direction to form m×n column grids. In this way，a three-dimensional coordinate system is constructed，which includes both the three-dimensional grid of slope columns and the grid of numerical calculation units. Firstly，by searching the numerical element corresponding to the center point of any i cubic grid，the numerical stress field is discretized into grids. Secondly，the expression of the safety factor based on the shear stress in the sliding direction of the sliding surface is proposed，the solution method of the vector of the sliding direction of any sliding surface in the column grid is derived，and the calculation model of the minimum safety factor in the grid is established. Thirdly，the search condition and search mode of the slip surface based on the combined control of the safety factor and the deformation are proposed，and the 3D slope spatial slip surface is obtained by searching the potential slip grid that best meets the control condition. Finally，the feasibility，rationality and superiority of this method are verified by typical examples，the influence of the spatial effect on the safety factor and the deformation of a three-dimensional slope is analyzed，and a correlation curve between the safety factor and the displacement under controllable conditions is proposed. The research results have important scientific significance and application value for the numerical calculation of 3D slope stability and safety control under complex conditions.

In order to investigate the macroscopic and mesoscopic mechanical properties of cemented waste rock backfill using fractal gangue，the ultrasonic detection，uniaxial compression and microscopic scanning tests were carried out on cemented waste rock backfill of which the aggregate size distribution satisfies fractal theory. The ultrasonic，strength，deformation and microstructure characteristics of cemented waste rock backfill were studied. A particle flow model considering the aggregate size distribution，multiple particle media and contact boundaries was constructed for simulating cemented waste rock backfill. The evolution laws of the energy，crack，force chain and particle failure of cemented waste rock backfill during the whole loading process were explored. The influencing mechanism of the aggregate size distribution on the mechanical property of cemented waste rock backfill was revealed from the microscopic and mesoscopic views. The results show that the ultrasonic pulse velocity and the compressive strength of cemented waste rock backfill have a quadratic polynomial relationship with the fractal dimension of the aggregate size distribution，while the peak strain is negatively correlated with the fractal dimension. The fractal dimension of the optimal aggregate size distribution for cemented waste rock backfill is between 2.4–2.6，which shows a more uniform microstructure. The peak strain energy of cemented waste rock backfill increases firstly and then decreases with the fractal dimension of the aggregate size distribution，but the low fractal dimension of the aggregate size distribution is more conducive to strengthening the friction effect in the structure. The cracks initiate from the stress concentration of the sharp corners of aggregates in cemented waste rock backfill，develop along the cementing-aggregate boundaries，and propagate along the weakest or thinnest cemented matrix to the adjacent sharp corners of aggregates or fracture interfaces in the cemented matrix. The fractures of local force chains are prone to occur in the cemented waste rock backfill with a low fractal dimension of the aggregate size distribution，showing obvious early local crack accumulation and particle bulking. The increase of the fractal dimension of the aggregate size distribution can weaken this local failure characteristic，but the increase of the fine aggregate proportion causes the expansion of the interfacial transition zone，which induces more force chain fractures of cementing-aggregate boundaries.

The earthquake investigation and the engineering practice both show that it is necessary to develop reasonable liquefaction prediction methods in deep buried sand layers under the actions containing severe seismic ground motion for modern cities and major projects. Based on the survey on the recent liquefaction events and the analysis for the existing representative liquefaction prediction methods，a SPT-based unified discriminant model and the corresponding formula are proposed suitable for sand layers of different buried depths under the action containing the severe seismic ground motion. The proposed hyperbolic model has a consistent and unified expression for sand layers of different depths and conforms to the basic characteristics of the liquefaction critical line. The proposed model can adapt to the situations of shallow and deep sand layers as well as high and low seismic intensities and hence，is more reasonable than the existing models in China's codes and more advanced than the international CSR theory-based NCEER models with four sections along the depth. The new formula is approved by a large number of measured liquefaction data within sand layers of 30 m buried depth under PGA＜0.9 g，which overcomes the serious conservative disadvantages in the buried depth range of 10–20 m in China's codes and makes up for the vacancy of the discriminant methods for PGA＞0.4 g and the sand layers below 20 m in China's codes. The new formula also eliminates the unreasonable phenomenon of NCEER method that the critical boundary of liquefaction turns back when the buried depth of sand layers exceeds 10 m and overcomes the relatively conservative shortage of NCEER method under very strong and severe ground motion of 0.25 g＜PGA＜0.9 g. The proposed formula has been adopted in the revised version of the General Rule for Performance-based Seismic Design of Buildings with role model and can provide guidance and technical support for related specification revision and engineering application.

To study of the dynamic responses of sand under cyclic loading in the geotechnical engineering，including liquefaction，deformation accumulation and stiffness degradation，a constitutive model for simulating the effect of cyclic loading is first developed by introducing a shear strain reversal technology into the simple critical state sand model(SIMSAND). Then，the degradation of the strength during the simple shearing process is realized by incorporating the structural anisotropy of the granular material. Furthermore，the proposed cyclic model is verified by the triaxial cycle test and the simple shear cycle test on Fontainebleau sand. The enhanced model is implemented into finite element code ABAQUS for explicit dynamics analysis. Using the cyclic model pile test carried out by the French National Road and Bridge Laboratory(ENPC)，finite element simulations are performed to study the dynamic response of piles under long-term cyclic loading. The results show that the enhanced cyclic SIMSAND model can reasonably predict the behavior of cyclic densification and strength degradation of the sand under pile-soil interaction.

Based on summarizing the displacement-dependent earth pressure discipline and mathematical fitting methods，and adopting Sigmoid function to describe the relationship between the extrusion or relaxation stress and the displacement of a retaining wall，a new mathematical fitting method and its formula of the earth pressure were presented to account for the displacement of retaining walls. The initial condition and mathematic features of the proposed formula were checked，and the only remaining parameter was back-analyzed from the existing displacement-dependent earth pressure equations and available model test results. The proposed formula was further verified by model tests，numerical simulations and representative mathematical fitting equations reported in the literature. Finally，the Nash-Sutcliffe Efficiency criterion and the Percent Bias criterion were employed to quantitatively evaluate performance differences between the new method of this study and representative mathematical fitting equations. The results show that the proposed new mathematical fitting method and its formula，satisfying the initial conditions and increasing monotonically with an inflection point，have a broad prospect of engineering applications due to the fact that they are simple and practical，and the efficiency and percent bias are in an overall excellent level according to comprehensive validation against model tests，numerical simulations and representative mathematical fitting equations. This study can provide useful references for the sophisticated calculation of the earth pressure and the optimal design of retaining walls.

Evaluation of site liquefaction，according to which some remediation measures can be adopted to avoid liquefaction-induced damage，has important research value. Based on cyclic triaxial numerical tests，in this paper， a new energy-based pore pressure model for evaluating site liquefaction was proposed by taking the Arias intensity of seismic waves as the energy parameter，and the effects of the consolidation pressure and the consolidation ratio on the proposed model were discussed. The energy-based pore pressure model was verified by the cyclic triaxial tests results. Based on the verified model，a new method taking into consideration of the permeability and the shear stress reduction coefficient was proposed for evaluating the liquefaction. The new method was verified by centrifuge tests and numerical simulation. The results show that the new method can accurately predict the generation and accumulation of the excess pore pressure and hence，can be used to evaluate the liquefaction of ground.

The long-term water leakage of shield tunnels seriously affects the water and soil loads on the outside of the segments. Through theoretical analysis，the expression of the vertical average permeability gradient over the tunnel roof and the calculation formula of the lateral earth pressure coefficient considering the arching effect of maximum principal stress were obtained，and the calculation model of the water and soil load on the top of the tunnels considering the effect of long-term water leakage was further constructed. Relying on the geological conditions of two typical sections of the Hengqin tunnel，the theoretical analysis results were compared with the field measurement results of the water and soil load under different calculation conditions. The following conclusions are that the model in this paper can reasonably and effectively evaluate the water and soil pressure on the top of shield tunnels in marine and land sections and has the smallest error compared with the Dimitrios Kolymbas effective stress method and the Terzaghi total stress method. With increasing the friction angle，the lateral earth pressure coefficient shows a slight decrease first and then increase trend，indicating that the soil arching effect can play a leading role in the lateral earth pressure coefficient when certain conditions are reached. The water and soil load on the top of the tunnel presents a non-linear positive correlation with the buried depth ratio of the tunnel，a linear positive correlation with the soil gravity and the water head outside the segment，while a linear negative correlation with the leakage of a single width. Related research results can provide theoretical basis for the rational design of underwater shield tunnels.