The relationships between energy dissipation and strength，energy release and global failure during the deformation and failure of rock mass element are discussed. Under the condition of cyclic compressive load，the energy dissipation and damage variable are calculated and used to fit the damage evolution equation based on the analysis of energy dissipation. The releasable strain energy，dissipated energy，unloading elastic modulus and unloading Poisson¢s ratio are calculated at different loading levels and different loading speeds so that an equation about unloading elastic modulus under complex stress condition is obtained. The global failure criterion of rock mass element is proposed based on the analysis of releasable strain energy and is well accordance with the result of biaxial compressive test on marble. The failure criterion of layered rock mass is proposed based on the analysis of distortion energy and general potential energy of volume；and it is well accordant with the result of biaxial compressive test on layered rock.

With integrated applications of artificial intelligence，system science，rock mechanics and engineering geology，a new methodology has been proposed for evaluation and prediction in space-time for the safety of rock engineering under hazardous environment. It includes integrated back analysis of rock mechanical parameters，intelligent recognition of the mechanical models structure and its parameters，finite element analysis in parallel with dynamically updating the model and parameters of rock masses，evaluation and prediction in space-time for the safety of rock engineering under hazardous environment in parallel with dynamically updating the model and parameters of rock masses，zoning self-adaptive support design for the safety of rock engineering under hazardous environment，intelligent system for the integration of multiple information and tasks for the safety of rock engineering under hazardous environment. The proposed method has been successfully applied to risks evaluation and optimal design for slopes and cavern groups in Longtan，Shuibuya，Bachimen，Laxiwa projects，etc.. The results are satisfied.

Procedures for artificial simulation of multi-point seismic acceleration histories with consideration of spatially non-uniform seismic ground motion are demonstrated to provide reasonable ground motion input for the numerical models. By establishing three-dimensional numerical model of underground rock cavern groups，seismic responses of the underground cavern groups under spatially uniform and non-uniform ground motion are carried out. It is shown that：(1) seismic response of the cavern groups is very similar to the time-history curves of displacement of the exciting sources，which indicates that the inertial effect of the rock mass can be ignored；and (2) seismic response mainly depends on the amplitude of the seismic waves；the spatial non-uniform effect has no negative impact on the underground cavern groups under the axial length ranging from 300 m to 400 m. Spatially non-uniform seismic ground motion，therefore，cannot be taken into account in the seismic safety assessment of the similar underground rock cavern groups.

Based on the mechanism of the interaction between geo-body and structural body，the nature and description method of irregular interface between geo-body and structural body are studied. A new cubic covering method is proposed to determine the fractal dimensions of the interface，which improves the measuring precision. The interface effects，such as the deformation，failure and slide of interface，are discussed for different interface shapes by using the photoelastic coating tests. The two-body(geo-body and structural body) mechanical model with the interface effect is established. The interface element with homogeneity and fractal distribution is developed in numerical simulation. The failure pattern and influential factors are studied based on the interaction between gravity dam and foundation，which objectively estimates the global stability of the dam. The propagation pattern of the irregular interface cracks at heel of concrete gravity dam is studied by using fracture mechanics. Critical length and loads of interface crack propagation are obtained using composite fracture criteria. The results indicate that the coarse interface prevents the propagation of interface crack，and redounds to stability of gravity dam.

At 14：28，May 12th，2008，a large earthquake measured Ms = 8.0 hit Longmenshan mountainous area，west Sichuan Province，China. The earthquake was induced by the thrust and strike-slip of Longmenshan central fault and its 300 km-long fault rupture resulted in a large number of rock avalanches and landslides，destroyed numerous villages and towns，leading to many human fatalities. By 12：00，July 11th，the earthquake has caused 69 197 peoples to die，18 341 peoples to be missing，and 374 176 peoples to be injured. Based on field reconnaissance，the geological conditions and fault patterns in Longmenshan mountain area are introduced briefly；the types and distributions of disasters and their relations with fault patterns are summarized from the engineering viewpoint. And then the major geotechnical problems to be faced in post-quake reconstruction are put forward，so as to provide references to reconstruction and further researches.

Focused on the large-scale landslide hazards in the Three Gorges Project(TGP) reservoir area，coupling mechanism of the endogenic and exogenic geological processes of geological hazard is studied. The following three aspects are examined. (1) By analysing the landslide space-time distribution characters and its control factors，the relations between the landslide formation and the Earth¢s endogenic-exogenic geological processes are illustrated. (2) Slipping zones are the control factor of rock slide development. Based on the study of sedimentary formation，tectonic evolution and earth¢s exogenic geological process，four-phase patterns of slipping zone formation and evolution are put forward；and the coupling mechanism of the Earth¢s endogenic-exogenic geological processes is explained. (3) Qianjiangping Landslide is the first rock slide after impounding of TGP. Through the fine description and test on the slipping zone and interbedded shear zone，slipping zone formation process of Qianjiangping Landslide is rebuilt. The effect of the endogenic-exogenic geological processes on slipping zone formation is studied. The conclusions are shown as follows：(1) the coupling of neotectonic movement(intense tectonic up and river downcutting) and Quaternary climatic change(intense rainfall) is the main dynamic factor of many large-scale landslides development in TGP reservoir area；(2) the coupling of interbedded shear effect and water-rock interaction is the control factor of slipping zone formation in rock sliding；and (3) it is of great importance to study the neonatal landslide in TGP reservoir area. The geomechanical study on interbedded shear zone in easy-slipping strata is helpful to discover and forecast neonatal landslides.

The Wenchuan large earthquake of 8.0 magnitude has shocked Sichuan Province and neighboring regions on May 12，2008，with nearly seventy thousands of lives lost and the whole country immersing in deep sorrow. Based on field survey and analysis of earthquake-induced geological hazards，the engineering geomechanics should be considered and used to play important roles in the relief and reconstruction after the earthquake. According to preliminary investigation into western mountainous areas of Anxian County，several kinds of geological hazards are recognized，mainly including bedding landslide，loose materials landslide，cliff collapses and rockfalls. The field investigations indicate that the geological structural planes in rock masses or geological masses may be important dominant factors for generation of geological hazards in the investigated area. For the reconstruction of the disastrous areas，some engineering geomechanical problems relevant to choices of reconstruction site，monitoring，prevention and remedy of geological hazards，and so on，should be considered.

The multiplicity and randomness of fractures distribution in rock mass are key issues in research on engineering properties of fractured rock mass. The randomness of fractures geometrical shapes(orientation，dip，trace length，spacing，and width) of fractures is considered；and Monte Carlo simulation technique is adopted to develop a new code RFNM(including RFNM2D and RFNM3D). By RFNM，not only the virtual fractured rock mass，in which the structure information of fractures is described and the real engineering rock mass is represented，can be generated；but also the digital fractured rock mass can be discretized and then be combined with numerical methods(such as FEM，DEM，and so on) to solve practical engineering problems. Therefore，the virtual fractured rock mass with random fracture networks is a digital fractured rock mass model actually. In addition，based on seepage theory of porous media，FEM is adopted to develop the software GeoCAAS (geo-engineering computer aided analysis system). The hydraulic properties of fractured rock mass are studied；and the effects of fracture geometrical shapes on the seepage properties are discussed.

Permeability in brittle rocks under compressive stress changes with crack growth. A method to calculate permeability evolution is presented，in which both experimental phenomenon and inherent mechanism of permeability evolution are taken into account. The mechanical model is based on the research of ZHU Qizhi et al，two modifications are applied to frictional criterion and potential function；and the modified anisotropic damage model is used to simulate triaxial compression test of Lac du Bonnet granite. According to damage variable and crack normal and tangential deformation obtained in mechanical model，a function of connectivity coefficient is used to describe the ratio of the crack involved in hydraulic flow to total number of crack，more and more cracks are involved in hydraulic flow when microcracks grow；the cubic law is used for seepage flow in a single crack，crack radius and equivalent aperture are defined by micromechanical result；a method is proposed to analyze permeability evolution in brittle rocks under deviatoric stress. The proposed method is employed to simulate in-situ permeability test of Lac du Bonnet granite. Comparison between axial and lateral permeability evolutions under increasing deviatoric stress is carried out；axial permeability evolution under different confining stresses is also predicted. It is shown that the numerical simulation results and experimental data are in good agreement.

The research results of model tests and numerical simulation in two different loading conditions，triaxial and direct shear，are summarized. By conducting model tests on integrated samples and intermittent joints samples，shear strengths under different normal stresses are obtained. Also，the changing trends of shear strength under various connectivity rates are analyzed. The entire process of direct shear test is numerically simulated using particle flow code in 2 dimensions(PFC2D). In order to make the stress-strain curve of numerical simulation accord with experimental one about both integrated samples and through samples，the mechanical parameters between particles are adjusted. Through adopting the same particle geometric parameter，the numerical models of intermittent joints under different connective conditions are rebuilt. At the same time，the rock bridges and joints in testing samples with the fixed particle contacting parameters are endowed，and a series of direct shear tests are conducted. Then the failure process and mechanical parameters in both micro-prospective and macro-prospective are obtained. By synthesizing the numerical and testing results and analyzing the evolutionary process of stress and strain on intermittent joints plane，it is concluded that the shear strength of rock bridges is increased due to the centralization of compressive stress on it. At last，the failure mechanism of intermittent joints rock under direct shear condition is discussed，meanwhile，the whole shear process is divided into five phases，i.e. linear elastic phase，fracture initiation phase，peak value phase，after-peak phase and residual phase.

Wavelet transform is attempted to be applied to safety monitoring. The method eliminates modular maximum caused by the noise，reserves the modular maximum caused by the useful signal using wavelet transform based on the different propagation characteristics of the signal and noise on the different scales，reconstructs wavelet coefficient using maximum residual modular and recoveries the primary monitoring signal. The denoising method of wavelet transform modular maximum and wavelet threshold are applied to two actual cases，simulating noise signal noissin and safety monitoring data of the high rock slope of Jinping First Stage Hydropower Station. By the comparison of the three performance indexes，the signal-to-noise ratio，energy ratio of the denoising signal and standard deviation of the denoising signal to the original signal，the studies reveal that the former method is better and can effectively remove noise mutational signal and reserve useful mutational signal. It shows that the former method can be well applied to the safety monitoring data processing in geotechnical engineering.

The internal friction character is one of the basic properties of geomaterial，and the internal friction exists in mechanical elements all the time. However，until now the internal friction is only considered in limit analysis and plastic mechanics，but not included in elastic mechanics and energy theory. It is considered that the internal friction exists whether in plastic state or elastic state，and the mechanical elements of friction material are constituted based on this cognition. According to the research of soil tests，it is presented that the cohesion takes effect firstly，and then the internal friction increases gradually with the increment of deformation. By assuming that the friction factor is proportional to the strain，the internal friction is computed. At last，by imitating the linear elastic mechanics，the nonlinear elastic mechanical model of friction material is established，where the shear modular G is not a constant. The new model and the traditional elastic model are used simultaneously to analyze an elastic foundation. The results indicate that the displacement and the shear stress computed by the new model are smaller than those of the traditional model，which is in agreement with the fact. So it is suitable for geomaterial to adopt the mechanical elements of friction material.

The axial compressive strength and deformation scale effect of five kinds of rock masses with fractal joints are studied by using the similar materials and the simulating block joints are prepared with vitriol paper. The experimental data of compressive strength and deformation changing with the joint fractal dimension for the same scale have been obtained，and two-dimensional empirical equations are developed based on the analyses of the experimental data. The experimental results indicate that the compressive strength and deformation modulus of rock masses decrease with the increase of scale and the joint fractal dimension；but the Poisson¢s ratio increases with the increase of scale and the joint fractal dimension. It can be generally concluded that the rock ductility increases with the increase of scale and the joint fractal dimension；and the damage process and form are controlled by the joint distribution dimension.

Both weathering crust zonation and quality classification of rock mass are important for shallow-buried tunnels. Qualitative differentiation and quantitative index should be distinguished for each of the two systems in underground engineering. In granite area with relatively good geological conditions，middle and low in-situ stress and groundwater in East China，the relationship between weathering crust zonation and basic quality classification of rock mass，which has some common ground and spatial crossover in shallow-buried tunnels，is found. Taking the Daya Bay tunnel for an example，the relationship of the two systems and relative indices is discussed. As a result，it is found that the weathering crust zonation is macroscopic，and the quality classification is mesoscopic，and the latter is controlled by the former. Generally，the grade of rock mass quality is about 1.5 times higher than that of the weathering crust zonation of granites in shallow-buried tunnels in East China.

Real-time computerized tomography(CT) experimental results of sandstone failure process under triaxial compression with chemical corrosion and permeation of chemical solution are presented. The changes of CT numbers of every scanning layer are analyzed under triaxial compression with and without permeation at different CT scanning stages；and the stress and time that deformation lasts in different testing stages are studied for sandstone samples with and without corrosion under triaxial compression with and without permeation. The effect of permeation on sandstone strength is obtained. The test results of CT images and CT numbers show that crack-tip closure is resulted from the development of microcrack under the environment without permeation during the process of microcrack propagation to principal crack coalescence，after which cracking continues under the environment with permeation due to pore water pressure. Because of permeation and pore water pressure，more cracks are generated in the specimens under the environment with permeation but they are relatively single in the specimens under the environment without permeation. From initial linear elastic deformation to crack-tip fracture，the effect of permeation on the stress and time that deformation lasts is main key factor and the chemical corrosion is a secondary factor. From crack-tip fracture to crack coalescence，the stress and time that deformation lasts are decided by both permeation and chemical corrosion. The effect of permeation on sandstone strength is obvious. The strength is much greater under the environment without permeation than that with permeation. For example，the strength under the environment with permeation occupies 16.6% of that without permeation for the specimens corroded by NaCl solution with concentration of 0.01mol/L and pH value of 2.

Two basic parameters of load/unload response ratio(LURR) are introduced firstly；and the new definition of LURR is conducted using damage and strain of materials as response based on the theory of damage mechanics and the idea of LURR. Furthermore，the relation between LURR and damage variable(D) is set up and analyzed with Weibull distribution as probability distribution function；and the effect of Weibull exponential on the relation is also investigated. Secondly，the process of damage evolution in the rock failure acoustic emission(AE) experiment carried out in 2003 is described with AE number density utilizing the experimental data. The curve of LURR against time defined by damage and strain of the granite specimen is calculated and compared with the one calculated with Benioff strain as response rate. The two curves are quite similar，both LURR values experience the same process，i.e. abnormity appears，LURR values rise to the peak with relatively slow speed and then decrease sharply，rock specimens fail or destabilize quickly，which is consistent with the trend of LURR curves calculated with seismic data and also shows the rationality of LURR defined with Benioff strain as response rate in the actual earthquake prediction. In the end，the loading and unloading experiments on a two-story structure carried out in the University of Naples in Italy are presented；and the experimental data are analyzed using LURR method. In a word，the relation between LURR value and D not only provides more detailed basis to study the damage evolution of a certain kind of brittle materials utilizing LURR method，but also offers a new approach to the health assessment to large-scale structures and prediction of engineering catastrophic failure.

The influences of pre-existing crack geometrical position and matrix material mechanical properties on crack propagation and coalescence are studied using self-developed numerical tool EPCA2D. The weak cell element is used to represent the pre-existing cracks in rock specimens. The mechanical parameters of the cell element of rock matrix are assigned values by using Weibull¢s distribution to reflect the heterogeneity of rock bridge as a part of rock matrix. The pre-existing crack and the rock matrix conform to the perfect elastoplastic and elasto-brittle-plastic constitutive relation respectively. Using this method，the failure processes of rocks with two or three pre-existing cracks are simulated；and the phenomena of crack initiation，propagation and coalescence are well reproduced. It is concluded that the geometry of pre-existing cracks has great influence on the crack propagation and coalescence. At the same time，by considering different rock matrix properties，the failure patterns of rocks with different spatial random distributions of mechanical properties and different frictional angles etc. are numerically investigated. It is found that the crack propagation and coalescence paths are strongly dependent on the mechanical properties of materials，which can explain the reason why there exists diverse crack propagation paths in experiment.

As faults，inner layers and interlayer shear bands widely develop in the left dam abutment of Baihetan Hydropower Station，and the fault F33 directly conjoins with the left dam abutment，so，shear deformation easily occurs under the thrust of arch dam. The mechanical indexes of dam foundation such as deformation modulus are relatively small and the anisotropy of dam foundation is obvious due to the development of columnar joints layers. In order to reduce the influence of these geological defects，some engineering measures are taken when designing，such as setting anti-shear tunnel along the direction of arch thrust，the cushion to the rock mass of dam foundation，etc.. These measures will improve the shear and transmission force mode of abutment and foundation to some extent. 3D nonlinear numerical method is applied and 3D numerical model based on geological information is built to simulate certain geological phenomena and related engineering measures in middle dam site of Baihetan Hydropower Station. The safety degree of the downstream dam line is evaluated by overloading method，strength reduction method and point safety factor method. The results obtained by these methods will play a role of support to technical basis and scientific research achievements for choosing dam line.

Jinping II Hydropower Station，located in Sichuan Province，is the biggest station at the Yalong River. In the excavation course of the second layer of the underground powerhouse，serious local instability problems arise at R0+263 of the upstream side wall with the characters of deformation more than 20 mm and deformation rate of 3.4 mm/d. So，a new way integrating theoretical analysis and field engineering control is put forward. In the first phase，mechanical parameters of surrounding rock are identified；and engineering control methods are given. In the second phase，monitoring data and mechanical behavior of surrounding rock during excavation are analyzed；and the reinforcement scheme and reinforcement parameters are suggested. Finally，the instability problem is solved completely. The practice indicates that the method combining the real-time dynamic feedback analysis，multiform measurement information and theoretical analysis with engineering control together is very useful to deal with local instability problem in underground engineering. At the same time，the physical effect of anchor bolts which improve the mechanical strength of surrounding rock is certified according to the comparison of equivalent mechanical parameters of surrounding rock after reinforcement of anchor bolts.

The automatic monitoring and predicting system are significant for actively treating quicksand hazards in mining engineering. The centrifugal model tests emphasize the variations of pore water pressure and the concentration and dissipation of the excess pore water pressure in clay layers above the mined-out area and coal pillars，and the maximum excess pore water pressure can be increased by 15%–20% of the vertical dead-weight stress at the monitoring point. A mining-induced pore water pressure simulation experiment shows that the variation of the pore water pressure in a confined aquifer due to mining is closely related to the mining progress and periodic roof pressure. The pore water pressure in the aquifer above the coal pillars generally increases firstly and decreases then during mining. The pore water pressure variation in the aquifer above mined-out area is related to the location of working face，which decreases obviously when working face just passes the said point，and increases for a period of time while the monitoring point lies above the mined-out area. Quicksand model tests show that，when water inrush and quicksand start，instant negative pore water pressure is recorded at first，then the water head stabilizes at a low level for a period of time as the other sensors around the fissure demonstrate a water funnel with certain hydraulic gradient. It can be deduced from these results that the pore water pressures can be of important precursor significance for monitoring and forecasting the quicksand hazards in mines.

According to the distribution and movement of Xi¢an ground fissure，combining the trend of metro tunnel No.2 in Xi¢an，a geological model has been built，and then the effects of the ground fissure on the metro tunnel have been studied. The experimental results show that the tunnel is in tension and compression states，and behaviors as a cantilever elastic foundation beam under the environment of ground fissure. The tensile parts mainly distribute in the range between 20 and 80 cm away from the fissure in fixed block，and the compressive parts distribute between 20 cm away from the fissure in declined block and 80 cm away from the fissure in fixed block. At the same time，the movement of the ground fissure greatly increases the vertical pressure of surrounding rock at the top of tunnel and reduces the vertical pressure of surrounding rock under the bottom of tunnel in the decline block. Under the environment of ground fissure，the failure mode is mainly circumferential crack；the secondary fissures are controlled by tension-shear areas，and step and y-shaped fissures are mainly induced. Based on the experimental results，the section and position where countermeasures should be taken are put forward when the metro tunnels cross the ground fissure region.

Under the restriction of geological conditions and detection technology，accurate data of real space shape of complicated cavity are very difficult to obtain with conventional detection methods. The cavity data detected by these methods are so rough for building model in numerical analysis；and high reliability of stability analysis based on the model can not be reached. Therefore，3D laser scanning for complicated cavity with cavity auto scanning laser system(CALS) is put forward. This system is capable of being inserted into voids and cavities via predrilled boreholes to quickly and safely survey old workings；after exact 3D point cloud data are obtained by using CALS，the data can be processed so as to accurately simulate 3D geological model of the cavity in Surpac software；and then，adopting coupled Surpac-FLAC3D technology，numerical analysis model with real space shape of the cavity is created in FLAC3D，and the stability calculation is conducted in the final phase. Selecting the underground cavity of Sandaozhuang open-pit mine as an example，real space boundary of the irregularly cavity is scanned and 3D block model of the surrounding rock is modelled using the method mentioned above；following that，coupled Surpac-FLAC3D technology has been studied and 3D model data is successfully introduced into FLAC3D software；combining mechanical parameters of surrounding rock based on field tests and other geological conditions，static calculation is performed. According to the calculation results，stability of the cavity is analysed referring to the nephogram of stress and displacement of the surrounding rock，and the accuracy and reliability of the analysis results are greatly improved.

For the progressive failure of geological structures(faults，karst collapse columns) to be investigated and their microseismic activities associated with water inrush to be predicted，microseismic monitoring is firstly undertaken in a deep coal mine where the water inrush is a significant issue. The development of a technique for the event location and the analysis of microseismic events are concerned. A new optimum method is provided；the preferred measurement of focal time is the basic calculation process，and also several concepts of event location types are defined according to the actual location，e.g. within the receiver array or outside it，nearby the receiver array or far away from it. The localizing method and judgment of location type，together with the correction of velocity and the monitoring system using artificial blasting sources make the improvement of the event location accuracy be significantly possible. With the results of microseismic events and 3D illustration technique，the activities of geological structure，fracture-depth of roof and floor，and the parameters of boundary pillar are obtained. These studies indicate that it is considerably possible to predict the water inrush using microseismic monitoring with its inherent ability to remotely monitor the progressive failure caused by mining. The approach used to integrate microseismic data should be comprehensive with different interpretations from different subject views，such as geology，mining engineering and geophysics. How to make a 3D quantitative mechanical model to describe the failure region from the energy view，instead of qualitative analysis，is put forward. Apparently，it will be an important research direction with its further application associated with gas and coal projects，rock burst and so on.

A finite element numerical model is established based on the dimensions of a centrifugal test model to simulate the changes of displacements，earth pressures，pore water pressures and tensile forces of reinforcements with time in the soft clay foundation on the reinforced embankment with lime-stabilized soil as backfill under the variable acceleration loadings. The computed results then are compared with those obtained from the centrifugal test. Three cases of unreinforced，one-layer reinforced and two-layer reinforced embankments are also simulated based on the calibrated numerical model. The results show that the computed displacements，earth pressures，pore water pressures and tensile forces of the reinforcements are in good agreement with the measured ones，indicating the appropriate numerical model. The vertical and lateral displacements，respectively at the center and the slope toe of the unreinforced embankment，are greater than those of one-layer reinforced embankment. The difference of the ground surface horizontal displacements at the slope toe between unreinforced and one-layer reinforced embankments reaches nearly 2 mm when the acceleration is 100.0 g；however，the displacements of the two-layer reinforced embankment are very close to those of one-layer reinforced embankment.

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