To explore the relationship between the ejection velocity of unidirectional double-face rockburst fragments and the bedding dip angle()，seven groups of unidirectional double-face unloading rockburst experiments of sandstone with different  were carried out by using a self-developed true triaxial rockburst experimental system，and the ejection velocity of double-face unloading rockburst in sandstone with differentwas analyzed by particle image velocimetry(PIV). The results show that the rockburst phenomenon and duration of the two free surfaces are not all the same，and that the average velocity change process of the two free surfaces can be divided into four stages：particle ejection or fragment stripping，fragment block breaking，fragment ejection and late ejection. In the process of double-face unloading rockburst，both the average maximum velocity and the maximum initial velocity of the two free surfaces change with  in a concave parabola form，reaching the minimum and maximum values at 60° and 0° of  respectively. The change processes of the peak stress and the maximum principal stress decreasing rate at the time of rockburst withalso show an upward concave parabola. In terms of the difficulty degree of rockburst，when is 60°，the rockburst is easy to happen but the corresponding rockburst intensity is the weakest. The horizontal bedding is the least prone to rockburst，while the rockburst is strong once it occurs. The difference of the rockburst intensity of sandstone with differentis affected by the brittleness and the peak stress of rockburst.

Experimental study in deep rock dynamics is an important but challenging direction for deep underground rock engineering. Recently，great advances have been made by researchers in the experimental studies of deep rock dynamic properties using the split Hopkinson pressure bar(SHPB) with confinement. It is thus imperative to systematically review the progress in this direction. This paper mainly focuses on the experimental study of deep rock dynamics using SHPB with confinement，including new advances in experimental apparatuses，methodologies and results. First of all，a comprehensive introduction to the working principles of the spilt Hopkinson pressure bar and the momentum-trap technique is given. Secondly，the development of SHPB with confinement utilized for conducting deep rock dynamics tests is briefly presented. Moreover，the experimental methods for determining dynamic compressive，tensile，bending and shear strengths of rock under confinement including axial，hydrostatic and triaxial pressures are systematically discussed，and the corresponding dynamical responses of rock in these tests are also revealed. The rate-dependence characteristics of dynamic strengths for deep rock are summarized and the mechanisms are then discussed. Besides，the experimental methods and results for quantifying the dynamic Mode I and Mode II fracture toughness are also presented.

Quantitatively characterizing joint roughness is of great significance to accurately understand joint mechanical properties. As indicated in the literature，the root mean square(Z2) and the structure function(SF) among many statistical parameters for joint roughness have the best correlation with JRC. However，the sampling interval(SI) is an important obstacle restricting their practical application. In this paper，30 sets of Z2 and SF values of ten joint profiles from Barton¢s literature with SI ranging in [0.2 mm，10 mm] were calculated using digital image processing technology. The influence of SI on Z2 and SF was discussed，and the relationships between the combination parameters (Z2，SI) and (SF，SI) with JRC were analyzed. Consequently，a method for evaluating the joint surface roughness JRC by the combined parameters(Z2，SI) and (SF，SI) with SI belonging to [1 mm，10 mm] was proposed，and the reliability of the proposed formulas was verified by shear tests. The results show that，for the same joint profile，with increasing SI，Z2 decreases gradually while SF increases，and that both Z2 and SF have a good power function relation with SI and the coefficients of the power functions rise with increasing JCR. The calculation roughness of Barton curves by the two formulas shows that the estimation values of three joint profiles of JRC0–2，JRC16–18 and JRC18–20 are slightly smaller on the whole，the estimation values of JRC4–6 and JRC10–12 are slightly larger，and the values of the other five joint profiles are basically distributed within the respective range. Comparison between the roughness of the test structural surface along four directions by the direct shear test and the results calculated by the developed formulas shows that the roughness estimation values are in agreement with the test values on the whole. When the maximum allowable deviation is set as 4，the accuracy of the roughness of the structural surface along four directions evaluated by the combination parameters (Z2，SI) and (SF，SI) with random interval is not less than 83.33%. This research provides a new way for evaluating structural surface roughness with statistical parameters.

The difficulties of complex landslide control lie in the determination of stability and the identification of key control parts. Taking a linear complex landslide as an example，in this paper，the method for determining the stability state and the identification of key control parts of the landslide are studied from the perspective of progressive failure process. First of all，aiming at the generalized geological structure model of the landslide，a progressive failure mechanical model is established based on the strain-softening theory. Subsequently，a five-stage division model of the progressive failure process is proposed，and the stability state equations of the landslide are constructed for each stage based on the static balance principle. The mechanical model and stability state equations reflect the changing laws of equivalent load，stress distribution，deformation characteristics and stability during the evolution of this type of landslide，and reveal the progressive failure characteristics of the landslide，involving softening from both ends to the middle and losing stability from the local to the whole. Based on this，the stability state of the landslide can be effectively determined. A case study shows that the attenuation amplitude of the landslide stability increases with the development of progressive failure. If the lengths of the two destruction zones are different，the attenuation rate of the stability of the shorter zone is greater than that of the longer zone. In addition，when the sliding bands at both ends start to shear，the equivalent load of the longer zone is greater than that of the shorter zone，showing that the shorter zone is the key control part of this type of landslide. The research has certain theoretical significance and application value.

The in-situ survey and identification of geometric properties of rock discontinuities in jointed rock mass is one of the basic tasks for the stability analysis of rock engineering. In order to solve the problems of the traditional discontinuity survey methods when obtaining the structural plane information，such as low efficiency，high risk，high subjectivity and data sharing difficulty，An automatic identification algorithm of rock mass structural planes，considering three sensitivity parameters including the number of neighbor points k，the angle threshold j and the filter factor f，was proposed based on the three-dimensional point cloud data of rock mass surfaces using MATLAB code. Based on the neighborhood point searching method，the normal vector analysis of the neighborhood point plane was firstly carried out. Then，the coordinate information of the normal vector point set belonging to the same group of structural planes was determined according to the threshold j，and the coplanar point cloud was reproduced in the same color display mode. The optimal groups of structural planes were discussed based on the influence of the filter factor f on varied types of point clouds. Finally，the fast identification and recognition of dip direction and dip angle of dominant discontinuties，occurrence projection and rose diagram were achieved. The research results can provide one reliable application method for the intelligent and efficient measurement of in-site rock discontinuities.

During the preliminary excavation of the main power house of Shuangjiangkou hydropower station，the brittle failure phenomenon is obvious，and the surrounding rock deformation of the area affected by porphyry veins is prominent. To this end，after the preliminary excavation of the main powerhouse，a comprehensive analysis is conducted on deformation and cracking behaviors of surrounding rock and stability of the cavern，which consists of monitoring of surrounding rock deformation by multi-point displacement meters，imaging observation of surrounding rock fractures by borehole camera，numerical simulation of excavation process and effects on local site deformation of the porphyry vein based on 3DEC software. A novel method for evaluating the stability of caverns based on the surrounding rock loosening zone and the cross-sectional area of the cavern is proposed. The results show that，after the first floor excavation，the deformation of the surrounding rock of the main power house is small as a whole，but the top arch sinks relatively largely. The time-dependent deformation characteristics of the hard granite surrounding rock are not obvious. The surrounding rock deformation is mainly affected by the excavation driving face，and the control range of the excavation face to the deformation of the cave segment affected by the porphyry veins is about 1.5 times the cave span. In addition，there are cracks in the shallow and deep parts of the surrounding rock after excavation，and the cracking phenomenon at the junction of the veins and homogeneous rock is serious. Excavation unloading causes the slip of the upper plate of the porphyry veins，which results in shear deformation of the top arch of the cavern. It is very effective to add anchor cables that completely penetrates the porphyry veins，which significantly improves the stability of the relevant tunnel sections. The research results will provide an important basis for both the optimization of the subsequent excavation and support scheme of the hydropower station and the selection of reinforcement measures for local instability.

Fractured rock mass statistical homogeneous area division is the basis for evaluating quality and stability of rock mass and modeling. The rock mass homogenous area division methods based on Miller method are limited by sample size，degree of freedom and Lancaster rules. In this paper，Miller method was optimized from three levels including block network division scheme，overall significance level value and principle of merging blank areas. Some typical outcrops in the preselected site of a nuclear waste repository in Beishan，Gansu province，were selected as the research objects，and the rock mass statistical homogeneous area was comprehensively analyzed and evaluated combined with the Mathab method and the Pearson correlation coefficient method. The results show that the optimized Miller method is more adaptable than the original method for the coexistence of steep and gentle dips in the Beishan area，that the division results of the Mathab method fluctuate greatly and have lower credibility，and that Pearson¢s correlation coefficient method is not strong in identifying correlation in statistical significance. The improved Miller method is more applicable to the division of fractured rock mass homogeneous area under complex conditions.

The freeze-thaw cycle is one of the main reasons affecting the weathering of Maijishan grottoes. The changes of the wave velocity、the mass and the tensile strength of the saturated sandy conglomerate under open conditions due to freeze-thaw cycles are studied through laboratory experiments in 3 temperature ranges of  －5 ℃–20 ℃，－10 ℃–20 ℃ and －15 ℃–20 ℃，and CT and digital image processing techniques are used to analyze the changes of the microstructure characteristics of the rock samples. The concept of homogenized stress is introduced and compared with the macromechanical properties of the rock as a criterion for whether the rock is damaged. The results show that the mass，the wave velocity and the tensile strength are inversely proportional to the number of freeze-thaw cycles but directly proportional to the minimum temperature of the freeze-thaw cycle. It is proposed that the temperature range is the key environmental control factor for the freeze-thaw degradation of rock，and the destruction of the original cement structure of the rock and the pores are the key internal factor. The comparison between the crystallization homogenization stress and the rock yield strength can be better used to judge the influence of freezing and thawing on rock damage. The research results are expected to provide a theory for the research and development of freeze-thaw weathering mechanisms of stone cultural relics and related protection technologies.

A large-scale three-dimensional model test system concerning rockburst disaster evolution and instability mechanism simulation，applying hydraulic loading and explosive blasting to respectively simulate in-situ stress field and dynamic load，was developed independently to investigate the impact instability process of deep roadway under the combined action of dynamic and static loads. In the whole testing process，the stress field，deformation field and geoelectric field will be obtained by using the multiple monitoring means such as parallel electrical network method，static strain acquisition system，ultra-dynamic strain acquisition system，high-speed camera and acceleration sensor. The test results show that，during the process of stress redistribution，the stress level of the surrounding rock in the shallow region of the roadway deteriorates seriously，forming a certain range of high resistance areas，while the tangential stress in the deep region of the surrounding rock appears a gradually increase trend，forming a lower resistance area. All above observations indicate that the state of the shallow surrounding rock switches from elastic to plastic，while that there is a large amount of elastic energy accumulation in the deep region，which provides favorable conditions for the occurrence of rock burst. At the moment of applying the dynamic load，the superposed force of the impact dynamic load and the high static load increases sharply and exceeds the bearing capacity of the surrounding rock，causing the broken rock mass in the shallow region of the roof to be thrown into the excavation space instantaneously accompanied by the rapid release of the elastic energy accumulated in the deep region of the surrounding rock. A large number of tensile and shear cracks are observed on the two sides of the roadway and the floor，which can be attributed to the repeated action of shock stress waves. It is shown that the test system is stable and reliable and can reproduce the process of impact instability of deep roadways realistically. The research work provides a guide for performing the failure tests of roadways with different support structures under dynamic and static loads.

To explore the influence of the joint angle on the dynamic responses of rocks under one-dimensional dynamic load，the split Hopkinson pressure bar(SHPB) was used to carry out impact tests on prefabricated complete specimens and 7 groups of cement mortar specimens with different joint angles. Before and after the tests，nuclear magnetic resonance(NMR) imaging system was used to detect the porosity and pore size distribution of the samples. The influence of the joint angle on the dynamic response characteristics of rock-like materials was systematically analyzed from the aspects of dynamic strength，energy dissipation and meso-damage. The results show that the peak strength of the specimens first decreases and then increases when the joint angle increases from 0° to 90°. The specimens with a joint angle ranging between 45° and 60°are more likely to be damaged than those with other joint angles. The damage of the specimens is positively related to energy absorption. Both the porosity rate and the energy absorption of the specimens present an inverted “U” shape with the joint angle. The specimens with a joint angle ranging from 45° to 60° absorb the most energy，and the change rate of the porosity before and after impact is the most significant. It is concluded that the angle between the directions of the load and the joint，most conducive to crushing，is 30°–45°.

Relying on the engineering background of Zangga tunnel in Lalin section of the Sichuan—Tibet railway，a coarse-grained simulation method considering the shape feature of blocks is built up by using digital image method and discrete element method based on the engineering geological characteristics of the glacial deposits. The failure characteristics and meso-mechanisms of the surrounding rock caused by tunnel excavation are discussed through numerical simulation，and the pre-reinforcement measures of the surrounding rock are proposed. The research shows that the surrounding rock of the glacial deposit tunnel performs a progressive failure model along the whole ring，presenting a dynamic cycle process from initial loosening zone formation，shear fracture surface development，loose zone expansion to shear fracture surface extension. The degradation of particle contact in the loosening zone proves the development of shear fractures in soils. In addition，the evolution of the structural characteristics of the force chain reveals that the structure of the force chain degenerates from a ring shape to a chain shape，which ultimately leads to the failure of the block stone skeleton and the loosening of the surrounding rock. Engineering application results show that，the proposed pre-reinforcement measures of curtain grouting + advanced piperoof + small ducts can significantly inhibit the development of the fractures in surrounding rock and effectively control the excavation stability in the glacial deposit tunnels. Both drilling core and tunnel deformation monitoring results meet engineering requirements.

To investigate the three-dimensional earth pressure distribution and deformation characteristics of piled embankments with retaining wall，ten groups of model tests considering the embankment height，the clear distance between piles as well as even and uneven settlements of soil between piles were carried out using a multiple trapdoor test setup. The displacement of sand fill was measured adopting particle image velocimetry technique (PIV)，and the soil pressures between the piles，on the pile top and on the retaining wall were monitored by self-made load gauges and earth pressure cells. The test results show that the embankment has two deformation patterns including triangle expanding pattern and tower-shape development pattern. With increasing the embankment height，the minimum and residual values of the stress reduction ratio decrease，while the retrogression rate(stress recovering rate) of the soil arching effect and the settlement for the residual stage increase. The uneven settlement weakens the peak soil arching effect but has little influence on the residual value of the soil arching effect. The soil arching effect in the embankment fill induces the concentration of the earth pressures at the pile top and a certain height in the central part of the embankment. The soil arching effect in the triangular expanding pattern is weaker than that in the tower-shaped development pattern. The soil arching effect in the tower-shaped development pattern is strengthened and maintained at a high level during the settlement. This study on the evolution of three dimensional distribution of the earth pressure and deformation with the settlement between piles provides a basis for the design of pile supported retaining wall embankment.

The application of reinforcement elements in compacted backfill can significantly improve the seismic resistance of a retaining structure. In this paper，shaking table tests were performed on cantilevered reinforced earth retaining walls under sine wave loading at a frequency of 5 Hz，and the response acceleration of the model wall and the backfill，the dynamic earth pressure and displacement of the wall，and the dynamic tensile force of the reinforcement were monitored under 0.11 g(minor)，0.24 g(moderate) and 0.39 g(major) accelerations. The variations of dynamic characteristics of the model structure，the interaction between the wall and the backfill，and the stress level of the reinforcement with different imposed accelerations were illuminated. The results show that the propagation of the acceleration in the backfill shows hysteresis and nonlinear amplification effects and the acceleration tends to increase with rising the vibration amplitude. The most unfavorable condition(critical state) of the system stability means that the wall moves away from the backfill under the maximum inertia force. The synchronization between the peak dynamic earth pressure on the wall back and the peak inertia force of the wall becomes more pronounced with larger acceleration amplitude. The earth pressure acting on the wall is more significant with an acceleration of 0.39 g. The dynamic earth pressure acting on the upper portion of the wall is generally higher than that on the lower portion，and the resultant force acts at approximately 2/3 of the height of the wall，much larger than that obtained from the current code. The dynamic tensile force of the reinforcement increasing with the acceleration amplitude presents an inhomogeneous spatial distribution，and the connecting line of the points of the maximal tensile force reflecting the potential failure surface shows piecewise linear through the end of the slab base.

To better understand the hardening law of soils under different loading paths，a series of stress-path drained triaxial tests for clay are carried out. The results show that the plastic work Wp exhibits a significant dependence on the stress path and hence is not suitable to be chosen as the hardening parameter. The equivalent plastic workis introduced to eliminate this stress-path dependence，and then a generalized hardening model within the framework of egg-shaped yield function is proposed. In this model，the equivalent plastic work function is employed as the hardening parameter，and the equivalent hardening parameter is normalized referring to the concept of critical state line or Hvorslev line. It is found that the correspondence between the normalized equivalent hardening parameter and the equivalent plastic work is independent of the loading path and only relative to the stress state at initial hardening(represented by the stress ratio h0). Consequently，equivalent plastic work hardening functions applicable for strain hardening/softening model，only dependent on the initial hardening stress ratio η0，are established. Finally，comparisons between numerical and test results show that the proposed hardening model can effectively reflect the stress-strain characteristics of clay under different stress paths.

基于荷载传递法，提出基于指数模型的能源桩长期响应分析方法。首先，通过引入改进的Masing准则来构建以指数模型为骨干曲线的土体加卸载函数，进而基于荷载传递法研究温度循环过程中能源桩的工作特性；然后通过与现场试验数据进行比较，验证该理论模型的合理性；最后结合算例，研究能源桩的长期工作特性。结果表明：(1) 温度循环方式对桩顶附加沉降有重要影响，相较于仅用于制冷模式的能源桩，冷热循环工况下的桩顶沉降更加明显；(2) 桩顶刚度系数越大，桩顶沉降越小，稳定的也越快；(3) 上部结构荷载较少时，随着温度循环的进行，桩身下部可能会产生拉应力；而上部荷载较大时，桩顶沉降随着桩身温度循环的增长而加快，并且沉降稳定时间逐步增长。

Particle breakage will change the particle size distribution(PSD)，which can significantly affect the physical and mechanical properties of corresponding soils. In this study，a series of impact load tests were performed to investigate the evolution of PSD in breakage state for uniformly and non-uniformly graded carbonate soils under impact loads. Based on the test results of uniformly graded samples as well as fractal theory，an evolution function was established to describe the PSD evolution in breakage state for uniformly graded carbonate soils. The function contains only two parameters including fractal dimension D and breakage probability pB，which are both the functions of the input energy Eb. The non-uniformly graded sample was assumed to be a collection of independent multiple uniformly graded groups，and，from the PSD evolution functions of these groups，an assembly matrix was proposed to describe the PSD evolution for non-uniformly graded samples in breakage state. The test results of two sets of non-uniformly graded samples show that the proposed method can well predict the PSD in breakage state for non-uniformly graded samples under different Eb.