Conducting intermediate strain rate experiments is of significance to understand the rate effect of material mechanical characteristics in the full strain rate range. To overcome the drawbacks of current experimental apparatuses，a RMT401 intermediate strain rate triaxial test system with fully digitalized and servo-controlled functions was developed，which consists of three subsystems，i.e.，axial loading subsystem with the high-frequency response function，confining pressure subsystem with the fully digitalized servo-controlled function and data acquisition subsystem. Furthermore，the measurement of force and deformation could obtain the dynamic mechanical characteristics of rocks under intermediate strain rate loadings(10－2–100 s－1). To investigate the effects of the confining pressure and the strain rate on mechanical characteristics，a series of dynamic triaxial experiments on red sandstone samples under intermediate strain rate loadings were conducted in this study. The results show that the time to failure of the samples changes from several microseconds to several seconds，and that increasing the strain rate leads to an exponential decrease of the time while the increase of the confining pressure induces an increasing trend of the time. The change of the peak strength as a function of the strain rate can be depicted by a power function formula. As for the effect of the confining pressure，the fitting effects of the peak strength of red sandstone by both Mohr-Coulomb and Hoek-Brown failure criteria are both good，yielding the cohesion of 22.8 MPa，the internal friction angle of 38° and the material constant m of 12.1. The ultimate failure patterns mainly include two types including single failure plane pattern and double failure plane pattern. As increasing the strain rate and the confining pressure，the failure pattern gradually changes from the single failure plane pattern to the double failure plane pattern. The mean values of the failure angle for the double failure planes are 58.3° and －58.2°，respectively，which are consistent with the calculation values of = ±64° by the Mohr-Coulomb theory.

In order to investigate the influence of drying-wetting cycles and the fissure angle on the mechanical properties of carbonaceous shale with pre-existing fissures，uniaxial and triaxial compression tests on carbonaceous shale with pre-existing fissures after drying-wetting cycles(0，5，15 and 20 times) were carried out. The results show that the peak strength，cohesion and internal friction angle of carbonaceous shale gradually decrease with increasing the number of drying-wetting cycles，which manifests an obvious drying-wetting deterioration effect. The degree of deterioration is as follows：peak strength＞cohesion＞internal friction angle. The strength deterioration degree of carbonaceous shale after drying-wetting cycles gradually decreases with increasing the confining pressure，which indicates that the confining pressure has an inhibitory effect on the drying-wetting deterioration effect. The peak strength，cohesion and internal friction angle of carbonaceous shale show a trend of decreasing first and then increasing with increasing the fissure angle，which manifests an obvious angle effect. However，the angle effect and drying-wetting deterioration effect are mutually inhibited. In other words，as the number of drying-wetting cycles increases，the peak strength，cohesion and internal friction angle will decrease and the angle effect will attenuate. By introducing two mechanical parameters(and ) into the Drucker-Prager criterion，a strength criterion was established considering the drying-wetting cycles and the fissure angle，which can well describe the drying-wetting deterioration effect and angle effect of the strength. The research results can provide a reference for the strength estimation of carbonaceous shale in engineering practice and the stability analysis of slopes.

In order to study the mechanical properties and seepage wetting law of coal and rock under the complex stress environment of deep coal seams，a dynamic monitoring test system for the hydraulic wetting range of coal and rock under true three-dimensional stresses is independently developed. The system is mainly composed of a stress loading system，a hydraulic servo system，a data acquisition and control system and an acoustic emission monitoring system. The system has the capabilities of carrying out experimental research on coal and rock under different ground stresses，different fluid pressures，different mining stresses，different temperatures and other multi-field coupling conditions，conducting the hydraulic fracturing test of coal and rock under different ground stresses，different fluid pressures and different temperature conditions in order to study crack initiation position and crack propagation of coal and rock，performing the anisotropic seepage test of multi-phase fluid including water and gas under different geostresses and different mining stress to study the influence of the anisotropy of samples on the seepage effect in-depth，and carrying out wetting test research of liquid phase fluid in porous media under different ground stress and mining stress conditions for analyzing the dynamic wetting range and wetting process of the liquid phase fluid under different fluid pressures combined with acoustic wave test. The innovation and advancement of the system include fully sealed design. Specifically，a spherical acoustic emission probe is installed at the front end of the water injection pipe，an acoustic wave sensor is installed on the pressure head to receive excitation signal from the spherical acoustic emission probe，and the sample is individually fixed and sealed with a detachable indenter，ensuring the overall sealing of the sample under the normal operation of the acoustic emission system. The accuracy and reliability of the system are verified through a series of tests. This system provides a new method for studying the law and change mechanism of the whole process of coal and rock hydraulic fracturing，seepage and wetting under the condition of multi-field and multi-phase coupling.

As a basic component of the shear strength of rock joints，the accurate acquisition of the basic friction angle is the prerequisite for evaluating the shear strength of rock joints. Generally，the basic friction angle is considered to be a parameter that can be easily obtained. However，many recent studies have shown that the basic friction angle varies significantly with the nature of the sample，the processing method and the measurement method. This paper summarized the research results of the basic friction angle from the aspects of the shear strength model，the mechanical mechanism，the acquisition method and research trends. The results show that the basic friction angle，involved in most shear strength models，lacks a clear definition and a determination method，and that，in particular，there are few studies on improving and optimizing the shear strength model based on the basic friction property of rock joints. It is generally believed that the mineral compositions and morphological characteristics of rock joints play a decisive role in the mechanical mechanism of the basic friction angle，but the influences of the dilatancy effect and the size effect on the basic friction angle are controversial. Tilt test，direct shear test，push-pull test，triaxial test and rebound test are the main experimental methods for obtaining the basic friction angle，but the reliabilities and the applicable conditions for these methods are still unclear. Alghouth at present the basic friction angle has been studied from the mineral composition and structure，roughness，size effect，sample processing technology，test conditions，etc.，further investigations are needed from the perspectives of petrology，micro-roughness and scale effects. It is also pointed out that there is a research trend of further improving the test methods of the basic friction angle by considering the normal stress，shear rate，temperature and humidity.

Taking a bedding rock slope and a toppling rock slope in the Zheduoshan tunnel area as reference，the shaking table test was designed and carried out. The differences of seismic dynamic responses of the two kinds of slopes are systematically compared from the aspects of failure phenomenon，PGA amplification factor and time-frequency characteristics. The results show that the failure of the bedding slope is prior to that of the toppling slope，which indicates that the seismic stability of the toppling slope is better than that of the bedding slope. The damage of the toppling slope is mainly concentrated on the top of the slope surface，while the failure mode of the bedding slope can be divided into three stages of cracking of the slope waist，formation of the sliding surface at the trailing edge of the slope and collapse and instability of the slope. The acceleration responses of the bedding and toppling rock slopes show obvious “elevation effect” and “surface effect”. Under the action of 0.1 g–0.5 g amplitude seismic waves，the PGA amplification factor of the bedding slope is greater than that of the toppling slope. With strengthening the ground motion，the bedding slope is destroyed before the toppling slope，and its acceleration amplification effect is weaker than that of the toppling slope. Hilbert spectrum and Hilbert marginal spectrum clearly describe the propagation characteristics of the seismic energy in time-frequency domain of bedding and toppling slopes. The distributions of the seismic energy in time-frequency domain of the two kinds of slopes are similar，and the difference is mainly reflected in the amplification effect along the elevation. In addition，according to the Hilbert marginal spectrum，it is identified that the seismic damage of the toppling slope is mainly concentrated at the slope shoulder，while that the damage of the bedding slope occurs at the slope waist where a shear slip surface will form，which is basically consistent with the phenomena observed in shaking table test.

In order to improve the stability of tailing-cemented backfill of a gold mine and to ensure the backfill effect of the goaf of the mine，the early mechanical properties and damage characteristics of tailing-cemented backfills with different fibers(polyacrylonitrile fibers，glass fibers，polyacrylonitrile fibers and glass fibers mixed fibers) were studied，and a damage constitutive model of the tailing-cemented backfill with different fibers was obtained by uniaxial compression test. The test results show that the uniaxial compressive strength of the tailing-cemented backfill with glass fibers is the largest，followed by mixed figers，polyacrylonitrile fibers and fibreless. The fibers have obvious interference and retarding effect on the crack propagation，making the cracks more and smaller，and greatly enhance the toughness of the cemented tailings backfill. The crack blocking effect of mixed fibers is significantly better than that of single fibers. The tailing cemented backfill with fibers does not completely lose its load-bearing capacity after the peak，and continues to carry part of the compressive-shear stresses due to its high toughness. A theoretical damage constitutive model of tailing-cemented tailings backfills with different fibers was built，and the model curve was obtained through correcting the damage variables by six different damage parameters. Finally，the theoretical model was verified through experiments. It is revealed that the stress-strain curves from the model and the experiments are in good agreement，showing that the established theoretical model has certain reference value for the analysis and evaluation of the mechanical properties of tailing-cemented backfills with different fibers.

In order to study the mechanical and permeability characteristics of sandstone under different saline environments when CO2 is stored in deep saline layers，conventional triaxial compression，acoustic emission monitoring and permeability tests were adopted to investigate CO2 permeability，strength and deformation behaviors of sandstone specimens under different confining pressures，and the action mechanism of saline solution on the permeability and strength behaviors of sandstone specimens under different confining pressures was revealed by combining with the microstructure. The results show that the permeability，peak strength，damage threshold and elastic modulus of saturated sandstone specimens with different solutions are lower than those of dry sandstone specimens. Compared with the saturated specimens soaked in pure water，the permeability of the saturated sandstone specimens soaked in 5%NaCl or 5%K2SO4 is decreased，and the peak strength，damage threshold and elastic modulus of the saturated sandstone specimens soaked in 5%K2SO4 are increased while there are no obvious changes for the strength and deformation parameters of saturated sandstone specimens soaked in 5%NaCl. The failure modes of the saturated sandstone specimens soaked in different solutions are different，mainly resulted from that the sandstone specimens soaked in saline solutions have more associated cracks. Through observing the microscopic structure，it is found that there are erosion and dissolution holes on the surface of the sandstone specimens after soaking, and that there are crystals on the surface of the saturated specimens soaked in brine solutions. NaCl crystals are randomly distributed on the surface of the specimens，while K2SO4 crystals are accumulated on the surface of the specimens.

This paper proposes a novel method，named as unified pipe-interface element method(UP-IEM)，for modelling the hydraulic fracture propagation in a permeable porous medium. There are two unified processes including the combination of the fluid flow and the fracture propagation into 1D pipe element and the unification of the matrix pipe and the fracture pipe as a same pipe with different hydraulic conductivities for solving the fluid flow using the same mathematical equations. UP-IEM overcomes the difficulties to consider the rock matrix permeability of traditional discrete fracture network model. The interface element is introduced to simulate the fracture propagation. For UP-IEM which has high efficiency，neither local crack propagation criteria nor tracking algorithms are required compared with traditional FEM and DEM. The deformation of the rock matrix is described by poroelasticity theory and effective stress concept. The cohesive zone model is used to simulate hydraulic fracture propagation and the contact-frictional model is utilized to model closure and slip of natural cracks. Besides，the fluid flow in porous medium and fractures is solved using Darcy law. A semi-explicit frame is built to solve the hydro-mechanical coupling problems. Three typical examples，including Terzaghi's consolidation test，unsymmetric four-points bending test and KGD model，are simulated. The simulation results are compared with analytical solutions and experimental results，verifying the accuracy and applicability of UP-IEM simulating fluid flow，fracture propagation and hydraulic fracturing. Furthermore，the hydraulic fracturing in models with single natural fracture and complex fracture network is simulated，analyzing the interaction between hydraulic fractures and pre-existing fractures and discussing the influence of in-suit stresses on the fracture propagation path. These examples show that UP-IEM could effectively simulate the hydraulic fracturing in discrete fractured rock.

The theoretical solution of excavation-induced stress redistribution is the mechanical cornerstone of safe mining and stability maintenance of surrounding rock in deep. Based on a comprehensive review of mechanical models of stress redistribution，it is found that the advantages and disadvantages of theoretical solutions based on elastoplastic model coexist. The advantage is that the universality of the built mechanical element strictly guarantees the rigor of the theoretical solutions，and the disadvantage is that the continuity definition of the mechanical element hinders the obtainment of the discontinuous solution of excavation-induced stresses. Although the introduction of probability models may provide a new idea for solving the mining-induced stress redistribution，the solution by simply introducing the probability model cannot guarantee the uniqueness due to the mapping problem. By comparing and verifying the stress redistributions respectively considering three probability models of Weibull function，Gumbel function and Gamma function，it is found that an unavoidable deviation between the probability model-based solutions and the measured values，which is caused by the non-uniqueness of the probability models. Finally，taking the connectivity probability density of fracture field as a bridge and introducing percolation theory into the parallel bar model，a concise percolation solution of mining-induced stress redistribution is obtained. Comparisons between the measured results of several mining areas and the predicted values of the percolation model verify that the proposed percolation model is reliable and simple in form.

In order to investigate the change of the shear strength of rock joints with saturation，artificial rock joints with various roughness were reproduced by mixing cement，sand，fly ash and water at a mass ratio of 1∶3∶0.4∶0.55 based on 3D-laser scanning and 3D-printing technologies，and the saturation of the joints was controlled according to the calculated joint void volume. Subsequently，a series of direct shear tests were carried out on the reproduced joints with various roughness and saturations under a constant normal stress of 0.2 MPa. Experimental results indicate that the average peak shear strength of rock joints decreases by 28.4% when the saturation increases from 0 % to 100 %，and the peak shear strength of the rock joints with a JCR of 12.9，10.1 and 7.3 respectively decreases by 35.7%，28.5% and 16.1%. Besides，the residual shear strength also reduces with increasing the saturation，and the reductions dependent on the joint roughness range from 7%–12%. Further analysis shows that the weakening of the shear strength of rock joints arises from the mechanical effect and lubricating effect of water exerted on the rough joint surface，and that，as the joints get rougher，the water-rock interaction area becomes greater，inducing a higher deterioration in mechanical properties. According to the findings from this study，it is emphasized that the effect of the water saturation on the degradation of the shear strength should be analyzed when designing rock mass projects.

The application of the micro-seismic monitoring technology in mines is increasing，but the automatic identification of effective signals and noise signals has not been realized，which seriously restricts its application and popularization. Six main pattern categories in the mine strong noise environment，including drilling，trackless equipment running，mine shaft dumping，electromagnetic interference，blasting and effective signal，are investigated，and the effective signal patterns are divided into two subsets of small-energy events and large-energy events. The generation mechanism of each pattern class is studied in detail. By collecting a large number of samples of each pattern class，the identifying characteristics extracted for the above six pattern classes are respectively the waveform interval time，the waveform duration，the combination of the total duration with the number of individual events，the waveform duration or the main frequency，the combination of the waveform duration and the main frequency，and the waveform duration and the exclusion method. The distribution probabilities of the recognition characteristic values are calculated and counted by using the pre-processing method. A decision function with excellent recognition performance is constructed，and an automatic pattern recognition algorithm of mine micro-seismic waveform characteristic is established. Based on the above algorithms，a software of automatic pattern recognition is developed. Through the field test in a typical mine，the recognition accuracy of the effective signal of the developed algorithm is 90.8%，showing a good field application.

Broken strata landslide is one of the typical disaster types in southwest mountainous area of China. The landslide material is mainly composed of broken particles and has strong fluidity and disaster-causing ability. The study of particle distributions in the landslide area is helpful to disaster range prediction and disaster prevention. Based on UAV photography and image recognition technology，this paper introduced the correction coefficient of the projection area，Ki，to realize non-uniform plane projection and deformation correction，aiming at the problem of particle projection deformation caused by the angle between the projection plane and the terrain，and so as to obtain the statistical characteristics of particles more accurately. Taking the Aerzhai landslide in Longxi Township，Wenchuan County on April 8，2018 as an example，the number of landslide particles，location parameters，projection areas and correction areas were obtained by the proposed method. The characteristics of the landslide particle size and the particle spatial distribution，the longitudinal and transverse motion patterns of the landslide，the spatial distribution of particles in vertical and horizontal directions，the crushing and sorting of particles during longitudinal motion，the potential energy driving characteristics and the inertia advantage of huge particles were analyzed. The results show that the accumulation area of Aerzhai landslide has higher proportion of small particles and better sorting than the sliding source area. With increasing the moving distance，the proportion of small particles increases and the sorting becomes better. The motion of huge particles with a ratio of 2.4% has significant potential energy driving characteristics，and the distance of movement is farther than that of small particles. At the same time，huge particles also have obvious inertial advantage，concentrated in the central area of landslide accumulation.

Conventional vacuum preloading technology has engineering problems such as easy clogging of drainage plates and poor reinforcement effect when strengthening ultra soft soil foundations. In view of these problems，a new type of vacuum preloading method，named as alternating vacuum preloading method，was proposed in which the vacuum pressure is alternately applied to the drain plate in time-sharing mode. In order to explore the reinforcement effect and the corresponding influencing factors of the alternate vacuum preloading method，laboratory model tests were carried out on the ultra soft soil in Tianjin Binhai New Area. The research results show that，compared with the conventional vacuum preloading method，the alternating vacuum preloading makes the soil particles move alternately，which can effectively prevent the formation of clogged mud layers and improve the reinforcement effect. The size of the vacuum pressure and the timing of alternation have a significant impact on the reinforcement effect of the soil. Using a smaller vacuum pressure，or carrying out alternation at the beginning of the formation of the silt mud layer，can effectively improve the reinforcement effect of the soil. It is revealed that the drainage，the settlement and the vane-shear strength can be increased by 6.25%–14.82%，4.28%–7.73% and 4.53%–18.7%，respectively.

The ultimate drainage strength and the peak frictional angle of sand are significantly state-dependent and anisotropic. To form the relationships between the ultimate state of sand(i.e.，the ultimate strength and the peak frictional angle) with the initial state parameter and the rotation angle of the principal stress axis，first，the adopted state-dependent anisotropic constitutive model of sand is verified by simulating drained triaxial tests and drained hollow cylindrical torsion shear tests. Then，the relationship between the peak friction angle and the initial state parameter under drained triaxial compression conditions is obtained based on the results of the constitutive simulations. By adopting the drained triaxial loading path，a simplified formula for calculating the ultimate strength under drained triaxial conditions is established. Furthermore，drained hollow cylinder torsional shear tests under uniform internal and external pressures are simulated and the relationship between the peak friction angle and the rotation angle of the principal stress axis is obtained. By employing the drained torsional shear path，a simplified calculation method of the ultimate drainage strength，considering the rotation of the principal stress axis，is established. The effectiveness of the simplified method is verified by comparing the ultimate drainage strengths from the simplified method，experiments and simulations under drained triaxial and torsional shear conditions.

The destruction of natural soils occurs when the external loading energy is greater than the limit deformation energy of the soils，thus，a structure parameter in terms of the deformation energy is more suitable to describe the essential characteristic of soil structure. The confined compression tests were conducted on compacted remolded and undisturbed loess samples with various water contents and dry densities from the Taohua Hill，Yan¢an city. Test results suggest that there is an obvious piecewise linear relationship between the void ratio e and the vertical pressure P in -lgP bi-logarithmic coordinate system. Based on this，a structure parameter in terms of the mapping energy was derived according to the strain energy density theory，and further extended into complex loading conditions. Moreover，the verification of the proposed parameter was carried out based on the oedometer tests on remolded and undisturbed soils with different water contents，dry densities，burial depths and particle size distributions，as well as the isotropic compression tests with various water contents. The results show that the proposed parameter has a clearly physical meaning and is able to represent the soil structure quantitatively and accurately under diverse experimental conditions.

The friction characteristics of geotechnical granular materials are closely related to the roughness of the particle surface and the particle shape. The roughness surface will hinder the relative sliding between particles while the irregular particle shape will hinder the rolling between particles. The conventional triaxial tests with different values of the sliding friction coefficientand the rolling friction coefficientwere carried out to study the influence of the inter-particle contact friction on the macro and micro mechanical properties and energy evolution of granular materials by using linear-based rolling resistance model in discrete element method(DEM). The results show that for the materials with similar particle shape(the same)，the dilatancy and the peak strength increase with increasing the particle roughness，while the residual strength changes little. For the granular materials with smooth surfaces，the irregularity of the particle shape has little effect on the peak and residual strengths. For the coarse granular materials，however，the irregularity of the particle shape can obviously improve the peak and residual strengths. From the microscopic perspective，the influence of the surface roughness and the particle shape on the proportions of sliding and rolling contacts，as well as the evolution of the micro energy，were analyzed during shearing.

Internal erosion is a major cause of failures of many infrastructures such as dikes，embankments and dams. At present，studies on internal erosion of sands fail to consider the influence of cyclic loading and cannot describe the migration of fine particles quantitatively. To this end，a series of cyclic loading-controlled seepage tests were conducted on two dyed sands with different particle size distributions to explore the hydraulic response mechanism during internal erosion，and to describe the particle size distribution and the detailed amount of the lost particles after the tests. The results show that with the coupling effect of cyclic loading and ascending water head，specimen A，evaluated to be stable by soil stability assessment methods in the literature，presents a certain amount of particle loss and then reaches a new equilibrium state，while specimen B assessed to be unstable continues to lose fine particles accompanied by the permeability coefficient increasing. It is also indicated that the average particle size of the migrated particles tends to be greater and the depth of the migrated particles tends to be larger with increasing the hydraulic gradient. Under the coupling action of the cyclic loading and the water head，the pore water pressure in sand specimens fluctuates，forming an oscillating hydraulic gradient and therefore affecting the internal stability of the soil samples. The research results deepen the understanding of the internal erosion characteristics of sands and provide theoretical and experimental support for studing the development mechanism of related diseases.