Under the influence of anthropogenic and natural factors such as underground engineering，slope excavation and valley cutting，the rock mass stress will release at least in one direction，which induces complex stress redistribution of rock mass. Such unloading easily induces rock mass engineering disasters，and the shear failure due to normal stress unloading is particularly prominent. The direct shear test with gradually unloading the normal stress but keeping the shear stress constant was performed to simulate the shear mechanical behavior of rock mass induced by excavating and unloading. The influences of the angle between the flaw and the shear direction and the stress level on deformation，strength and fracture evolution of single flaw sandstone under unloading normal stress were studied. It is revealed that，with increasing the angle from 0°to 180°，single flaw sandstone in sequence shows shear failure，tension failure，mixed tension-shear failure and shear failure. In the process of unloading，the normal and shear displacements increase with increasing the initial normal stress but decrease with rising the initial shear stress. The unloading normal displacement decreases firstly and then increases with increasing the angle，while the unloading shear displacement is not sensitive to the angle. The unloading amount at failure respectively increases，decreases，and decreases firstly and then increases with increasing the initial normal stress，the initial shear stress and the angle. The specimen is most prone to unloading shear failure when the angle is 60°. The correlation between the failure mode and the angle was presented based on the analysis of the stress state of the crack surface. The research results enrich the basic theory of unloading rock mass mechanics and have reference value for the prevention and treatment of excavation disasters in rock mass engineering.

In order to analyze the effects of end friction and confining pressure unloading rate on rock mechanical parameters，the tri-axial confining pressure unloading tests of sandstone specimens under different end friction factors and unloading rates of the confining pressure were carried out by RMT–150B rock mechanics test system.The results show that，under the same end friction factor and initial confining pressure，the greater the unloading rate of the confining pressure is，the lower the failure confining pressure and the greater the differential stress at failure are，and that，with the same confining pressure unloading rate and initial confining pressure，the greater the end friction factor is，the lower the failure confining pressure and the greater the differential stress at failure are. The friction angle ? and the cohesion c of rock specimens increase linearly with increasing the end friction factor as a whole and increase overall at a decreasing rate with rising the confining pressure unloading rate and the same end friction factor. An end-friction(E-F) unloading strength criterion of rock including the end friction factor and the unloading rate was proposed，and the fitting analysis between the peak strength and the failure confining pressure of rock specimens by the criterion was performed. It is shown that the criterion can describe the strength of rock specimens under unloading confining pressure condition. Given the value of the end friction factor K，the E-F unloading failure strength envelope of rock specimens under different confining pressure unloading rates v can be drew out and then the strength parameters of rock specimens under different confining pressure unloading rates can be obtained.

In order to investigate the anisotropic properties of layered shale under dynamic loading，seven groups of samples with different bedding inclinations were cored from the black shale in Longmaxi formation，and dynamic compressive experiments at three strain rate levels were carried out by using the split Hopkinson pressure bar. The influence of the bedding direction on failure mode，strength and energy consumption characteristics of shale was investigated，and the failure mechanism of shale was revealed. A dynamic loading damage constitutive model of shale considering both initial and loading damage was established. The results show that the failure modes of shale with different bedding inclinations under dynamic loading can be divided into splitting tensile failure，shear failure and mixed failure. Splitting tensile failure is more likely to occur in the case of small or large bedding inclination，while shear or mixed failure is more prone to appear at a medium inclination. The compressive strength shows a trend of decreasing first and then increasing with increasing the inclination at three strain rates，which manifests an obvious bedding effect. The compressive strength also has a rate-dependent effect，which is in competition with the bedding effect. In other words，as the strain rate increases，the strength will increase as well but the strength anisotropy will attenuate. The change trend of the energy consumption characteristics with the inclination is similar to that of the strength. The value of the energy consumption is rate-dependent，but the energy consumption rate is not sensitive to the strain rate. The established damage model considering the coupling effect of rock mass structure and loading is simple in structure and clear in physical meaning. It is shown that the model is in good agreement with the experimental data，especially for the situation of medium to high strain rate without stress-strain rebound. The established model can be of benefit to more accurately describe the deformation and failure behavior of layered shale specimen under dynamic loading.

Adopting the assumption that the elastic modulus of the rock mesoscopic unit approximately conforms to the Weibull distribution，a rock damage constitutive model was established based on the strain energy density theory. A method for determining the rock homogeneous degree coefficient m and the reduction factor of the elastic modulus K0 was proposed using the AE(acoustic emission) energy signal and the rock longitudinal wave velocity，and the parameters were corrected as well. The uniaxial loading simulation was carried out by using the established damage constitutive model，and the simulation results were compared with the existing theoretical model and the uniaxial loading experimental results. It is shown that the proposed model can well describe the stress-strain relationship and acoustic emission conditions of specimens. The model was further used to simulate the repeated loading of plaster specimens and then to analyze stress，strain and acoustic emission characteristics，and comparison with the laboratory results was conducted. The research shows that the higher the homogeneous degree of the specimen is，the more obvious the characteristics of the brittle failure，and that the calculated results of m and K0，which are determined based on the AE signal and the rock longitudinal wave velocity，agree with the experimental results. The established model provides a new theoretical basis for comprehensively considering the effects of rock homogeneous degree and repeated loading on rock specimens.

A number of blasting gravel particles of limestone with the particle size ranging from 5 to 1 000 mm were randomly selected in the Hangudi quarry and then were classified into 5 groups according to the form. The particles outline projections were obtained by the 3D laser scanner and the self-designed measurement system，and the shape parameters of blasting gravel particles were calculated and analyzed by image processing technology and SPSS. The change law of the specific surface area of the 5 types of blasting gravel particles was analyzed，and the cumulative distribution curve of the specific surface area was drawn. The results show that the proportions of hexahedral，pentahedral，tetrahedral，flat and elongated，and irregular polyhedron particles are respectively 52%，17%，13%，13% and 5% in muckpiles. The hexahedron particles are most similar to a sphere in shape，followed by pentahedron and tetrahedron particles. The roundness and sphericity of 5 types of gravel particles increase with increasing the particle size，and the angularity is stronger as the particle size decreases. The surface texture of the gravel particles selected is similar and the specific surface area is in the range of 179.84–3.82 mm2/g with a specific charge of 0.37–0.38 kg/m3. The differences of the specific surface area between 5 types of gravel particles can be ignored in the case of the same particle size，and the specific surface area decreases exponentially with increasing the particle size. The cumulative distribution curve of the specific surface area can be obtained by using the gradation curve and the specific surface area curve.

The creep model is a main form to describe the rheological behavior of rocks. An important focus of research on rock creep is to develop a model with fewer parameters and better simulation performance. From the aspect of the physical meaning of fractional creep element，in this study，the creep process of materials was divided into elastic，viscoelastic and viscoplastic stages，and the variable-order fractional derivative was introduced to describe these three segments. In the case of the loading stress exceeding the yield stress，nevertheless，the creep damage accumulates and the accelerating creep occurs due to that microscopic cracks initiate，expand and evolve. Therefore，a damage coefficient was introduced to describe the non-linear strain at the accelerating creep stage considering the influence of damage evolution. A variable order non-linear visco-elastic-plastic creep model was proposed based on Scott-Blair fractional element and time-dependent fractional element and further generalized to three-dimension situations. A series of three-dimensional creep experiments of deep coal from Pingdingshan were analyzed by segment treatment，showing that the creep model based on the variable order fractional derivative is in good agreement with the experimental data. It is also proved that it is reasonable and reliable to regard the variable order of fractional derivative as a step function. In addition，the parameters of the model were determined on the basis of fitting the existing experimental results. The results show that the theoretical model proposed in this paper can well describe the creep properties of the material.

Stress-seepage coupling tests of sandstone under anhydrous and drainage conditions were conducted by using the automatic triaxial seepage experiment system. The stress-strain and permeability evolution curves of sandstone were obtained during the deformation process，which could better characterize the mechanical behaviors and permeability evolution response characteristics of sandstone under stress-seepage coupling，and the evolution law of deformation，strength and permeability of sandstone was investigated under stress-seepage coupling condition. The results show that the peak strength of sandstone increases with increasing the confining pressure，which shows that confining pressure effect is significant. The axial strain evolution law corresponding to the peak strength is in obvious accordance with the strength evolution characteristics under the anhydrous condition. The axial deformation of sandstone accords an exponential nonlinear growth relation with the confining pressure under the anhydrous condition，while the relationship between the axial deformation of sandstone and the effective confining pressure under drainage condition obeys a linear attenuation model. The pre-peak permeability of sandstone shows a“three-stage”evolution law of decreasing slowly firstly，then developing steadily and increasing sharply lastly，which respectively corresponds to the initial micro-crack compaction stage，linear elastic deformation stage and new crack propagation stage of the pre-peak stress-strain curve of sandstone. The permeability of sandstone also shows a three-stage evolution law including decreasing firstly and followed by increasing sharply and developing stably or increasing slightly under different working conditions，which also has a corresponding relationship with the volume compression stage，volume rapid expansion stage and volume slow expansion stage during the deformation process. The research conclusions can provide a theoretical basis for the prevention and control of water inrush accidents in coal mine and the stability controll of roadway surrounding rock.

The progressive failure of brittle schist with schistose planes shows anisotropy under compression loading. In order to study the anisotropic properties of crack initiation stress and crack propagation of schist and their correlations with micro factors，three types of quartz mica schist samples were selected. Firstly，the optical section analysis of these samples was carried out，and the differences among the characteristics of micro- fissures(pores) of three type samples were quantitatively analyzed. The results show that the mica minerals in the samples are easy to form heterogeneous layers by directional aggregation，and that the micro-fissures are mainly distributed along the edge of the mineral while the developmental direction of the defects in other parts is irregular. Then，uniaxial compression tests were performed on cylindrical specimens with different schistose angles，and the failure morphology and stress-strain curve characteristics of the specimens were investigated. Theoretical analysis of fracture mechanics shows that，when the compression loading is oblique to( =30°) and perpendicular to ( =90°) the heterogeneous layer，the initiation of rock fracture is respectively controlled by the directional micro-fissures and the irregular micro-fissures(pores) with dominant angles. The guiding and promoting effect of the weak edge of directionally aggregated minerals on crack growth is closely dependent on the loading direction，which results in the difference of macro shear failure modes of specimens with different schistose angles. Statistical analysis results of stress and strain data as well as the data reflecting micro properties show that the initiation stress and the initiation stress level of specimens have good regularity，which is related to the heterogeneity of rocks and the characteristics of micro-fissures(pores) such as distribution，quantity，size and nature.

Undercutting-erosion exists commonly in the breaking process of landslide dams. Due to the limitations of the formation mechanism and the gully terrain，however，many dams have a height difference in the transverse direction，which causes that the lateral erosion in the dam-breaking is unidirectional. The evolutional characteristics of landslide dams under the combination of unidirectional lateral-erosion and undercutting-erosion were studied by experiment test and numerical simulation. The test results show that，for the situation where the dam material completely comes from the gully，the failure scale of the breach slope resulted from the combination of unidirectional lateral-erosion and undercutting-erosion gradually increases. For a huge dam with a large height difference in the transverse direction and under the combination of unidirectional lateral-erosion and undercutting- erosion，a secondary landslide would occur with increasing the height of the breach slope. The formation of the secondary landslide was demonstrated by numerical simulation. Based on the theory of soil mechanics，an arc sliding model was proposed to predict the radius and failure area of the secondary landslide. The model has a certain practicality as the calculated value differs from the theoretical value by only 6.2%.

The fully mechanized mining method with a large mining height is widely applied in shallow thick coal seam of western regions in China，and the key stratum structure and its stability in fully mechanized longwall face with a large mining height have significant impact on the mine pressure and surrounding rock control. A calculation model of the goaf filling degree of the equivalent immediate roof including fully filling and generally filling types was established. Based on physical simulation experiments and UDEC numerical simulation，the stabilities of“high position and oblique step voussior beam”structure of single key stratum and“oblique step voussior beam and voussior beam”structure of double key strata in large mining height longwall face were analyzed，and the pressure mechanisms of the longwall face with single key stratum or double key strata were revealed. A formula for calculating the reasonable support resistance in the longwall face，taking the static load of the equivalent immediate roof and the instability dynamic load of the key stratum structure as the basic load and the additional load respectively，was put forward. An engineering example analysis indicates that the support resistance increases linearly with increasing the mining height，the break angle of the stratum，the thickness of the key stratum and the length of the key block，but decreases linearly with increasing the rotation angle of the key block，and that，when the mining height is the same，the support resistance increases with increasing the thickness of the equivalent immediate roof，and the static load of the equivalent immediate roof contributes mainly to the pressure of the hydraulic support in a large mining height longwall face. The reliability of the calculation formula of the support resistance was verified，and it is shown that the calculation formula can provide a reference for the support selection and ground control in similar longwall faces.

Aiming at the stability problems of the surrounding rock of roadways and the coal-rock in the tectonic area resulted from ordinary blasting in the reverse fault of the comprehensive excavation face，the coal and gas outbursts caused by blasting disturbance in the reverse fault structural zone were studied through theoretical analysis and comparison simulation experiments. Prevention measures such as changing the charge structure and using the directional cumulative blasting were proposed and applied in practice. It was found that the transmission and reflection of the blasting stress wave occur at the interface of coal and rock when the blasting stress wave propagates to the reverse fault structure area. The cumulative damage of blasting vibration causes the most serious damage to the interface of different coal and rock media，enlarges the damage degree and scope of coal and rock and provides a weak surface for the occurrence of coal and gas outburst even gas dynamic disasters. Directional cumulative blasting can concentrate the blasting action in the direction of rock and reduce the disturbance of the stress wave to the coal-rock in the structural area. Under the experimental conditions，the stresses in the energy accumulation and non-accumulation directions are respectively about 2 times and one third of those of ordinary blasting. The field application of directional accurately cumulative blasting in crossing hard rock faults in fully mechanized excavation face shows that，after blasting，the crack damage expands in the hard rock of the working face which meets the purpose of pre-weakening and the requirement of the rock breaking of the comprehensive excavator，and the coal-rock in the reverse fault structure area above the working face is basically complete which provides a guarantee for safe and rapid crossing the hard rock reverse faults in fully mechanized excavation face.

The Portland cement clinker and industrial wastes were selected to prepare the effective microfine cement-based grout(EMCG) adopting optimization methods of particle size distribution and hydration activity excitation. Through laboratory tests，the main features of EMCG such as flowability，viscosity，stability，initial/final setting time，strength and volume stability were studied，and the main properties of ordinary Portland cement 42.5(OPC)，microfine Portland cement(MC)，microfine sulphoaluminate cement(MSAC) and self- developed EMCG were compared. Based on mineral test methods of XRD and SEM，the hydration mechanism of EMCG was studied. Through grouting simulation experiments，the grouting strengthening property of EMCG on sand specimens was investigated，and different microcosmic reinforcement modes of slurry-rock for various grouts were compared. Field tests were performed to evaluate the plugging and reinforcement effects of EMCG on water-rich sand strata. The results show that the flowability of EMCG suspension is optimal when the water solid ratio(W/S)，and the amounts of fly ash and superplasticizer(SP) are 1.5∶1–2∶1，40%–50% and 1.5%–2.0% respectively and that the controlling factors of pumping stability are fineness and W/S. The strength and reinforcement effect of EMCG are the best，followed by MSAC and MC，and then OPC. The 7-day strengths of EMCG reinforced specimens are over 70% of the 28-day strengths. It is also shown that the EMCG suspensions have advantages of excellent groutability，pumping stability，setting controllability，volume stability，high strength，favorable hydration mineral，compact microstructure and so on，and hence，can effectively improve the integrity and stability of water-rich sand strata. Due to its high performance and excellent engineering applicability，EMCG is an efficient and excellent grout especially for anti-seepage and reinforcement of water-rich sand strata.

The physical and mechanical parameters of soft soils are the fundamental basis for the design of soft roadbed. However，the parameters of soft soils show strong regional characteristics due to various factors such as depositional environment. Based on a large amount of data from laboratory tests，vane shear tests and static penetration tests in the western central urban area of Zhuhai city(part A)，the engineering characteristics and parameters correlation of large-scale deep soft soil were analyzed. The results show that the water content of the soft soil in the central area of western Zhuhai is as high as 68%，which leads to a low shear strength and a high compressibility of the soft soil. The organic content ranging from 2.11% to 5.90% has little effect on the natural physical and mechanical properties of the soft soil. The strength indexes of CU-tests have a greater correlation with the water content than the strength indexes of direct shear tests，and the cohesion and the friction angle of triaxial shear tests are closer to the normal distribution. The shear strength indexes of the soft soil by laboratory experiments have no significant change with the depth. However，the shear strength of vane shear tests，and the hammer resistance and sidewall friction of static penetration tests firstly reduce and then increase with increasing the depth. The strength of the soft soil reaches the minimum at 2–4 m from the top of the soft soil layer and acceleratingly increases while the depth reaches about 6–9 m from the bottom of the soft soil layer. The in-situ tests can actually reflect the real situation of the soil strength than the laboratory experiments.

Slurry is a special remoulded soil without preconsolidation and in an unstructured state，and the initial water content before consolidation will affect the compression settlement and the strength of the slurry. To investigate the effects of the initial water content on the process and results of slurry consolidation，positive- loading GDS and vacuum-loading triaxial tests were performed on slurry samples with different initial water contents，and the relationships between the initial water content and soil factors ? and M in modified Cambridge clay model were also investigated based on the test results of previous works and this study. The research results show that the compression procedure of the slurry can be roughly divided into two stages including the initial structure formation stage and the regular compression stage，which differs from the natural deposited soil. With increasing the initial water content，? increases logarithmically while M decreases logarithmically. The empirical values of ? and M of the slurry were proposed in accordance with the research results to give a reference to the practical engineering and the following researches.

For power transmission towers along Qinghai—Tibet railway line which rans across permafrost regions，the biggest problem is to solve the long-term thermal stability of transmission tower pile foundation. In order to study the long-term cooling effect of thermal pipes applied to the pile foundation of transmission towers，a three-dimensional finite element analysis model of thermal pipe foundation was established based on frozen soil heat transfer theory and field test of thermal pipe foundation of power tower in the Wonkhu—Budongquan section of Qinghai—Tibet railway and considering global warming，frozen soil phase change，hydration heat release of concrete and change of thermal pipe power factors，et al. The power of thermal pipes and the temperature of the pile-soil system in 50 years were calculated and analyzed. The calculation results show that，in the first two years，the calculated and measured values are in good agreement with each other，which indicates that the proposed model can reasonably simulate the dynamic change of the temperature of the pile-soil system in this site. Within 30 years of the whole life cycle of the thermal pipe，the power of the thermal pipe decreases in a discontinuous wave form. The thermal pile foundation can effectively increase the cold reserve of the foundation and reduce the soil temperature. In the fifth year，the soil temperature around the pile is the lowest and the melting depth is the least. The thermal pile foundation can increase the permafrost upper table by 48 cm in the thirtieth year. In order to maintain the thermal stability of the transmission tower foundation，it is recommended that thermal pipes are replaced by new ones or that other engineering measures are adopted in the second year after the end of the life of the thermal pipes.

In order to study the longitudinal vibration characteristics of floating piles in saturated soil，a saturated virtual soil pile model based on Biot?s wave theory was proposed，and a coupled longitudinal vibration system of three-dimensional saturated layered soil，virtual soil piles and solid piles was established. The analytical solution of the displacement of saturated soil was derived by potential function method，and the vertical dynamic impedance at the pile head was obtained by using the pile-soil compatibility conditions and the transfer method of impedance function. The validity of the obtained solution was verified by degrading to existing solutions，and parametric analyses were performed to investigate the effects of the parameters of the saturated soil on the vibration characteristics at the pile head. The results show that，when the saturation of soil layers beneath the pile toe is remarkable and the drainage is poor，the saturated virtual soil pile model and the relevant analytical solution is more suitable to analyze the longitudinal vibration characteristics of floating piles. The longitudinal interlayer of surrounding soil has obvious effect on the amplitude of the dynamic impedance at the pile head，but the effect of longitudinal interlayer of soil beneath the pile toe on the dynamic impedance at the pile head can be ignored. The porosity of saturated surface surrounding soil has obvious influence only on the resonance amplitude of the dynamic impedance at the pile head，while the porosity of saturated soil beneath the pile toe has significant effects both on the resonance amplitude and the resonance frequency of the dynamic impedance at the pile head.

Aiming at the problems of strength anisotropy and strain localization of cohesive soils，Pietruszczak?s method considering microstructure tensor combined with stress invariance was developed to analyze the cohesion anisotropy of cohesive soils and introduced into Drucker-Prager constitutive model based on Cosserat continuum theory to realize dynamically updating of the cohesion with the change of the stress state. The relevant formulas were derived and the numerical implementation was carried out by means of the secondary development function of the finite element software-ABAQUS. The reliability and effectiveness of the numerical method developed in this paper were verified by comparison with the experimental results. Examples of uniaxial compression and passive failure of the retaining wall under plane strain condition were illustrated，and the reasonable values of the cohesion under different working conditions were proposed. It is shown that the cohesion anisotropy has an important influence on bearing capacity and deformation. Comparison with the calculation results by the classical continuum model indicates that the developed numerical model considering the strength anisotropy based on the Cosserat continuum theory can overcome the ill-posedness of mesh sensitivity and maintain the well-posedness of the strain localization problem.

The problem of deformation and instability of high-filled slopes in mountainous airports is a hotspot and a difficult point in airport research. Especially，the cooperative deformation mechanism of the combined support structure of slopes is one of the unsolved problems. In this paper，taking the #12 high fill of Panzhihua Airport as an example，3D visualization analysis was carried out based on the original design of the anchor cable-anti-slide pile-reinforced soil retaining wall treatment plan and by using BIM technology to design the model. Finite element simulation and experimental test were performed to analyze the influence of the cushion layer at the top of the pile on cooperative plastic deformation of the filling soil and the compound support system. Research results show that integrating the basic geotechnical parameters and information generalization of the survey data into the BIM model not only realizes the geological exploration most likely to be close to the actual site to ensure the scientificity and accuracy of the stratum parameters but also effectively solves the calculation of the arbitrary section cut design，and that space collision detection under complex conditions can be conducted effectively. It is pointed out that the development of BIM and finite element software interface program and the optimization of landslide engineering survey and design software for finite element calculation will become a new category to be improved. The mismatch between the rear anti-slide pile stiffness and the filling stiffness results in a plastic shear band inside the filling soil extending from the top of the pile to the slope in the case of high filling，which leads to settlement difference and stability problem of the filling soil. The cushion optimization design can well solve the problem of deformation non-coordination and provide an effective reference for similar engineering management. The influence of the cushion on the support system is mainly reflected in the performance of the anti-slide pile. Due to that the front pile is more sensitive to the overall response of the cushion，it is suggested to additionally set cushions to strengthen the shear force design of the rear pile. With increasing the fill height，the reinforced soil shows the external stability problem while the non-reinforced soil shows the settlement problem. The existence of the rear pile enlarges the possibility of external deformation of the slope due to the mismatch of the stiffness.