The concept，classification method and structure type of early slope structure are reviewed and discussed. In order to improve and to unify the structural classification system of slopes，this paper further explains the concept of slope structure. Based on the influencing factors such as formation lithology，development degree of weak structural planes and their combinations with the slope surface，rock mass integrity，and deformation and failure characteristics，a unified classification system of slopes based on slope stability evaluation is proposed，including 5 categories of massive structure，quasi massive structure，non block structure，cataclastic structure and deformation structure，and 21 sub categories. The classification method highlights the control effect of weak structural planes and their combinations with the slope surface on the slope stability，and divides the traditional layered structure into two different types of quasi massive structure and non massive structure according to the slope stability attribute. The soil slope is incorporated and the type of deformation structure is added in the classification system. The classification basis is reasonable，easy to understand and practical. It has important guiding significance for slope geological survey and slope stability zoning evaluation，instability failure mode identification and stability analysis methods，as well as the selection of excavation and treatment design schemes.

To investigate the effects of the tensile and compressive strengths of rock on the rock slope stability，a geometric relationship between the MSDP(Mises-Schleiche Drucker-Prager) strength envelope and the corresponding Mohr circle is established，and an expression of the MSDP criterion in the t-sn space is derived. Then，a theoretical calculation method of the safety factor for the plane sliding rock slope is proposed based on the limit equilibrium method，and the mechanical model and the corresponding analytical solution of the safety factor for the rock slope are verified by engineering practice. Finally，the effects of some factors(e.g. slope angle，internal friction angle，compressive strength，tensile strength，tensile crack depth，weight and inclination of sliding surface) on the safety factor are discussed. The results indicate that the slope safety factor evaluated based on the MSDP criterion is higher than that by the traditional M-C criterion，that the slope stability can be improved by considering the tensile and compressive strengths of rock and the effect of the compressive strength on the slope stability is more significant than that of the tensile strength，and that the slope safety factor has a good quadratic function relationship with the internal friction angle，the compressive strength，the depth of tensile cracks and the sliding surface dip angle，and a good linear relationship with the tensile strength and the weight.

Rockburst has become one of the most serious threats in deep hard rock engineering. Accurately evaluating the risk of rockburst can avoid unnecessary casualties and property losses. In order to understand the research status of long-term and short-term rockburst risk evaluation methods in deep hard rock，the relevant literature at home and abroad is reviewed. First，the long-term and short-term rockburst risk evaluation methods are summarized and classified. Then，the advantages and disadvantages of existing evaluation methods are analyzed. On this basis，the future development directions of long-term and short-term rockburst risk evaluations are further proposed to improve the evaluation level of rockburst risk in hard rock. The results show that the long-term rockburst risk evaluation methods can be summarized as single-index empirical criterion method，multi-index aggregation method，uncertainty analysis method，comprehensive ranking method，machine learning method，numerical simulation method and catastrophe theory，and that short-term rockburst risk evaluation methods can be summarized as precursory characteristics method of time series，fractal theory，machine learning method，probabilistic warning method and empirical method. Different evaluation methods have their own advantages，disadvantages and application conditions. In practice，the evaluation methods can be comprehensively selected based on specific engineering characteristics and existing data.

During anchorage construction，stirring the resin in the borehole is a hidden work，so it is not easy to master the distribution of the resin after stirring. In this paper，through the combination of theoretical analysis，numerical simulation and laboratory experiments，the influence of the wedge-shaped end of rebar bolts on the stirring effect of the resin is analyzed. The theoretical analysis shows that the cutting angle of the wedge-shaped stirring end has a great influence on the force acting on the resin and the stirring effect. The wedge-shaped stirring end of the bolts will make the top of the bag of the resin concave and increase the rotation force of the resin when the bolts rotate，which will help to destroy the bag of the resin and to improve the fluidity of the resin. Numerical simulation shows that，in the case of a double wedge angle of 75°，ribs at the top of the “straight” type bolts and the offset C = 0，the stirring effect of the resin above the wedge-shaped stirring end of the bolts is more uniform，the flow velocity is larger and the diffusion range in the borehole is wider. At the same time，it is helpful to improve the stirring efficiency of the resin by adding a groove at the “straight” tip of the wedge-shaped stirring end of the bolts. According to the anchoring performance test of the bolts，it is found that after the stirring end of the bolts is added grooves，the average value of the peak pull-out force is increased by about 15% and by about 36% compared with the average peak pull-out force of the common bolts. The research results have certain theoretical and engineering application values for improving the anchoring quality and performance of bolts.

In order to explore the critical slowdown characteristics and instability precursors of fine sandstone with prefabricated fractures under uniaxial loading，uniaxial loading and synchronous acoustic emission(AE) were carried out on fine sandstone samples with different prefabricated fracture angles using MTS loading system，and the acoustic emission characteristic parameters(RA/AF value，duration and rising time) in the damage and failure processes of rock were systematically analyzed based on the critical slowing down theory method. The results indicated that, under uniaxial loading，there will be a dispersion fluctuation phenomenon when the fine sandstone with prefabricated cracks changes from fracture damage to instability failure，that is，an obvious critical slowing down phenomenon，which is manifested by the sudden increase of the variance and the autocorrelation coefficient. The window length and the lag step have no significant effect on the precursory characteristics of the variance，but have a great influence on the volatility of the autocorrelation coefficient. When the window length and the lag step are small，the autocorrelation coefficient fluctuates greatly. When the window length and the lag step length are large，the autocorrelation coefficient fluctuates less. The variances of RA/AF value，duration and rising time are the same as the mutation time of autocorrelation coefficient precursor signals，and the waveform fluctuations are also similar，which appears in the irreversible plastic deformation stage of new microcrack initiation. Therefore，the variances of RA/AF value，duration and rising time，and the increase of the autocorrelation coefficient of AE can be used as the precursor characteristics of instability. The autocorrelation coefficient fluctuates greatly compared with the variance. Therefore，the variance can be used as the main criterion for rock damage to instability，and the autocorrelation coefficient can be used as the auxiliary criterion. In summary，the research results can provide important reference for the short-term monitoring and early warning of rock brittle failure with sudden strong and weak external deformation such as landslide，collapse，mining and tunnel.

Since the prestressed anchors were widely used in concrete dam reinforcement，their long-term durability has been increasingly concerned. To validate the durability of the prestressed anchors in the high alkaline environment of dam bodies，the field exhumation of anchor cables which have served for nearly 30 years in old Fengman dam was performed during the demolition progress of the dam，and the anchor samples were collected and tested in the laboratory for evaluating the durability performance of the prestressed anchors in Fengman old dam including the corrosion appearance and corrosion degree，and the chemical and mechanical properties. The electrochemical test was conducted to analyze the anchor corrosion resistance and to assess the causes of the anchor corrosion. The main conclusions are summarized as follows：(1) the average corrosion rate of the bonded prestressed anchors in service for nearly 30 years is higher than 2%，which indicates that the alkaline environment in concrete dams can not effectively inhibit the corrosion of the prestressed anchors. (2) The unbonded anchors in the dam body have better performance in corrosion resistance than the bonded anchors，and (3) after nearly 30 years¢ service，the elastic modulus of 51.3% anchor samples is below the limit of “the Steel Strand for Prestressed Concrete”(GB/T 5224—2014).

In order to explore the mechanical properties of the reservoirs during the CO2 displacement coalbed methane exploitation process，CO2 adsorption experiments under different pressures(4，6，8，and 12 MPa)，Brazilian disc splitting experiments，low temperature nitrogen adsorption experiments and fracture analysis were carried out on bituminous coal samples. The influence of CO2 state and anisotropy on mechanical response of bituminous coal to progressive failure was studied. The results show that the Brazilian splitting strength(st) and modulus(ET) of bituminous coal decrease first and then increase under the influence of CO2 adsorption. Under 8 MPa supercritical CO2 adsorption，st and ET decrease by 49.8% and 33.9% respectively. The order of st of three types of bituminous coal samples is divider type followed by arrester type and short converse type. With increasing the CO2 pressure，bituminous coal shows a transformation law of failure characteristics from sudden instability to gradual instability and to sudden instability. At the same time，the CO2 adsorption effect weakens the matrix and the bedding plane of bituminous coal，which makes the failure path of anisotropic bituminous coal more complicated with increasing the CO2 pressure. The failure path can be divided into single failure，multi-source failure and fragmentation failure tracks，which can be further divided into twelve sub categories. The above-obtained results are due to the differences of CO2 adsorption，organic matter extraction，dissolution and compression under different phase states and pressures as well as the corrosion of CO2 acid fluid. The specific surface area，the total pore volume and the pore size distribution uniformity of bituminous coal are changed by the interaction of CO2 and bituminous coal. The change of the micro structure is related to the macro mechanical properties，which affects the mechanical properties and failure characteristics of bituminous coal. The research results can provide certain reference value for reservoir reconstruction，stability evaluation and exploration of high-efficiency production technology in CO2 displacement coalbed methane development project.

This paper proposed a temporal coupled explicit-implicit time integration algorithm to improve the computational efficiency of the numerical manifold method(NMM) for seismic stability analysis of rock slopes. The algorithm includes a coupled time integration scheme，a phase transfer criterion and an associated contact criterion. To calibrate the proposed algorithm，a block sliding along a slope under seismic excitation and a block rocking under half-sine pulse shaking were simulated. The algorithm was also applied to analyze the dynamic stability of an open-pit mine slope excited by the input earthquake wave. The simulated results by the algorithm are in good agreement with those obtained by the traditional NMM，whereas the computational efficiency of the former is improved significantly to 5.67 times more than that of the latter. The proposed coupled time integration algorithm has the potential to be applied to larger engineering problems.

In order to study the shear strength features of rock joints under constant normal stress conditions，irregular sandstone and granite joint specimens were prepared by using a splitting method. After obtaining the morphological parameters of rock joints with a three-dimensional topography scanner，the direct shear tests of rock joints under different normal stresses were carried out by using the RDS–200 rock joint shear test system. Based on the relationships between the peak dilatancy angle and the normal stress，and between the joint morphology and the joint deformation resistance，an empirical formula for the shear strength of irregular rock joints was proposed. On the whole，the peak shear strength，the peak shear displacement and the pre-peak shear stiffness increase with increasing the normal stress，while the contribution of the initial shear dilatancy angle to the peak shear strength decreases with increasing the normal stress. The initial shear dilatancy angle is characterized by the contour area ratio，a 3D morphology parameter of the joint surface. Based on the consideration of that the peak dilatancy angle is negatively correlated with the normal stress but positively correlated with the deformation resistance of the rock joint，an empirical formula for the peak shear strength of the rock joint was proposed to describe the peak shear resistance of the rock joints in two shear failure types. Compared with the existing empirical formulae of the rock joint shear strength，the new proposed empirical formula has a good prediction accuracy，which may provide a strong support for conveniently estimating the rock joint shear strength in engineering practice.

Vertex displacement-based discontinuous deformation analysis(DDA) was recently proposed to avoid the demerits caused by the original degree of freedom in DDA，but the current formulations developed by using the shape functions in polygonal finite element method have an unacceptable computational efficiency. To remedy this issue，a new formulation of DDA，utilizing VEM to define an individual displacement space and to calculate the potential energy for a block，and adopting original DDA to detect and analyze the contacts between blocks，is developed. The matrix expression for the block potential energy is mathematically deduced，and then the global equilibrium equations of the block system are derived based on the principle of minimum potential energy. A sliding block model is employed to determine the values of the multipliers in the approximations of the elastic deformation energy and the inertial force energy. The validity and computational efficiency of the new formulation are testified by three examples. Results show that the new formulation is capable to restrain the false volume expansion when simulating large rotation and to ensure the precision of the contact analysis. Most of all，the new formulation has a higher computational efficiency than the existing formulations of vertex displacement-based DDA.  

The crucial information acquisition and identification during the accumulation and evolution process of microfractures within rock can help to analyze the rock failure status，which is of great significance to the early warning and prevention of geotechnical disasters. In this paper，the granite failure experiments based on acoustic emission(AE) monitoring were conducted to analyze the stage characteristics of the energy frequency distribution and waveform spectrum variation during the failure processes，and to provide some suggestions with multiple AE parameters for evaluating the rock failure status，as well as to establish a discriminating method for crack propagation state in the plastic stage using integrated machine learning model. The research results show that the AE parameters including b value，S value，RA value，AF value，and average frequency of gravity(AFG) show obvious difference of change trend and temporal correlation in the four failure stages of compaction，elastic，steady propagation and unsteady propagation. The parameters characterize internal fracture evolution behavior from the viewpoints of damage degree，crack scale and source type，respectively. The continuous low-level decrease of b value，steady high-level fluctuation of S value，high-level decrease of AF value，low-level increase of RA value，and sudden decrease of AFG value correspond to the unstable cracking stage. The multiple AE precursor system and risk pre-alarm and evaluation criteria，which integrate the energy frequency distribution and waveform spectrum variation，overcome the defect of single index evaluation. Based on the analysis of above parameters，A(b) and main frequency bandwidth(W) are introduced to expand the datasets. Two types of crack identification models constructed by AdaBoost and Random Forest are used to identify the stable and unstable growth stages of rock cracks，with a classification accuracy of 94.0% and 95.1% respectively. The analysis method not only realizes the effective identification of rock failure stages at the laboratory scale，but also provides references for the early warning，prevention and control of disasters in practical engineering.

In order to simulate the operation process of gas mining first and then coal mining on site，the gas-containing coal thermal-fluid-solid coupling triaxial servo seepage device was used to conduct coal seepage tests under reduced pore pressure and full stress strain-seepage tests. By deriving the expression of the change in the width of coal cracks when the temperature rises，a coal permeability model considering temperature-stress coupling was constructed，and the evolution mechanism of coal gas seepage under the action of the temperature and the stress was discussed. The newly-built coal permeability model includes four influencing factors such as effective stress，adsorption/desorption，thermal expansion and thermal cracking，and uses damage variables to characterize the matrix expansion effect(thermal cracking) produced during the crack expansion process. The results show that，when the external stress is constant，the permeability first decreases slightly and then increases rapidly with decreasing the pore pressure at different temperatures，and when the pore pressure is constant，the permeability as a whole decreases first and then increases as the temperature increases. During the full stress strain-seepage test of coal，the permeability first decreases and then increases with increasing the axial stress，and both the elastic model and the peak intensity have a negative correlation with the temperature. The calculated values by the new permeability model are basically the same as the measured values，indicating that the model can better characterize the evolution of the permeability with the pore pressure and the effective stress. Based on the definition of the internal expansion stress，the contribution of the internal expansion deformation to the permeability during the action process of temperature and stress was explored. It is also shown that，when the temperature is constant，the permeability decreases with increasing the internal expansion factor，that the width and the damage of coal fractures are related and that the permeability decreases with increasing the temperature mutation coefficient.

In order to explore the classification method of asymmetrical large deformation of high stress layered soft rock tunnels，deformation data of 200 tunnels in soft rock are collected，and the major factors of asymmetrical deformation are analyzed. Relative deformation and asymmetrical deformation positions of the tunnels under high geo-stresses are investigated based on the association rule，and an improved classification method of asymmetrical squeezing deformation is put forward. The results show that the asymmetry factors are the inclination angle of the strata(a)，the angle between the rock strike and the tunnel axis(b )，and the angle between the maximum principal stress of the initial stress field and the rock plane(g ). 20 strong association rules，about the basic factor(compression stress and maximum principal stress) along with the relative deformation，and asymmetrical factor(a，b，g)corresponding to asymmetrical deformation position，are obtained. It is revealed that a，b and g together control the asymmetrical deformation position，which shifts from the sidewall and the bottom to the vault with increasing a，from the arch and the sidewall to the bottom with increasing b，and from the bottom to the sidewall and then to the vault with increasing g. The strength-stress ratio and the relative deformation determine the basic level of the squeezing，and the asymmetry factors a，b，g as sub-indexes identify the squeezing deformation position. The proposed method according to the level of the squeezing and the asymmetry factors provides an important approach for the asymmetrical large deformation classification of layered soft rock tunnels.  

Accurate landslide susceptibility evaluation is of great significance for disaster prevention and mitigation. In order to improve the accuracy of landslide susceptibility evaluation，based on geographic information system(GIS) platform，150 landslide disaster points in Zhenkang County were converted into raster data as evaluation samples，and 12 evaluation factors including elevation，gradient，slope direction，relief amplitude，topographic curvature，profile curvature，stratum，fault，annual rainfall，river，land use type and road were selected and passed the independence test to construct the evaluation index system of landslide susceptibility in the study area. Using GIS to randomly extract 70% of landslide rasters as training samples，the single evaluation model(normalized frequency ratio(NFR)，information(I)，certainty factor(CF)) and the coupled evaluation model (normalized frequency ratio-logistic regression(NFR-LR)，information-Logistic regression(I-LR)，certainty factor-logistic regression(CF-LR)) were adopted to evaluate landslide susceptibility. The frequency ratio of the remaining 30% landslides was analyzed. The AUC value is used to express the evaluation success rate and the prediction rate for accuracy testing. The results show that the frequency ratio of high and extremely high susceptibility is more than 86% of the totle and both the success rate and the prediction rate are greater than 0.75. Compared with the single model，the models with NFR，I and CF respectively coupled with LR have higher success rate and prediction rate，which shows that the coupled LR model has higher evaluation accuracy than the single model.

In order to remedy the deficiency of the conventional dynamic Winkler model in horizontal vibration analysis of single pile, a Timoshenko-Pasternak model is established based on the Pasternak foundation theory and Timoshenko beam theory，which considers both the shear effect of soil and the shear deformation of pile. Firstly，the differential transformation from the three-dimensional wave equation of soil is utilized to decouple soil equations，and separation variable method combined with continuity condition of pile-soil boundary is used solve the horizontal impedance of soil around pile. On this basis，the Timoshenko-Pasternak model is applied to derive the governing equation of horizontal vibration，and the analytical solution of dynamic complex impedance of the pile top in frequency domain is obtained by a transfer matrix method combining the boundary conditions at the pile bottom. The model is verified correct and reasonable by comparing with the existing model solutions. In addition，the pile characteristics and the properties of pile periphery soil are analyzed. The research results show that the vertical load can inhibit the impedance of the pile top. Meanwhile，the horizontal dynamic stiffness and the rocking stiffness of the pile top decrease gradually with increasing the vertical load. When the length of piles reaches the critical value of the aspect ratio(10–15)，the boundary conditions of the pile toe and the pile length have little effect on the impedance of the pile top. The impedance of the pile top would increase with decreasing the pile-soil elastic modulus ratio, and the influence of the elastic modulus of surface soil on the impedance of the pile top is much greater than that of undersoil.

It is relatively feasible to use PHC pipe pile composite foundation for constructing high embankments of more than 30 m in mountain basins and ravines with soft soil layers. The development and evolution characteristics of the soil arch of high embankments on soft ground strengthened with PHC pipe piles are studied through field tests. The results show that：(1) The distribution of the base pressure of the embankment affects the bearing mode of the foundation reinforced by PHC pipe piles. The uneven distribution of the base pressure will produce relatively large earth pressure between piles，which will lead to that the load of some parts is greater than the bearing capacity of the natural foundation. The pipe pile group can increase the bearing capacity of the soil layer between piles. (2) The compaction of the soil at the pile tip causes the stress relaxation of the pile top and increases the pressure on the soil between piles. Under high load，the phenomenon of pile tip penetration will occur，and the settling rate of the piles is higher than that of the soil between the piles. (3) The development and evolution characteristics of the soil arching in pipe pile composite foundation embankment are determined by load level and bearing stratum conditions. The penetration of the pile tip will lead to the temporary disappearance of the soil arch，which results in the local shear failure of soil between piles，aggravates the overall shear deformation of the foundation，makes the pile incline to form unstable soil arch and causes engineering safety hazards or accidents.

The second-order partial differential equation is used in the traditional calculation of soil consolidation. However，it is difficult to obtain analytical solutions in most cases for nonlinear consolidation problems. To solve this problem，a simplified analytical solution considering the nonlinear characteristics of soil is presented by reducing the order and introducing an equivalent coefficient that reflects the nonlinear characteristics of the soil.  The analytical solution can be expressed by elementary function，which can more conveniently calculate the degree of consolidation and the excess pore water pressure at each stage of soil. The error between the analytical solution and the differential numerical solution is less than 4.5% in the early consolidation stage，and the maximum deviation is about 10% in the late consolidation stage. Based on the analytical solution，it is easier to take other factors affecting consolidation into account，which provides a new way to deal with the consolidation problem.

The reef reclamation field survey results indicate that grain size distribution curves of coral sand in partial regions of coral ground layers，composed of coarse-grained and fine-grained particles in different proportions，are quite wide. Moreover，grasping the dynamic properties of coral sand in South China Sea where earthquakes frequently occur is significantly important for ground response analysis of reclamation reef islands. A series of resonant column tests were performed on coral sand-fines mixtures to investigate the influences of the density，the confining pressure and the fine content on their dynamic characteristics at small level strain in this study. The study employs the tamping energy method to prepare the coral sand-fine mixtures at different densities. The results indicate that the maximum dynamic shear modulus increases with increasing the density and the confining pressure. Under the same test condition，the maximum dynamic shear modulus decreases with increasing the amount of fines，due to that the presence of fines between coarse grains changes the contact condition between grains and the skeleton structure. The traditional expression of the void ratio has no capacity of describing the “real” compaction state of coral sand-fine mixtures and characterizing the role of fines in contributing the skeleton structure of sand. Based on the concept of the equivalent skeleton void ratio，an experienced model jointly considering the effects of the fine content，the density and the confining pressure is proposed to estimate the maximum dynamic modulus of coral sand-fine mixtures. This study is expected to provide a database for island reclamation site earthquake response analysis.