Daguangbao landslide is the largest landslide triggered by “5•12” Wenchuan earthquake. The exposed  sliding zone with a length of 1.8 km and highly ruptured rock mass occurred on the south side of the landslide，which attracted great attention across the world and was a focus in the past 6 years. The engineering geological mapping and exploration in the past made the cataclastic characteristics of rock mass in sliding zone to be well revealed. The sliding zone was found to be bedding on a fault zone of the slope. Because of the strong vertical ground motion near the seismogenic fault，the slope was separated along the bedding fault zone which was the relatively weaker interlayer. Vertical impacting or tamping within the weaker layer occurred leading to the further fragmentation. Mesoscopic analysis of sliding zone confirmed the existence of the earthquake induced fragmentation in sliding zone and revealed the dilation effect in the process of fracture，which was further verified with the physical simulation and PFC numerical simulation. The rock mass fragmentation and dilation of sliding zone were thus concluded to be very significant. Firstly，the further fragmentation and fine grains of the rock mass reduces the friction of sliding zone. Secondly，what is more important，because of the tamping and synchronous dilation within the sliding zone，groundwater will be strongly squeezed into the dilated space，which may stimulate the water hammer with the rapid increase of pore water pressure and the sharp reduction of shear resistance and as a result，causes initiation of the landslide suddenly with high traveling speed.

Rock splits due to the axial main compression load at the crack tip. This splitting is a compression tension failure，which is different from the compression shear failure of the Griffith theory. At the crack tip，there exists the extreme value of the minor tension stress. Tensile failure or splitting failure appear during the compression process corresponding to the gradual characteristics of rock failure. This kind of failure is beyond the modified Griffith theory. The criterion of the occurrence of rock splitting is that the value of longitudinal load should be high and the value of lateral stress should be low or zero and that there is no subsequent loads or the loads last short. The criterion was confirmed with the unloading test of thick-wall cylinder rock. Based on the energy principle，the energy dissipation characteristics of tension failure and compression failure was analyzed under no external work condition during the unload process，and the energy relations of rock failure were obtained. From the energy accumulation and dissipation，the mechanisms of coal-rock dynamic impacting and sudden damage of surrounding rock were revealed.

During the process of salt cavern leaching for oil/gas storage，the motion and subsidence of the insoluble particles have great influence on the shape of insoluble substance sump. The grain size distribution was analyzed and stacking experiments were carried to the insoluble particles of typical salt rock. Theoretical research was conducted on the moving and subsidence properties of the insoluble particles subjected to the action of flow field in cavern making. The subsiding velocity of the insoluble subsidence in brine field was established. The influence of the flow field on the moving principle of the insoluble particles in the construction phase of groove and the induced influence on the settlement pit were the focus of the research. The theoretical achievements were written into the software of Salt Cavern Builder. The results of modelling with the software showed that the shape evolution of the cavern bottom was more suitable for the real engineering conditions.

The vibration induced by the transient unloading of in-situ stresses(ISTU) is an important part of the eventual excavating vibration during the tunnel blasting excavation. In order to reveal the energy distribution characteristics of vibration induced by ISTU and its influence on the energy distribution of eventual excavating vibration，the energy distribution characteristics of vibration induced by ISTU under different in-situ stress levels and blasting loads were studied with the method of power spectrum analysis. The results showed that the frequency-band energy distribution of vibration induced by ISTU and blasting load were basically identical，but the main frequency of vibration induced by ISTU was lower than that induced by blasting load. The vibration induced by transient unloading of in-situ stresses was an influential factor，and it increased the low frequency component of vibration energy. The increase of in-situ stress level raised the vibration amplitude induced by ISTU and did not affect the frequency-band energy distribution.

The contact theory of numerical manifold method(NMM) is not only an important attribute of NMM but also the most time consuming part of NMM algorithm. Thus，it?s necessary to improve the efficiency of contact algorithm of NMM. Cover system and contact judgment method of NMM are introduced first in this paper. The efficiency of contact detection algorithm of NMM and its defects are analyzed in detail as well. After that，contact threshold as well as contact segments and the corresponding contact zones is defined based on the characteristic of contact algorithm. And the extremums of x and y coordinates of the contact zones are calculated. Then，spatial sorting is carried out by referring to double-ended spatial sorting(DESS) algorithm and the new contact detection algorithm of NMM is proposed. The new contact detection algorithm can detect the specific contact pair(vertex- edge or vertex-angle) thus have higher efficiency compared with the original contact detection algorithm in NMM.

The mechanism of the fault activation in the extra-thick coal seam of deep shaft at the fully mechanized caving face 2301N passing through a fault in Xinjulong Mine was studied using micro seismic monitoring，numerical simulation and theoretical analysis. The process of fault activation was divided into a stress appearance stage(at a distance of 274.8–214 m from the fault)，an energy storage stage(at a distance of 214–84 m from the fault) and a structure activation stage(at a distance of 84–0 m from the fault) according to the microseismic monitoring results，which was verified by numerical simulation. Two kinds of rock burst，fault-activated rockburst and fault-coal-pillar rock burst，both occurred when the working face passed through the fault. The mechanism of fault-activated rock burst was attributed to the accumulated tectonic stress release in both sides of the coal-rock mass adjacent to the fault，and the mechanism of fault-coal-pillar rock burst resulted from the high stress concentration caused by mining activities in fault coal pillar. The corresponding control technologies were put forward based on the analysis of the rock burst mechanisms in the process of working face passing through the fault. The field application of these technologies has effectively ensured the safety of mining passing through the fault.

In order to investigate the horizontal dynamic response of horizontal goaf group，a discrete dynamic response model was established by converting horizontal goaf group into a discrete vibration system of multiple degrees of freedom. The factor p considering the dissipation of energy in the surrounding rock(external damping) was introduced to modify the dynamic response model. Two cases，one is pillar blasting in single-layer and another is roof mine quake in multilayer horizontal goaf group，were numerically simulated with the unmodified model and modified model respectively. The results indicated that both the modified and unmodified model effectively responded to the instantaneous and continuous dynamic load. The value of factor p depends mainly on the transfer path and transmission distance of the energy in rock mass，which is not obviously influenced by the occurrence conditions of single-layer and multilayer horizontal goaf group. The modified model fits better the results of numerical simulation compared to the unmodified model，which to some extent reveals the dynamic response of horizontal goaf group. A new effective way has been provided for horizontal dynamic response of horizontal goaf group.

Blast-induced craters in wet soils can cause fatal disasters in geotechnical works，especially for crest of a dam and shallow locations of a foundation. A series of field explosion tests in wet sand were carried out to study the influencing factors on crater sizes. At the same time，a coupled SPH-FE numerical method was established to assess the results from field tests. The assessments show that the final crater in wet sand can be classified into three different types：camouflet，collapse crater and cast blasting crater. A cast blasting crater will be found at scaled burial depth of 1.5 m/kg1/3 or less. The critical scaled burial depth for camouflet is about 2.3 m/kg1/3 in wet sand. Diameters of the apparent crater from the tests and the true crater from simulations presented a good consistency with results predicted by ConWep. Bulge movement modelling with SPH particles was basically consistent with that in the field test，which means the numerical method can be used to predict the apparent crater sizes well in a real project. Density and strength of sand material have little influence on crater diameter within a tolerance of 10%. An empirical equation of crater diameter is proposed in terms of explosive mass and burial depth，based on dimensional analysis and the results from field tests.

The full response of a brittle structure containing multiple cracks under the servo loading condition is of vital importance in the evaluation of properties of the structure. Due to the mathematical covers and physical covers，numerical manifold method is able to simulate the initiation and growth of multiple cracks in a natural way. In order to handle the junction of cracks more straightly，the MLS-based numerical manifold method was used，and the physical patches containing crack tips were enriched to describe the singularity. During the crack growth，crack tips can be located anywhere in the background meshes. Several numerical issues encountered in the simulation were discussed and solved. Besides，a simple algorithm for multiple crack propagation was presented to satisfy the fracture toughness closely. Several numerical examples are illustrated to demonstrate the efficiency and robustness of the proposed method in the simulation of multiple crack propagation.

To meet the need of in-situ stress test in coal mine，acoustic emission experiment under uniaxial compression was carried out to study the failure and acoustic emission characteristics of rock samples from the roof of bedding sedimentary rock series. The comprehensive estimation of Kaiser effecting points and the calculation for in-situ stress based on Kaiser effect were studied. The results showed that，under the uniaxial compression loading，the rock sample without bedding exhibited the characteristics of brittle failure. While bedding rock sample experienced a process of local slip，instability of shear zone and rock sample failure. The total AE counts of rock sample without bedding had the tendency of slow increase to rapid increase，while the bedding rock sample had a step increase. The reason of such difference is due to the difference of the inner damage of rock. A comprehensive judgment method for Kaiser effecting points was derived based on AE characteristics，and an in-situ stress calculating method based on Kaiser effect was improved. Moreover，the final results of in-situ stress were that . = 25.06 MPa， = 13.75 MPa and  = 8.07 MPa.

A blasting-induced damage model on account of initial damage was suggested based on the current theory of blasting induced damage on rock. The relationships among the initial damage，acoustic wave velocity，elastic modulus and threshold value of blasting induced damage were also presented. The effects of blasting induced damage and the main influencing factors under the blasting excavation of protective layer of rock bench for anchoring crane girder of the main underground powerhouse of a lager hydropower station at Xiluodu were analysed and the formulas of blasting parameters were suggested. The blasting parameters were provided owing to two engineering classifications of rock mass with different initial damages mainly located in the main underground powerhouse. The blasting tests simulating the excavation of protective layer of rock bench，the blasting vibration velocity tests and the borehole acoustic wave tests were carried out in the field，and then，the rationality of blasting parameters was proved and some supplements were added to improve the design of blasting parameters. The results showed that the initial damage of rock mass should be taken into account for the calculation of blasting parameters. The blast-hole concentration coefficient from the study was smaller than that from common smooth blasting design for the blasting excavation of protective layer of rock bench. When the initial damage of rock mass increased，the coefficient of non-coupling charge should be increased and the concentration coefficient of blast-holes for smooth blasting should be reduced. For the excavation of protective layer of rock bench，the control of both the blasting-influenced depth and the blasting seismic effects meets the requirements suggested by the hydropower station，thus，the design of blasting parameters is of rationality. The research results can provide references for similar projects.

Determining the types and parameters of advance support is an important work in tunnel construction under conditions of unfavourable rocks. In this research，the determination of advance support for tunnel was established，including the safety assessment of construction，the modes election and the parameter determination of advance support. The predicted deformation value of surrounding rock of tunnel and the value from control standard were compared to determine whether the advance support was required. The engineering analogy was used to determine the modes of advance support under the condition that the predicted deformation value  adopting the selected mode of advance support meets the control standard. The sensitivity and effectiveness of support parameters were analyzed to determine the upper and lower bounds of the support parameters. The method has been successfully applied in shallow covered Hejie high-speed railway tunnel.

In order to obtain the real physical model to characterize the pores and fissures of coal mass and to numerically investigate the internal gas flow，the segmentation of DTM threshold was implemented to segment the CT images. The method of DTM threshold was amended by adding Wiener filter denoising. Its correctness was validated with the three-dimensional reconstruction. The abscissa value corresponding to the maximum value of the minimum on the porosity curve was found to be the optimal threshold. Numerical simulation of gas flow was conducted based on the real physical model of pores and fissures of coal extracted using the DTM threshold segmentation method. Simulation results showed that at the micro-scale(＜100 µm)，the gas flowing pores and fissures agreed with the high speed nonlinear percolation of Forchheimer. The flow velocity grew rapidly in fissures and changed randomly along the direction of flow. The permeability coefficient and non-Darcy coefficient were calculated according to the fitting parameters on average flow velocity.

The study area is located at the right bank of a proposed hydropower station on River Nu of Yunnan. The slope is mainly composed of migmatitic granite and mixed gneiss and the phenomenon of deformation and fracture controlled by low-angle and tilt-valley faults is very distinct. Although the macroscopic combination mode shows sliding-fracturing，but these faults were not cut and exposed at the slope toe and were buried inside the toe or below a certain depth of the valley. It is difficult to understand the cause of this phenomenon according to the views of traditional engineering geology and rock mechanics. Based on the field geological survey and the analysis of geological and mechanical conditions，the above phenomenon of deformation and fracture was found to be caused by the weathering and softening of rock in the valley bottom(slope toe and valley below) during the neoid geological period，which was a time-dependent deformation and fracture phenomenon. The result was verified by the numerical simulation. For the evolution of rock slopes，the softening effect of valley bottom(slope toe) is a kind of geological function with universal significance.

Limit state design is an important step for internationalization of Chinese railway. Cumulative cyclic deformation of subgrade is one of the control standards in railway design. Based on the empirical formula of permanent strain，a prediction model was proposed to predict the cumulative cyclic deformation of high-speed railway subgrade. 1∶1 physical model tests were carried out to calibrate its applicability. A limit state equation of cyclic cumulative deformation of subgrade was developed considering the variation of dynamic stress and material parameters. Coefficient of variation(COV) of dynamic stress on subgrade surface was determined with the measured data from the high-speed railway of Wuhan—Guangzhou. The effects of the dominant parameters on the reliability index were analyzed to investigate the effect of the variation of dynamic stress and material parameters.

Calculating the permeability of soil theoretically is very difficult due to complexity of soil properties. A concept of equivalent pipe-diameter was introduced and a mathematical expression was derived in the paper for the estimation of soil permeability based on Poiseuille?s law. The rationality and applicability of the model were carefully checked against the special laboratory data of permeability tests. Results showed that the percolation path of soil could be converted into a series of thin pipes by means of the equivalence principle. The mathematical expression of equivalent pipe-diameter considered the influencing factors to soil permeability，such as the compactness，bound water content，particle grading，pattern distribution and geometric shape of soil particles. The model produced results in agreement with the laboratory data. The estimation model was found to be applicable to the soils with the particle sizes between 0.002 mm(lower bound of coarse clay，0.002 mm) and 0.500 mm(upper bound of medium sand，0.500 mm).

The prediction of displacement is essential in the displacement-based seismic design of gravitational retaining structures with saturated backfill sand. Based on the sliding theory of Newmark，the stress-based excess pore pressure model and the cumulative damage theory，the models for predicting the time histories of excess pore pressure ratio，rotational and sliding critical accelerations were proposed. The methods of calculating the rotational and sliding displacements were established using the proposed models. The effects of soil parameters and ground motion parameters on sliding and rotational displacements of the wall were studied with the proposed methods and the coupling effect between sliding and rotational displacements was also analyzed. The results revealed that under the non-liquefaction condition of backfill sand，the sliding displacement of gravitational retaining structures with saturated backfill sand was very sensitive to the relative density and friction angle of soil at the base of the wall. The rotational displacement was sensitive to the magnitude of earthquake，horizontal and vertical seismic accelerations of ground motion，friction angle and relative density of soil and angle of friction of soil against wall back. The influence of excess pore pressure on sliding and rotational displacements cannot be ignored. The results about the coupling effect between rotational and sliding displacements indicated that when the sliding and rotation of wall occurred simultaneously，rotation and sliding inhibited each other.

Those karst cavities beneath the bottom of cast piles in bore hole have significant impact on the project itself and the surrounding buildings. Due to the necessary mud protection in bored pile construction，many geophysical methods at current stage are not applicable for the karst cavity detection. A sonar technology for the detection of karst cavities located beneath the bored pile was proposed utilizing the features of sonar stress wave propagation. A sonar detector(JL-SONAR) and a signal analysis software PBCA were developed. JL-SONAR detector was responsible for the transmission and collection of sonar signals，and PBCA software was designed to analyze and sort the detection data. The technology makes full use of drilling mud，and enables the detection of the karst cavities within the range of 10 meters below the pile bottom during drilling. The technology was applied in two projects successfully and has the advantages of low cost，high speed and high precision.

In order to study the influence of foundation scale on the bearing capability of rigid pile composite foundation，several groups of model tests such as the load tests under four different scale plates，foundation soil load test，composite foundation load tests and single pile load tests，were carried out using a model test apparatus made in-house. A series of test results were acquired. The results showed that with the same loading stress and pile replacement ratio，the composite foundation settlement and pile-soil stress distribution ratio increased with the increasing of loading plate scale. The load carried by the pile increased at the same time. Based on the test results，the scale effects of rigid pile composite foundation were analyzed from a theoretical point of view. The composite foundation load test did not perfectly represent the load bearing characters of the actual composite foundation because of the scaling effects. A new method to calculate the bearing capacity of the ground by overlapping the single pile and soil p-s curves were put forward to solving the problems of scale effects of composite foundation. Calculated results of model tests and engineering example showed that the method was feasible.

The correcting coefficient for rod length in dynamic penetration test depends on the transmission of the axial impacting force and the impacting energy of hammer from the top to the bottom end of the rod after the hammer impacted the rod top. Four test schemes with the rod lengths of 22.92，25.87，40.92 and 46.85 m respectively were designed and six monitored points were arranged along the axis of the rod. The heavy dynamic penetration tests were carried out at two sites in Wuhan，one at Yaogou village near South Lake and another at the cofferdam in Yangluo. The whole strain processes of every monitored point were measured with the dynamic strain gauge. Subsequently，the axial impacting force of the every monitored point was calculated and the hammer impacting energy was obtained with F2 method based on the wave mechanics. The temporal and spatial distributions of the axial impacting force and the impacting energy of hammer along the rod were studied thoroughly. The formulations of the axial impacting force and the hammer impacting energy with the rod length were established，which were consistent with existing research results.

In order to study the effect of the offset distance on the magnitude and distribution of vertical stress of tiered geosynthetic reinforced soil wall，a series laboratory tests on geosynthetic-reinforced soil(GRS) two-tier wall models with three offset distances were carried out. The test results indicated that the vertical stress at the bottom increased with the wall height rising and that the maximum value appeared nearby the wall. With the increasing of offset distance，the distribution of the vertical stress along the reinforcement was evolved from V-shape to inverted S-shape. The effect of overlarge offset distance on the vertical stress at the bottom of the two-tier geosynthetic reinforced soil wall was not obvious. The vertical stress at the bottom of the geosynthetic reinforced soil wall was calculated quite accurately with the modified FHWA method and modified Gray elastic solution. The vertical stress in the lower wall decreased with the increasing of the load location distance to the upper tier face. After the loading was applied on the upper tier，the vertical stress at middle and back reinforcement increased，but at the front of reinforcement changed little.