Clay rock is considered as an ideal medium for high-level radioactive waste geological repository due to its low permeability and self-sealing properties. The self-sealing properties of clay rocks can significantly reduce the permeability due to damage and hence prevent the radionuclide migration. The objective of this review is to discuss the state and development of the art in the self-sealing characteristics of clay rocks under coupled thermo-hydro-mechanical conditions from the aspects of experiment，mechanism and modeling investigations. The results show that the self-sealing characteristics of clay rocks are regulated by clay mineral content，stress state，water solution and temperature，etc. Based on the summary of advantages and disadvantages of the current experimental methods，a new transient approach is proposed to measure the permeability variation of clay rocks during the self-sealing process. The focuses of future researches，such as micro-mechanisms of self-sealing，self-sealing characteristics under coupled thermo-hydro-mechanical-chemical conditions，effects of creep development on self-sealing and self-sealing model establishment considering the evolution of permeability within excavation damage zones，are discussed.

In order to explore the dynamic mechanical properties of layered composite rocks which are common in rock engineering，layered composite rock samples spliced by red and gray sandstones were prepared. Impact compression tests in two cases of gray sandstone and red sandstone near the incident bar at different impact velocities were carried out using split Hopkinson pressure bar(SHPB) test system，and the stress wave propagation characteristics，dynamic stress-strain relationship and energy dissipation law of composite rock mass in two cases were studied and compared. The stress characteristics and strength conditions of composite rock mass were analyzed theoretically，and the failure characteristics of composite rock mass were studied by using ultra-high speed digital image correlation(DIC) test system. The results show that the dynamic mechanical properties and energy dissipation laws of composite rock mass have obvious strain rate effect. At the same impact velocity， the dynamic characteristics of composite rock mass in the case of the stress wave propagating from the hard to the soft are obviously different from those in the case of the stress wave propagating from the soft to the hard due to the matching relationship of the wave impedance. However，the difference gradually decreases and tends to be zero with increasing the impact velocity. It is also shown that the failure degree and failure form of the two parts of composite rock are obviously different. The damage degree of the red sandstone with relatively small wave impedance is more severe than that of the gray sandstone. The red sandstone mainly shows shear failure，and the failure of the part at the boundary layer legs other regions. For the gray sandstone，tensile failure is dominant and local shear failure occurs at a high impact velocity，and the part at the boundary layer fails earlier than other regions.

Aiming at the condition of high horizontal stress difference in deep shale(greater than 10 MPa)，in order to clarify the formation law of complex fracture network in deep shale layers and to explore the stimulation methods to improve the complexity of fracture network，three fracturing modes were designed including gradually increasing the pumping rate in a pulsed style，step-form increasing the pumping rate and maintaining a constant pumping rate. By means of a large hydraulic fracturing apparatus under true triaxial condition，acoustic emission monitoring system and dissection photos of samples，the crack modes and extension rules of hydraulic fractures in deep shale were analyzed. The experimental results show that to some extent the total volume of injected fracturing fluid can reflect the complexity of fractures，and the more the total volume，the more complex the fracture net. For the fracturing mode with a pulsed pumping rate，the pump-stopping period contributes to the infiltration of the fracturing fluid into natural cracks and hence to activate natural fractures. The pumping rate of the fracturing fluid has a great impact on the formation of the complex fracture network，and a small pumping rate is conducive to the opening of original natural fractures while a high pumping rate makes the hydraulic fracture directly cut cross the pre-existing natural fractures. It is very important to open the natural fractures which are the material basis for forming the complex fracture net. The experimental study can provide a reference for on-site fracturing design.

In order to obtain the variation law of wave velocities of deep rocks under certain confining pressure and continuous loading condition，the triaxial compression tests of granite under confining pressure levels of 40 MPa and 80 MPa were carried out by GCTS RTX–3000 rock mechanics testing system，and the stress-strain curve as well as compression and shear wave velocities was obtained. The results show that the compression and shear wave velocities of granite increase with increasing the confining pressure in a quadratic form. During the triaxial loading process，the compression and shear wave velocities increase sharply and then tend to be stable，while in the process from crack initiation to failure，the wave velocities slowly decrease and then drop sharply. The shear wave is more sensitive to the stress state of the confining pressure and the loading process. The damage analysis of the rock in the whole loading process was carried out and it is shown that，at different stages，the dynamic elastic modulus shows an increasing，stable or decreasing trend，and that the dynamic Poisson?s ratio reflects the expansion process of the rock. The study is helpful to understand the damage characteristics of rock mass under high confining pressure conditions and of great significance for the study of deep surrounding rock control，earthquake prediction and so on.

The displacement and stress state of high arch dams are the key concerns of arch dams during the initial impoundment period. In this paper，adopting the microseismic monitoring technology in combination of finite element numerical simulation，the internal correlation between microseismic deformation and stress in arch dam was studied，and the change laws of stress and displacement during the initial impoundment period were analyzed. The evolution law of working behavior during the initial impoundment period was investigated，and a method for judging the actual stress state of the arch dam by microseismic events was proposed. The results show that the microseismic events are consistent with the stress distribution of the arch dam in space and time and that the concentration and migration of the high compressive stress of the arch dam are the internal driving force of microseismic events. Both the high compressive stress and the microseismic deformation are concentrated on the dam heel before impoundment while transferred from the dam heel to the dam toe after impoundment. It is also revealed that the principle tensile stress zone is transferred from the arch dam abutment to the dam heel after impoundment. The distribution of the stress concentration area of the arch dam in different impoundment periods can be inferred from the cumulative frequency distribution of   of microseismic events. The results can provide a certain reference for the study on actual working performances of arch dams.

After the impoundment of 175 m above the sea level of the Three Gorges Reservoir，several geo-hazards happened in gorge areas，resulting in wide attention to the deterioration of rock mass in the water level fluctuation zone of karst bank slopes. Based on field investigations as well as in-situ and laboratory tests，the deterioration characteristics of shallow rock mass in the zone were systematically summarized for the first time in this paper. From the perspective of macro-deterioration phenomena of rock mass including dissolution，crack manifestation and propagation，and mechanical erosion，the macro-deterioration performance of karst rock masses with different structures is very different. The mechanical parameters of limestone samples averagely decrease by about 0.7% after an immersion-air drying cycle，and the strength of the samples decreases with rising the number of cycles in an exponential function with a correlation coefficient larger than 0.84. The annual decline rate of the acoustic wave in fractured limestone of Jianchuandong is 11.23%. Borehole multi-period acoustic penetration test results show that the deterioration of underground karst rock mass is mainly deterioration of structure planes and the annual decline rate is about 10%–60%. These works show the unique deterioration characteristics of shallow karst rock mass such as a low deterioration rate of rock accompanied with a high deterioration rate of structural planes，non-uniformity，and zonation of the deterioration rate according to the weathering or fracture zones of rock mass. Based on these characteristics，two deterioration models of rock mass respectively corresponding to equivalent continuous mode and structural plane mode were established. This research points out the future research focus of deterioration properties of rock mass in reservoirs and provides an important support for the prevention and mitigation of potential geological hazards in the water level fluctuation zone in Three Gorges Reservoir area.

Unique climatic characteristics and complex hydrochemical environments lead to freeze-thaw and chemical dissolution combining action，which is an important reason for the exfoliating and nick becoming shallow of the metamorphic sandstone carrier of the Helankou rock paintings. The mass，elastic wave velocity and uniaxial compressive strength of rock samples after 0，15，30，45 and 60 freeze-thaw cycles respectively immersed in distilled water and Na2SO4，NaHCO3 or CaCl2 solution of 0.5 mol/L concentration were tested，and the damage characteristics of rock paintings carrier under the combined action of chemical and freeze-thaw were systematically explored. The cumulative damage mechanism was analyzed qualitatively and quantitatively by scanning electron microscopy(SEM)，X-ray diffraction analysis(XRD) and the damage variable based on the change of the porosity. The results show that the rock samples present different degrees of cumulative damage in the process of freezing and thawing cycles under different conditions and that the damage is caused by the differences of the type，quantity and connection of the sample pore aroused by different combinations of frost heave，dissolution and salt crystallization.

Taking the steeply inclined seam mining as the research background and using the methods of engineering practice summary，theoretical analysis，mechanical modeling and physical similar model test，the failure law of the roof in steeply inclined seam mining was analyzed adopting BOTDA(distributed optical fiber sensing based on Brillouin scattering principle) and DIC(three-dimensional optical digital speckle) technologies. The research results show that the initial stress in the steeply inclined seam obeys a distribution of the largest in the middle part，the second in the lower part and the smallest in the upper part，that the bending moment and shear force in the middle-upper part are larger than those in the lower part，that the density of gangue accumulation gradually decreases from the bottom to the top，and that the activity of the upper and middle roof is intense while the lower part is relatively stable. Once the strain detected by optical fiber which can sense the internal weak deformation of rock mass，develops from monotonous increasing to decreasing，the roof will collapse，and at this moment，the instantaneous strain reaches the maximum. Both BOTDA and DIC techniques can detect the development and closure process of the roof abscission layer. The former shows a step change of the strain value and the later presents a strain mutation zone formed at the abscission layer. The monitoring results of the displacement at the same position by both total station and DIC reveal that the internal strain of the upper and middle basic roof is much larger than that of the lower part，which shows that the overburden deformation in steeply inclined seam mining is asymmetric. The research results in this paper can be used for reference in monitoring deformation and failure of geotechnical structures by using optical fiber sensing and DIC techniques.

In order to study the gas tightness characteristics of gypsum rock as cap rock in energy storage in the deep rock environment，the modified THM coupling triaxial rock permeability test platform based on the MTS 815 rock mechanics test system of Sichuan University was used to perform gas permeability tests of gypsum rock under different temperatures and confining pressures for the first time in China. The test results show that the gypsum rock in the natural state with a permeability ranging between 10－17–10－15 m2 can be classified to the dense low permeability rock medium. At the same temperature，the stress-strain curve of the gypsum rock has a brittle-ductile transition characteristic with increasing the confining pressure，and at the same time the peak stress of the gypsum rock increases continuously. Under the same confining pressure，with increasing the temperature，gypsum samples show thermal damage and thermal softening effects，in other words，the peak stress reduces gradually and the plastic deformation ability increases. The initial permeability of the gypsum rock decreases in an exponential function with increasing the confining pressure. The initial permeability of the gypsum rock under the confining pressure of 5 MPa is 4.13×10－17 m2，while under the confining pressure of 15，25 and 35 MPa，the initial permeability decreases by 37.23%，65.86% and 75.79%，respectively. Under different temperature- mechanics coupling conditions，the permeability of the gypsum rock shows a similar decrease-increase trend，and the overall permeability level of the rock decreases with increasing the temperature or the confining pressure.

Prediction of the stope weighting intensity is an important part of mine pressure disaster prevention and control and a main basis of strata control. A strata strength index was defined and a new method for classification forecasting of strata behaviors of thick coal seams with hard roofs was put forward. According to the mining practice in Datong mining area，a classification and prediction index system of strata behaviors of thick seams with hard roofs was established by taking the instability condition of far-field high-level structure as the core and taking into account the basic indexes and strengthening conditions that affect the strata behaviors. Based on the fuzzy mathematics theory，a classification forecasting model of the strata behaviors was established，and four different levels of quantitative indexes for different factors were given. The proposed method was applied to predict the weighting strength of 8105 working face of the extra-thick coal seam with a hard roof in Tongxin coal mine. It is shown that the predicted result is in good agreement with the mining practice and that the method can accurately predict strata behaviors in hard roof thick coal seams. The index system of the classification and prediction method of the weighting strength index is universal，comprehensive and systematic，and the classification of index parameters is detailed and operable. The proposed method can provide theoretical reference for the prediction of the stope weighting intensity and the management of roofs of thick seams with hard roofs in other mining areas.

The calculation of the surrounding rock pressure of shield tunnels in compound strata is still controversial currently. Aiming at the problems of the calculation of the surrounding rock pressure in compound strata by the classic modified routine method，load calculation models of shield tunnels for two cases of the upper-soft and lower-hard mixed soil ground and the upper-soil and lower-rock mixed ground were proposed，and a formula for calculating the active earth pressure in the lower part of the mixed soil ground was derived based on the slip-line theory. Comparisons were conducted among the results of the proposed method，the modified routine method and in-situ tests against the above two kinds of typical compound strata. The results show that the passive reaction acting on the bottom of tunnels is exaggerated by the modified routine method，which leads to unrealistic surrounding rock pressure，upward deformation and greatly different internal force compared with the measured results at bottom. However，the calculation results of the surrounding rock pressure，tunnel deformation as well as the distribution and the value of the internal force by the proposed method in this paper are in good agreement with the in-situ test results. The proposed method can provide reference for the design and research of shield tunnels in compound strata.

Granite is a candidate wall rock for high-level radioactive waste repository in China. The development of multi-scale discontinuities has a key impact on the closure of the repository. Taking grades II，III，IV-V discontinuities of Shazaoyuan granite masses in Beishan as the research objects，the trace length and occurrence parameters of multi-scale discontinuities were obtained based on the literature investigation and field measurement. The trace length distribution of multi-scale discontinuities was analyzed by mathematical statistics. Compared with the exponential distribution，the power law distribution is more applicable to the trace length of multi-scale discontinuities，showing scale-independent scaling uniformity with a scale of 2.236. Adopting the K-means algorithm based on particle swarm optimization，the dominant attitude of multi-scale discontinuities was identified. The dominant trend and dip angle of grades II，III and IV-V discontinuities are，respectively，NW320°and 56°–76°，NW304°–314°or NE43.5° and 71.3°–72.9°or 82.3°，and NE38.8°–41.5° and 70.0°–70.9°，showing a scale-dependent difference. Based on the“ladder”formation mechanism of discontinuities and the model of secondary discontinuities generated by strike-slip strain，a“ladder-shear”model was proposed to explain the combination morphological reasons of multi-scale discontinuities and to establish the genetic relationship of multi-scale discontinuities in Shazaoyuan granite.

Taking the deep mining roadway in Jisan coal mine as the research object，the deformation and failure mechanisms of surrounding rock，and the principle and application effect of anti-scouring and releasing energy coupling support technology were studied by combining theoretical analysis，numerical simulation and laboratory test to solve the problems of large deformation of the surrounding rock and easy failure of the support body in deep mining roadway. The results show that large deformation and impact of deep mining roadway in Jisan mining area own to the complex high stress field and its superposition，which make the roof of thick hard sandstone easily accumulate energy. Comparing with the traditional support system which cannot effectively absorb and transform the residual energy of the surrounding rock，the constant resistance large deformation support system can absorb more energy(DF?x) and realize the controlled release of the shape energy of the surrounding rock due to that the constant resistance value(F) and the deformation quantity( ) can be designed independently，which solves the problems of high prestressing force difficult to apply，easy to break and quantitative anti-scour design in the anti-scour support system. The field application results show that the deformation and the advance influence range of the surrounding rock of the constant resistance support are respectively reduced by about 40% and 33% compared with the original support. The research results can provide a reference for similar deep mining roadway support design with an impact tendency.

An improved ubiquitous-joint constitutive model(Transverse Isotropic Elasto-Plastic Ubiquitous-Joint model)，which can take into account both the strength anisotropy and the deformation anisotropy of phyllite，was developed in FLAC3D，and a formula for analyzing elastic deformation anisotropy of transversely isotropic materials was derived. Furthermore，the excavation of the tunnel with steeply dipping phyllite strata was simulated，the corresponding destruction mechanism was revealed and the validity of this model was verified. The results reveal that the tunnel surrounding rock is very prone to shear failure along the weak plane due to the low shear strength of the weak plane and that the tunnel surrounding rock of the tunnel outline parallel to the weak plane is prone to tension failure at which the tunnel outline is parallel to the weak plane because of the low tensile strength of the weak plane. The concentration of the compressive stress can lead to the shear failure of the rock matrix while the tensile failure of the rock matrix does not occur in the process of tunnel excavation. Under the influence of deformation anisotropy of phyllite，the displacement field of the surrounding rock shows obvious asymmetry. A larger ratio of the horizontal stress to the vertical stress will result in compression deformation of the surrounding rock towards the tunnel，which is the main reason for the failure of the supporting structure. The research results in the paper can provide a useful reference for similar projects.

鉴于目前工程中含多目标变量多参数输出的概率反分析方法匮乏，在改进多输出支持向量机算法(MSVM)的基础上，建立基于贝叶斯理论(Bayes)的概率反分析方法(B-MSVM方法)。该方法通过改进支持向量机算法形成多个岩体参数与多目标变量之间的映射关系，以分步开挖引起的典型测点的松弛深度和表层变形监测信息为输入，以边坡岩体多个力学参数为待反分析输出，通过选择合适的核函数在改进的支持向量机算法中运算，获得多次开挖条件下待反分析参数的取值及其不确定性动态表征。应用该方法对白鹤滩水电站坝基边坡的力学参数进行反分析，得到10个非相关参数的取值及其不确定性分布，用反分析的参数值计算相应开挖步下边坡典型测点的位移和松弛深度，并与实测值进行对比，结果表明该方法的正确性，并初步讨论本方法在相关参数反分析计算中的应用思路。研究成果为岩土工程参数概率反分析方法的建立提供了思路，具有重要的理论意义和工程实用价值。

Based on several typical high dams in China，the grading characteristics of rockfill and gravel were analyzed，and soil grade reasonable scale method of the super-diameter coarse particles was studied combined with the indoor relative density test and large compression test of Dashixia and Changheba dam materials. The results show that Weibull model can well reflect the gradation and fractal characteristics of dam coarse-grained soils and that common scale methods such as knockout method，equal replacement method and similar grading method can be expressed by a unified grading scale formula to accurately calculate the scale test gradation based on Weibull grading model. Using the critical P5 value corresponding to the optimal particle filling relationship as the condition of the similar scale method instead of less than 5 mm particle mass percentage P5 not more than 15% recommended by codes，the scale test error due to excessive use of the mixing method can be avoided and the scale grading“sanding”problem can also be eliminated. At the same time，the geometric similarity of the grading can be ensured and the accuracy of the scale test results can be improved effectively. For the super-diameter coarse-grained soil with different distribution types，based on the property of the critical fractal dimension Dc independent of the maximum particle size，the critical P5 value can be calculated by the fractal grading formula and the corresponding grading scale method can be directly selected according to the parameters of the original graded soil. The research results can be used for the scale test of super-diameter coarse-grained soil and have strong application value.

Based on the characteristics of saturated structural clays and the uniform hardening(UH)parameter，the UH model was modified to reflect the stress-strain relationship of the structural clay. The improved model has the following features：(1) the yield surface being shifted to the left in the p-q coordinate system can reflect certain tensile strength characteristics and，because of that the left end of the yield surface is located to the left of the origin point，the loss law of the cementation strength caused by the development of the volume strain can be described by a proposed evolution equation of left movement of the yield surface，(2) by introducing the state parameter χ to describe the variation of the strength of the phase transformation stress ratio corresponding to the moment when the volume strain changes from shrinkage to dilatation，the volume strain amount and the transformation rule can be determined according with different cementation degrees，and (3) for the characteristics of large volume shear contraction of structural clays under loading，a structural stress ratio parameter R* and  a formula of the structural potential strength based on R* were proposed. By using the potential strength to revise UH parameter，a simple model for describing the stress-strain relationship of structural clays was obtained，which reflects the following characteristics including the high stress ratio strength，gradual decrease of the cementation strength along with the volume contraction，large volume shear shrinkage，strain softening accompanied by cementation loss，shear shrinkage and dilatancy.

In order to investigate the dynamic behaviors and influence factors of saturated loess，a series of dynamic triaxial tests were conducted to analyze the dynamic shear modulus and damping ratio of the loess sampled from 11 different sites in Loess Plateau，and the dynamic shear modulus ratio and the damping ratio were obtained by fitting the test results. The regional differences of the dynamic shear modulus ratio and damping ratio of saturated loess were discussed，and the differences of the dynamic shear modulus ratio and the damping ratio between the saturated loess and the original loess were also analyzed. In addition，influence of physical indexes on fitting parameters of the dynamic modulus and the damping ratio of the saturated loess was analyzed. The results indicate that the dynamic constitutive relation of the saturated loess obeys the Hardin-Drnevich model. The regional distributive characteristics of the loess have a significant influence on the damping ratio while slight on the dynamic shear modulus ratio. Both the value and the regional discreteness of the dynamic shear modulus ratio of the saturated loess are much smaller than those of the original loess. In the same site，however，the damping ratio of the saturated loess is markedly larger than that of the original loess，which is influenced by the loess structure. The maximum dynamic shear modulus of the saturated loess is greatly influenced by the initial void ratio，and the changes of the ultimate dynamic shear stress amplitude and the maximum damping ratio are mainly caused by the variation of structural characteristics of the loess resulted from the increase of the clay content.

In the existing researches of ground surface deformation caused by shield construction，soil is regarded as a linear elastic material and elastic theory is adopted to predict ground settlement，which may lead to inaccuracy. In this paper，the stability of upper soil under the loading-unloading condition during and after shield tunneling was analyzed by introducing the combined strength theory，and the triaxial consolidation undrained test was carried out by simulating the stress path of the soil during and after shield tunneling. Based on the stress-strain hyperbola relationship obtained from the test data，a formula of the nonlinear tangent elastic modulus of the upper soil under vertical loading and unloading conditions was derived and the parameters were determined. The results show that，under the same confining pressure or the same consolidation stress ratio，the strength of soil under loading path is greater than that under unloading path，and that，under the same confining pressure，the principal stress of soil at failure increases with increasing the consolidation stress ratio under axial loading or unloading. For predicting surface deformation，the axial strain data are used for the stress path method，and the nonlinear tangent modulus and test parameters of loading and unloading are adopted for the elastic theory method. Taking the Jiangnan shield section of Wuhan River-crossing Tunnel as an example，the predicted heave values calculated by the stress path method and the elasticity theory method differ by 4.2% and the difference between the predicted settlement values obtained by the two methods is 13.0%. It is also revealed that the predicted heave values differ the measurements by 7.5% and 10.7% respectively，and that the predicted settlement values are consistent with the measurements of the total settlement.

It is difficult to accurately evaluate the collapsible deformation of the deep loess strata under loess tunnels by using laboratory compression test or field pit immersion test. In this paper，it is proposed to carry out sand well immersion test to measure and evaluate the collapsibility of loess tunnel foundations. Comparisons among the results of sand well immersion test，field pit immersion test and laboratory test were performed，and the reasonability and reliability of sand well immersion test used to evaluate the collapsible deformation of loess tunnel foundations were demonstrated. The results indicate that the collapsible deformation of soil columns around the sand wall could be effectively released under the immersion condition of the sand well test，and that the deeper the sand well is buried，the more the collapsible deformation of the strata under the bottom of the well develops completely，which shows that the sand well immersion test is more applicable for measuring the collapsible deformation of loess strata with a large buried depth. The sand well immersion test can better simulate the hydraulic condition of collapse deformation of the strata under the tunnel foundations，and the test method can be applied conveniently along the tunnel in loess plateau region due to low requirement of site conditions，less water，short cycle and low cost. Finally，some improvements were put forward to solve the defects of sand well immersion test at present.