Based on the discrete particle model，which is used to solve the solid phase and to obtain the individual grain¢s information such as location，velocities and displacements，etc.，Darcy seepage model for the analysis of fluid-solid interaction in granular materials with interstitial water is proposed. Combined with the characteristic based smoothed particle hydrodynamics(SPH) method that is used to get Darcy¢s velocities，the numerical solution scheme for the seepage model of saturated and unsaturated granular materials is presented. Numerical results demonstrate the capability and good performance of the proposed model in modelling the fluid-solid interaction and deformation in granular materials with interstitial water.

Because of the suspects on the theory of unloading rebound，three experiments are performed；and it is noticed that some interesting phenomena that are not understood previously are discovered. Based on the observed phenomena，a hypothesis on the original state of strain energy in a geological body after diagenesis，which is different from present theories，is advanced. On the hypothesis，there is no strain energy in a geological body after diagenesis unless other external forces act on it. This new hypothesis gives a possible reason for the surface subsidence around an open pit. The constitutive equation by which the behavior of the cast material body is characterized in one of the three experiments is established. A new computer program is developed；and it is employed in trial examples of simulation of displacement fields from excavation；and satisfactory results are obtained. The achieved results agree well with in-situ measurements in direction of displacement vectors as well as in relative magnitude. The question when a geological body after tectonic movement(s) is excavated，is discussed，whether or not its original state of strain energy will cause up-rebound strain.

Circular sample window method is not applicable for joint surveying in field. A uniform data structure is designed for joint data of all trace types. The joint trace map is drawn according to field surveying data，and circular sample windows are arranged on the joint trace map. The position，quantity and radius of the circular windows are adjusted to the specific conditions of surveying data. Simultaneously，the quantity of different trace types in the same circle is identified and recorded. Based on the circular sample window method theory，the trace midpoint density of joint is obtained to estimate the mean trace length. The distribution of the trace midpoint is not uniform，and it is far from being insignificant for reasonable results that position and radius of circular sample window are selected appropriately. Concentric circle method and tangent circle method are applied to estimating the mean trace length and the trace midpoint density in Jiji quarry. It indicates that tangent circle method is stable and reasonable. The joint data，which are surveyed in the candidate region of high radioactive waste in Beishan Mount，Gansu Province，China，are analyzed with tangent circle method. As a result，the influence range of the fault is concluded by analyzing the mean trace length and the trace midpoint density of joint on the both sides of the fault.

Slate is a common geological material in geotechnical engineering. Traversed by joints and schistosities with clay minerals，the mechanical characteristics of slate are complex；and the existence of the numerous microscopic cracks and voids aggravates the complexity. Using the loading equipment corresponding CT machine，the CT real-time tests of two unsaturated jointed slate samples from Jinping-II Hydropower Station under triaxial compression are conducted. The typical CT images in failure process are obtained. With the obtained CT images，the evolution processes of crack initiation，propagation，coalescence，and finally macroscopic fracture formation are analyzed in the microscopic scale；and the differences of failure mechanisms with different strata distributions are explained. Based on the principle of CT，the scalar damage variants of unsaturated rocks are presented with the CT values.

The strength reduction method(SRM) is mainly used for two-dimensional slope stability analysis. In order to verify its feasibility for the stability analysis of three-dimensional issues，two benchmark problems，i.e. planar slide and wedge slide，are selected；and the safety factors are calculated by SRM. The obtained safety factors agree well to the analytical solutions by E. Hoek and J. W. Brown；and the modeled sliding direction is also almost the same as the hypothetical one. In the analysis，solid elements are used to model the behavior of structural planes，so the influences of their thickness and element intensity on modeling precision are further investigated. For blocks cut by planar structural planes，the influence is limited when the thickness is 1/10–1/200 of the block height. Compared with the displacement criterion of characteristic points，the entirely run-through criterion of plastic zone is more rational for its theoretical coherence to the theory of limit equilibrium and its easy use in application. The stability of a pentahedron block is further analyzed to verify the applicability of the method.

Based on the principle of information spread，normal information spread estimation method(NISEM) is proposed to generate probability density functions of geotechnical parameters with small samples. The new method is distribution-free for no classical theoretical distributions were assumed in advance；and the inference result provides a universal form of probability curves. Then it presented a good solid mathematical and physical performance. Kolmogorov-Smirnov test is used to verify the availability of this method. The results of case study show that the index Dn in NISEM is all smaller than those in the classical finite comparative method(FCM)；and the NISPM function is more accurate and effective than FCM. It shows that the presented method can be used in stochastic reliability analysis of geotechnical engineering.