In order to study the effects of non-coplanar overlapping flaw inclination on the axial stress，elastic strain energy and local stress field of rock-like specimens under uniaxial compression，numerical simulation adopting particle flow numerical analysis software PFC2D was carried out based on the actual parameters of existing rock-like samples. The results show that the compressive strength of the rock sample increases with increasing the dip angle of the flaws. When the dip angle of the flaw is small，the sample has obvious plastic deformation during uniaxial compression and the energy release rate is large in the strain softening stage. In the case of a large dip angle of  the flaw，the sample shows obvious elastic brittleness and large energy storage capacity. Analysis of the local stress field of the flaws indicates that the minimum principal stress field obviously changes with the axial strain. The large stress drop is related to the accelerating propagation of the cracks. The minimum principal stress filed can be classified into three different types according to the variation of the stress field. In the early stage of loading，the minimum principal stress of the upper and lower sides of the flaws is tension stress. With increasing the dip angle of the flaws，the stress concentration decreases，the tension zone is transferred to the tip of the flaws and the area is gradually reduced. The tensile stress gradually disappears after the flaw is cracked. Although the stress concentration near the tip of the flaw is high in the early stage of loading，the two-dimensional compressive stress state makes the crack initiation of the region relatively difficult.

To comprehensively research the characteristics of mesoscopic minerals and microscopic fractures of granite，the split Hopkinson bar(SHPB) device was employed to perform the spalling experiments of granite rods under different impact loads. The mesostructure of minerals was studied by crystal mineralogy，the meso-crack propagation was recorded by a high-speed camera，and the microstructure of the fracture surface of the samples was observed by energy dispersive spectrometer(EDS) and scanning electron microscopy(SEM). The roughness of the fracture was calculated quantitatively with the fractal principle. The experimental results show that the mesostructure of granite minerals has an important influence on the spallation failure，especially for feldspar，quartz and mica which are the main components of granite. The distribution of these minerals also affects the expansion of mesoscopic cracks. It is also demonstrated from the microscopic analysis of EDS and SEM images that different minerals present different micro-fracture characteristics and that the fragmentation degree and roughness of the fracture increase with increasing the impact load，which was greatly validated by the fractal dimension values.

In this study，a field engineering experiment was conducted in a fault-affected roadway of 9101 mining face in Xiashanmao coal mine，and the distribution laws of mine pressure and control techniques of the roadway surroundings were studied by numerical simulation and field monitoring. The results indicate that the entry retaining process shows obvious staged characteristics when crossing a fault. When the mining face is in the transition region of the hanging wall and footwall，the stability of the roadway and distribution laws of the mine pressure are quite different from those under a conventional geological condition. The abutment pressure of the mining face near the fault is appropriately 55.1% higher than that of the conventional geological condition. When the mining face crosses the fault，the abutment pressure experiences a sudden drop owing to the decrease of the stress transmission between the hanging wall and the footwall. In the fault-affected area，the average load of hydraulic supports，the pressure of the temporary support and the stabilized distance of the retained entry respectively increase appropriately 47%，20.5% and 13 m compared with those in the fault-unaffected area. To address the strong pressure and large deformation problems in fault-affected roadways，a “roof cutting and rib control support + door-type support + single prop” support strategy was proposed to control the roof deformation，a “W-type steel band and NPR cable” support strategy was used to control the coal rib deformation，and connective U-type steels were used to control the gangue rib deformation. Field test shows that，after using the new support system，the roof，coal rib and gangue rib deformations decrease by 74%，72% and 71%，respectively. The deformations of the entry surroundings were effectively controlled in the fault-affected area after using the new techniques.

The macroscopic mechanical properties of granite under thermal shock are closely related to the thermal shock velocity. Mechanical strength failure tests were conducted by using self-developed rock thermal shock cracking test bench，and the relationship between macroscopic mechanical parameters of granite and the thermal shock velocity under thermal shock was investigated. The results show that granite under thermal shock presents significant characteristics of unsteady heat transfer，and that the surface temperature，instantaneous thermal shock velocity and average thermal shock velocity present three distinct stages including rapid cooling for the first 20 s，slow cooling from 20–150 s and constant temperature after 150 s. At the first stage，the thermal shock velocity has a decisive effect on the macro mechanical parameters of granite and the thermal shock failure of granite is the most severe. The quantitative calculation formulas of compressive strength，tensile strength，cohesion，internal friction angle and thermal shock velocity were obtained，and a thermal shock factor representing thermal shock failure capability was proposed to further quantitatively classify thermal shock failure capability. The research work can enrich and develop the failure theory of high-temperature rock mechanics.

In order to investigate the fracture characteristics and water outburst risk of mining floors above confined aquifer，mechanical models of both stope floors and water-resisting key strata were constructed to theoretically calculate the longitudinal failure range and transverse water-inrush zone of the floor under periodic weighting，and the fracture characteristics and seepage trend of the mining floor above confined aquifer were revealed using finite difference hydro-mechanical coupling modeling method and similar simulation test. The theoretical calculation shows that after coal seam excavation，the failures of the floor along the strike and inclination of the working face present“spoon-shaped”and“inverted saddle-shaped”respectively，and that the maximum failure depth of the floor is located near the boundary between the mined-out area and the coal body，which is roughly similar to the simulating result. The water gushing positions of water-resisting key strata are theoretically located in the areas including the side of the working face，50 m behind the coal wall and both sides of the goaf. However，the risk of water inrush in the central part of the side area of the working face is the highest，which coincides with the experimental observations and the numerical phenomena. It is observed that the shear and vertical cracks well develop in the shallow floor near the mining face and starting cut while that the layered cracks appear in the rock mass below the goaf. The maximum damage depth obtained by the test is 12.8 m，slightly less than the theoretical calculation and numerical simulation results of 13 and 15.875 m. The research results of this paper reveal the water inrush location and risk of mining floor，which can provide a theoretical basis for mine water treatment.

Aiming at that the existing calculation model of anchored slide-resistant piles fails to fully consider the actual geological conditions，a calculation and analysis model of anchored slide-resistant piles under the condition of compound multilayer sliding bed was established based on the theory of deformation coordination. The tension forces of each row of cables can be solved by simultaneous equations，and then the distributions of the internal force and displacement of anti-slide piles are obtained. The control conditions of the calculation model were improved and the rationality of the improved calculation model was verified by the displacement of the pile top and the stress of the pile side. The computation program of the improvement method was written by MATLAB and two project cases were calculated by both improved and traditional algorithms. Comparisons between the calculation results of two cases by numerical simulation and practical monitoring data show that the improved algorithm is more accurate than the traditional algorithm and that both the deformation and the internal force of the pile calculated by the improved algorithm are smaller than those by the traditional algorithm. For two cases，to be specific，the displacements of the pile top decrease by 17.0% and 28.7% respectively and the maximum bending moments decrease by 10.64% and 20.90% respectively. It is indicated that the traditional method is conservative for design and hence results in a higher project cost. The proposed method can provide a theoretical basis and reference for the design of anchored slide-resistant piles in the area of composite multilayer rock mass.

The uniaxial impact compression tests of coal-rock-like combined body with pre-existing cracks are carried out by using split Hopkinson pressure bar(SHPB). The energy evolution characteristics with different pre-existing cracks are investigated，and the influence of the position and dip angle of cracks on the fractal dimension of the combined body is analyzed. The results show that the energy dissipation and fractal characteristics of the cracked combined body are affected by the dip angle and location of cracks. The energy dissipation ratio and the energy dissipation density of the combined body with cracks in coal body or joint surface are smaller than those in the intact combined body，while the combined body with cracks in rock does the opposite. The dip angle of 30° or 60° has a greater influence on the energy dissipation ratio and the energy dissipation density than 90°. The fractal dimensions of cracked combined bodies in the case of cracks locating at rock or the dip angle of cracks equal to 90° are close to those of intact combined bodies or a large difference occurs. It is suggested that the construction parameters should be arranged reasonably according to the strength of the combined body and the distribution of cracks to achieve a better effect during excavation and reinforcement.

Analysis and prediction of stress fields along the Sichuan—Tibet railway area is of important significance and high application value. Combining the tectonic stress field zoning，geomechanical trace analysis method and Anderson?s theory of faulting mechanics，the stress orientations along the new Sichuan-Tibet railway area were analyzed based on the databases from WSM and Crustal Stress Database of China Mainland. The strength of rock masses in the engineering area was estimated by using Hoek-Brown criterion，the stress magnitudes of this area were predicted by the modified Sheorey model，and consequently，the stress state and potential high stress were comprehensively evaluated. The results show that the regional dominant orientation of SH is NE while that the orientation of the stress field varies around the Namche Barwa Terrane，Eastern Himalayan Syntaxis and the northeastern margin of the Qinghai—Tibet Plateau. The dominant orientation of SH near Eastern Himalayan Syntaxis is NNW–NEE，and the range of the orientation is 20°–140° at the northeastern margin of the Qinghai—Tibet Plateau. The predicted results indicate that the maximum and minimum horizontal principal stresses at a burial depth of 1 000 m along the new Sichuan-Tibet railway are respectively up to 26.19–38.41 MPa and 13.88–21.81 MPa and，at a burial depth up to 2 500 m，are 66.44–86.48 and 35.02–49.11 MPa respectively. It is also pointed out that，under such high stress，brittle failure or rock bust of hard rock and large deformation of soft rock would occur in the case of the overburden over 1 000 m. According to an application case，the proposed method works well combined with the databases and limited stress measurement results.

Aiming at major seepage problems in deep geotechnical engineering，a seepage and erosion device with a maximum core length of 1 500 mm was independently developed to reveal the seepage mechanisms of various fluids in deep strata，and seepage tests of saturated brine and gas in cores(off-white sandstone) were carried out. A general mathematical model describing the relationship among seepage velocity，seepage range and pressure gradient was established. The results demonstrate that，under the same temperature(50 ℃) and stress(16 MPa) condition，the seepage velocity of gas is extremely fast and about one hundred times of that of brine. The seepage of brine and gas is in accordance with Darcy?s law，and the test results are in good agreement with the theoretical calculations with a correlation coefficient of 99.8%. The relationship between the seepage range of brine and gas with time can be described by a power function，showing rapid growth in the early stage and gradual stabilization in the later stage. However，the seepage range of gas displace brine has no direct relation with time，which can be approximated as the combination of brine and gas seepage. In addition，the permeability and porosity of crystallized samples after brine seepage are lower than those of uncrystallized samples，which means that salt crystals have a certain filling and plugging effect on rock voids. This study confirms the feasibility and practicability of the developed device and provides a research method and idea for medium seepage in deep strata，which is helpful to reveal new scientific problems and to solve practical engineering problems.

The support system of prestressed anchor cables can effectively reduce the expansion of the plastic zone of the surrounding rock in underground cavers. Based on in-situ monitoring and numerical analysis for the high-wall and long-span underground caverns，the deformation evolution process of the surrounding rock and the time-dependent characteristics of the anchor cable tension are analyzed. Three types of change modes of the anchor cable tension，including monotonically increasing，decreasing firstly and then increasing，and monotonically decreasing respectively at the top arch，arch waist and side wall of the underground cavern，are proposed. The deformation characteristics of the anchored rock during the excavation process are analyzed by using the finite difference software FLAC3D，and the variation mode of the anchor cable tension and the supporting effect are discussed. The results show that the anchor cable tension presents remarkable time- dependent characteristics and is closely related to its spatial position；The thru-anchor cable in the middle partition wall effectively reduces the distribution range of the plastic zone of the rock wall. The research conclusion has important theoretical value and guiding significance for the design and construction of similar projects.

To overcome the drawbacks of previous displacement prediction models for step-like landslides such as the hysteresis and the unclear reliability of the prediction results of mutational displacements，a new hybrid prediction method of landslide displacement intervals is proposed. Firstly，the deformation of step-like landslides is divided into steady and mutational states by the combination of SOM network and K-means clustering. Secondly，on the basis of expanding the mutational state samples through the comprehensive application of the engineering geology analogy method and the adaptive synthetic sampling algorithm，an ensemble classifier for recognizing the landslide deformation states automatically is established adopting the random forest algorithm. Finally，an interval prediction framework considering the dynamic switching of landslide deformation states is constructed based on the Bootstrap-KELM-BPNN model. Taking Baishuihe landslide，a typical step-like landslide in the Three Gorges reservoir area，as an example，the dataset of XD01 monitoring point from June，2006 to December，2016 is explored to verify the effectiveness，accuracy and reliability of the proposed method.

During opencast mining of metal mines，hidden safety hazards caused by unknown underground airspaces are often encountered，and ground penetrating radar(GPR) detection of goaf is one of the commonly used means. Aiming at the misjudgment and omission in the interpretation of GPR detection airspace types，the alternating-direction implicit finite-difference time domain(CPML-ADI-FDTD) based on convolutional perfect matching layer and the related program were deduced，and the numerical simulation experiments of ADI-FDTD algorithm and finite difference time domain(FDTD) algorithm were carried out. The results show that ADI-FDTD algorithm can use a larger time scale to improve the forward modeling efficiency of ground penetrating radar. The forward simulation of a three-core arch roadway and its crossing roadway was established. Through spectrum，power spectrum and its instantaneous phase，the water-filling situation and the convergence of roadways were analyzed and the relevant interpretation criteria were obtained. Finally，An engineering example was deduced and interpreted，which was verified by the drilling results.

To confirm the mechanisms of different deformation and failure patterns of rock and soil masses in engineering constructions under complicated stress paths，taking the typical pale soil and surrounding rock in Zaosheng channel No. 3 of Yinchuan-Xi?an high-speed rail as the objects，triaxial shear test was done on soil samples under different stress paths using multi-stress path triaxial apparatus，and the pore size distribution characteristics of soils were acquired by low-field scanning MRI. Macroscopic and microscopic methods were integrated to make sure the soil mass deformation and failure mechanisms under different stress paths. The test results show that，under the conditions of both axial-loading and side-discharging stress paths，the stress-strain curves of the soil present a strain-hardening pattern，and that the initial confining pressure directly affects the variation trend of the stress-strain curve of the soil. Based on the normalization curve，the stress-strain relationships of the soil under the two kinds of stress path conditions conform to the hyperbola model，The p-q (average shear stress-generalized shear stress)curve of the soil shows a good linear relationship，and under the same stress path，the variation trends of the curves are tend to be identical with a parallel correlation in spatial position. However，the initial solidification confining pressure directly decides the position of p-q curve. The initial confining pressure plays a significant role on the improvement of the shearing strength of the soil. The cohesion and internal friction angle of the soil under axial loading are both larger than those under side-discharge in the same condition，especially for the cohesion. The initial confining pressure and the deformation of the soil have a good correlativity. Under the same deviatoric stress，the smaller the initial confining pressure is，the larger the deformation of the soil mass would be. The larger the peak strength of T2 is，the larger the scope of the relaxation time would be. It is observed that the content of small and medium pores of the soil is low while that of large pores is high. Under side-discharging with the same initial confining pressure，the peak strength of T2 is high and the relaxation time is long，which indicates that the content of medium and large pores in the soil mass is high. Under the same deviatoric stress，the deformation due to side-discharging would be larger. In addition，for the same axial strain condition，the samples show different pore information with different stress paths and initial confining pressures.

A model test of a four-anchor system applied in the earthen site with a size of 2 m×2 m×0.5 m was carried out through a self-developed pull-out system，and the failure mode and load-displacement relationship were studied. Based on the three-dimensional finite difference method，the displacement and stress fields of rammed soil，the axial stress of a single bolt and the stress distribution of the anchor-slurry interface were analyzed. The results show that the load-displacement curve shows elastic first and then plastic. The crack radius of the soil around an anchor is about 26 cm，and the cracks among anchors are connected with each other. The failure mode of the four-anchor anchorage system is a typical composite cone failure. The numerical simulation test reveals that the load-displacement distributions of the three selected measuring lines of the four anchor system including diagonal L1，sideline L2 and center line L3 are all symmetric parabola. The stress area of the four-anchor anchorage system is concentrated in the middle soil layer of the sample. With increasing the load，the shear stress of the bolt- slurry interface will transfer from the top to the bottom of the bolt，and the upper interface will debond. Under the influence of the ramming construction technology，the anchor group may separate along the soil layer. The research results have high reference value for the design of the anchor group system with wood bolts in earthen sites.

In order to study the structural deformation characteristics of shallow-buried large-cross-section loess tunnels strengthened by jet grouting piles and the choice of time for foundation reinforcement，indoor model tests and numerical simulations were performed，and the influence of piles and application time on the mechanical deformation characteristics of the tunnel structure was analyzed. The results show that the reinforcement effect of jet grouting piles to the foundation is remarkable and the deformation of surrounding rock at the bottom of the tunnel can be effectively reduced. In the case of full cross-section reinforcement by piles，the stress release of the surrounding rock is relatively sufficient with a large deformation. The displacement of the initial support easily exceeds the limit range in actual construction，and all the piles at the bottom of the tunnel are under pressure，which is beneficial to mobilize the effective bearing capacity of the piles in the later period. It is recommended that the full cross-section reinforcement scheme is adopted while the surrounding rock of the tunnel is stable. In the case of pile reinforcement in stages，however，the earlier closure of the support system is beneficial to the stability of the tunnel structure，but the piles in the middle of the bottom of the tunnel are in tension state and hence，are easy to break during the construction period. It is suggested that the second scheme can be used when the surrounding rock of the tunnel is unstable and at the same time，the piles should be reinforced. The research can provide a reference for the choice of time reinforcement of rotary jet grouting piles for loess tunnel base.

In order to study the effects of dome voids on the tunnel lining and the surrounding soil，both model test and numerical simulation were performed in this study. Taking the acceleration response peak and the frequency response function as the evaluation indexes，the dynamic response characteristics of the tunnel lining and the surrounding soil under single-point vibration loading were analysed for both cases with and without voids. Furthermore，the dynamic responses of the tunnel lining and the surrounding soil under moving train loads were examined by numerical simulation. The results show that the existence of the voids could increase the acceleration response of the tunnel structure and the surrounding soil. By calculating the frequency domain，it is found that the influence of the voids on the tunnel structure is mainly in the frequency domain above 90 Hz，and the maximum difference of the dynamic response of both cases could reach 10 dB. At the ranges of 0–90 and 150–190 Hz，the voids have little influence on the dynamic response of the surrounding soil，while at the ranges of 90–150 and above 190 Hz the voids will significantly increase the dynamic response of the soil. The influence of the dome voids on the dynamic response of the tunnel structure and the surrounding soil under the moving load is similar to that under the single point load. The dynamic responses of the vault and invert of the tunnel and the soil above the tunnel increase under moving loads. The influence of the dome voids on the internal force of the segment is small and limited to the near field. The axial force of the segment fluctuates at the position of the voids and is larger than that without voids.

In order to study the mechanical properties of frozen gravel-mixed clays，a series of uniaxial compression tests on frozen gravel-mixed clays were conducted with different temperatures and gravel contents. The test results show that the stress-strain response，uniaxial compressive strength，failure strain and elastic modulus are strongly affected by the temperature and gravel content of the specimens. Under uniaxial loading，the specimens present a typical pattern of brittle failure，and the smaller the gravel content is，the more significant the brittle failure characteristics are. The uniaxial compressive strength of the frozen gravel-mixed clay increases with decreasing both the temperature and the gravel content，and the variation degree is closely related to the structure distribution of clay-gravel. The failure strain decreases with increasing the gravel content while the effect of the temperature on the failure strain shows different characteristics under different gravel contents. The elastic modulus shows a quasi-linear increase with decreasing the temperature，and increases first and then decreases with increasing the gravel content. It is worth noting that the critical value of the gravel content depends on the temperature.

System sampling was conducted with an interval of 1 meter at Xiushidu section of Jingyang south plateau，Guanzhong Basin，Shaanxi. Direct shear test was executed under different or same vertical pressures，and microstructure and basis physical properties including dry density，moisture content and porosity were tested. The anisotropic characteristics of the shear strength of undisturbed loess were studied，and their formation mechanisms and influencing factors were also analyzed. The results show that the structural parameters of loess present different anisotropy characteristics as well as the shear strength. The vertical shear strength is generally greater than the horizontal shear strength for the layers above L7，while the ratio of the vertical shear strength to the horizontal shear strength for L7 and below layers is less than 1. The anisotropy degree of paleosol is larger than that of corresponding loess. The main influencing factors on shear strength anisotropy of loess-paleosol sequence are the porosity and the moisture content. The effect of the porosity on the horizontal shear strength is greater than that on the vertical shear strength，while the water content is opposite. The dry density is directly proportional to the shear strength but has little effect on the anisotropy of the shear strength. The shear strength anisotropy of natural loess is due to different arrangements of soil particles by aeolian deposition and rotation and rearrangement of particles during shearing.