Nonlinear unified strength criterion is presented and Hoek-Brown criterion is modified by the unified strength theory. The characteristics of rock and the effect of intermediate principle stress on rock strength is taken into account. Hoek-Brown criterion and nonlinear twin-shear strength criterion are two special cases of the nonlinear unified strength criterion. The limit loci on plane of Hoek-Brown criterion and the nonlinear twin-shear strength criterion formulate inner and outer bounds. The parameters of the nonlinear unified strength criterion are the same as those of Hoek-Brown criterion obtained from normal triaxial test for rock block. The failure loci at defferent stress angle can be estimated from the nonlinear unified strength criterion. The comparison of the nonlinear unified strength criterion with the experimental data of six sets of true triaxial test for rocks shows the good agreements. This method can be generalized to rockmasses or jointed rockmasses.

The relationship among permeability，strain and stress of rock is discussed for both brittle and plastic fracture based on the permeability-strain curve and permeability-stress curve obtained from the permeability test under complete stress-strain path. The results of coupling behavior of permeability of rock with stress before peak pressure show that permeability-stress curves of various rock samples resemble each other in geometrical pattern，and correlativity between permeability and stress is obvious. A formula is proposed to show the behavior of permeability expressed with increasing of stress. In addition，a characteristic parameter of stress is proposed to indicate critical anti-permeability strength of rock which corresponds to the stress causing permeability strengthening distinctly. And an example of application of the characteristic parameter is also given to evaluate water-insulating capability.

Based on the principle of virtual displacements，the direct coupling formulae of FEM in the anisotropic saturated soils with the assumptions of homogeneous and continuous elasto-plastic porous media are derived. The FEM programs in MATLAB are implemented for the ill-posed equation which is formed in the direct coupling method. The comparisons between the computed and analytic results on the Mandel effect in the anisotropic elastic porous media are illustrated and the validity and applicability of the mentioned FEM are demonstrated.

By studying the permeability of coal mass and fractal law of fracture，the relationship between permeability and fractal dimension of coal is obtained. It shows that the permeability varies with the water pressure，volume pressure，fractal dimension and strength according to the derived equation. The presented results are of singnificant value for practical application.

A shear-seepage test of single fracture with sand is carried out under displacement control. The seepage law of rock fractures is developed in combination with sand property. The relationships among shear displacement，aperture and flow are discussed. It is proposed that the little distrubance of sand structure and the aperture change are primary affecting factors on fracture flow.

Based on the former simulation materials tests，some typical simulation materials are chosen to make models with hole. The rockburst simulation tests are made for rockmass with tunnel. During the testing process，the influences of loading conditions，mode of opening hole，geometry characteristic and other factors of rockburst are studied. The mechanism of rockburst is discussed and some conclusions are obtained.

Testing study and analysis are carried on EME characteristics and rules of sandstone，modstone and concrete under compressive and tensive states. The results show that the EME of sandstone，modstone and concrete can be produced under the loading. The EME of rock is of positive relevance with the load and memory effect. The biggest intensity of EME is of positive relevance with strength of rock during the loading process. The EME can be applied to determine intact rockmass stress，relative stress distribution of surrounding rockmasses，and evaluate the stress state and stability of coal and rocks.

The crack of the mining-disturbed rock strata affects the law of subsidence directly. But the existence of original joints in rock mass makes the crack complicated，so that the determination of subsidence range in rock mass becomes more difficult. The effects of original joints on the expanding law of crack of mining-disturbed rock strata，the range of the crack，the distribution of crack and effect of the subsidence range in rock mass are systematically studied. The influence of original joints on the crack of mining disturbed rock strata is analysed. The formula of the maximum tangent stress nearby original joints，the theory evidence to define the range of subsidence in rock mass and the mechanics condition of the crack of mining-disturbed rock strata are given. Four stimulated material models are made，which contains original joints with different distribution. The study result is well verified with the experimental data.

According to the features of roadway sub-level caving in steep seam，the factors influencing the stability of caving roadway are analyzed，and the model for selecting optimal support patterns and predicting stability of caving roadway is established based on improved BP neural metwork. The application of the model can provide scientific basis for support design of caving roadway and reliable guarantee for high product and high efficiency of roadway sub-level caving in steep seam. Application results show that the presented model with improved BP neural metwork is of high learning speed，good prediction precision and significant practical value.

Based on the parameter identification by inverse problem theory，neural network model is set up to model the constitutive relation for sandsoil，under different stress paths. The approach is different from the traditional ones. It can not only make full use of all information obtained from test data，but also reflect the effect of stress path，which is very important in numerial simulation for practical engineering.

The stability of slope is affected by many factors，which determine the specific shape，such as engineering geology，hydrogeologic condition and the activity of people (excavation or guard). However，it is difficult to find the definitive relationship among those factors and the specific shape. More than seventy times of landslides have happened in the unworking band of Haizhou mine since its foundation，and there more than sixty times of largescale ones were recorded in detail. Based on the abundant landslide data，the method of artificial neural network is used to describe the nonlinear relationship mentioned above. In the method，the input parameters include the friction angle and dip angle of the slide layer，the separation angle between the slide surface and slope trend，the length of the shear zone，rainfall，fault and the hight of the slope，while the output parameters include the length and width of gliding mass，and the distance between the crack and tip of the gliding mass. The result calculated by the network can be used to estimate the shape of other potential gliding mass only after the training of the network is completed. Then some effective measures can be taken to deal with the landslide，and also，the presented result can be used to validate the instability zone got in traditional ways.

Combining the GIS spatial analysis function with an improved Hovland 3D slope stability analysis mode，a new GIS based 3D deterministic model is developed. Assuming the initial slip as ellipsoid，the 3D critical slip surface is determined for the analysis of 3D slope stability by means of minimization of the 3D safety factors by using Monte-Carlo random simulation. In the analysis program，the analysis of slope stability can be easily processed and managed，and the results can be easily showed and reclassified on the spatial map.

Analysis is made on the landslide triggering factor susceptibility in Xiaojiang watershed，Yunnan by means of landslide certainty factor (CF). The presented results are helpful to study the landslide mechanism and spatial distribution characteristics. The factors contributing the landslide occurrence are determined，including lithology，structure，slope，elevation and faults，etc..

On the platform of GIS，the multi-factor spatial information analysis method and non-linear prediction method are combined. The statistics relationships among landslides and environmental factors are analyzed. The single factor analysis model，multi-factor analysis model，clustering analysis and non-linear prediction model are set up. On the basis of above research，the middle part of Lantau Island in Hong Kong is selected as experimental studying area，the dangerous landslide areas are predicted based on environmental factors. The map of regional landslide evaluation in the middle part of Lantau Island is obtained. The results show that the proposed model is of enough precision to offer important scientific basis for studying of dangerous areas of regional landslide and disasters of landslide.

A system of direct evaluation and aid design for artifical soil slopes stability is developed with VC++ 6.0. In the system，finite element method is used to evaluate the stability of slope. Decreasing the strength parameters，c and ，of soil in steps，the safety coefficient can be directly calculated in an iterative process using self-adaptation arc length control technique. The presented method can be used to visually simulate engineering design，such as digging，retaining wall，anchoring，by interactive computation. The system has been used to evaluate the stability of many slopes in China with satisfying results.

A simple and applicable calculation method is presented to analyse the subgrade stability in landslide areas. The process of calculation analysis is discussed in detail. Both calculation and analysis are made on different slide surfaces. The research results are of significance for fast analysis on the stability of cut slope.

The problem of determination of shear parameters (c，f ) for the intercalated beds of Xiluodu power station is discussed with 5 methods. The errors resulting from different methods are analysed. Comparison is made for the values of c and f obtained with different methods，so that the accuracy and reliability of c，f can be increased.

The south abutment slope of Renyi river great bridge is mainly made up of gypsum breccias. In order to quantitatively analyze the deformation，destruction and developing trend of the slope，9 soft rock samples were collected from the slope site. Then，normal triaxial compression testing，uniaxial and triaxial rheological compression testing were made. The samples were analyzed by thin section and electron microscope scansion before and after testing. Through above methods，the regularity of mechanical action，the characteristic of microfabric change of soft rock，and the effect of environment factors on the soft rocks are revealed.

The property of the rock mechanics and magnitude of differential subsidence value of foundation affect safety of buildings directly. On the basis of site regional geology，seismic geology and testing results of rock samples，the physico-mechanical parameters of country rocks are interpreted statistically. The standard values and design values of foundation bearing capacity，dynamic allowed bearing capacity and design values of earthquake-proof bearing capacity for foundation are given. The maximum and minimum values of foundation subsidence are calculated and the differential subsidence values of foundation are obtained. As a result，the reliable basis is provided for design and construction of nuclear power station.

The model testing is made on reinforced earth wall under repeated load of train to get the dynamic respond characteristics. The change regularity of the average values of acceleration and displacement are obtained with the height of the wall. The vibration equation of the reinforced earth wall under repeated load of train are also derived.

The grey system is the system in which some information is defined and some undefined. The in-situ stress field is a typical grey system. The grey model theory is used to analyse in-situ stress field. The obtained results are satisfying and the application of grey model theory to analysis of in-situ stress field is effective.

Now the equation of the relationship among various underground pressures applied in drilling engineering is not strict. Rock should be regarded as porous media. Based on this，the new equation is derived to include one important parameter of porous media，.

The formula of Terzaghi ultimate bearing capacity of foundation based on Mohr-Coulomb strength theory does not take the influence of intermediate principal stress into account. The influence of intermediate principal stress on the ultimate bearing capacity of foundation is researched based on twin shear strength theory. The ultimate bearing capacity of foundation will be increased when the influence of intermediate principal stress on the bearing capacity of foundation is considered.

Based on the complicated response of dilatancy of sand under cycle loading，the different physical states，including preliminary positive dilatation，secondary positive dilatation，negative dilatation，reverse positive dilatation and shear elasticity，are explored by the changes of effective stress path. Moreover，the physical states can be distinguished in the effective stress space by the stress history boundary and initial yield surface besides the state boundary and physical state transformation surface. A mathematic description is set up to express the changes of physical states by the moving law of the initial yield surface and history boundary.

Based on the construction process character of deep excavation，the method of back analysis and numerical simulation of dynamic deformation during construction process is set up by semi-analytical layer elements. Thus the values of the dynamic elastic moduli of soil layers are obtained. The deformations of wall and soil ground are predicted by use of the obtained values of elastic moduli of soil layers and are in good agreement with that of in-situ test.

A new stability analysis method——equal arc method(EAM) is presented. Based on this method，the soil upon the most dangerious slip plane is divided into a number of vertical soil-slices whose lengths of arc are equal. The safety factor of stability is a function of geotechnical parameters，retaining and protecting parameters，distribution of ground load，state of foundation pit excavation and circle-center-coordinates of the most dangerious slip plane. The visual software is developed and an engineering example is introduced.

According to the data of static loading test and dynamic high strain test of pile in Xining city，the bearing properties and loading transmission mechanism of the large-diameter and medium-long borehole cast-in-place piles in muddy rock foundation，as well as the influencing factors on its bearing properties are revealed by analyzing pile axis pressure transmission and soil resistance properties. The study result is instructive for design，construct and deep study of borehole cast-in-place piles in muddy rock foundation.