Moldeling Of Failure And Hydro-Mechanical Coupling In Fractured Rock Mass

Estimation of hydro-mechanical coupling effects is very essential in many rock engineering projects, such as geological repository of wastes, high and steep rock slopes and underground hydropower houses. However, due to the presence of discontinuities, both hydraulic and mechanical properties of rock masses are difficult to characterize. In situ experiments are either expensive or impossible, making numerical modeling an inevitable way for characterization of rock mass behaviors.In this thesis, a unified hydro-mechanical coupling model based on the discrete fracture network mode (DFN) and the improved rigid body spring method (RBSM) is proposed for both intact rock and fracture network. Specifically, the main contributions are listed as follows.(1) A meso-scopic model for simulation of rock failure is proposed based on the improved rigid body spring method. In this model, the micro structures of rock mass such as pre-existing fracture network are explicitly considered and the whole process of initiation, propagation and coalescence of new cracks is can be simulated as well. The intact rock is represented by large numbers of uniformly distributed rigid blocks connected with each other by springs. Macro deformation is reflected by the local deformation of common interfaces between blocks.(2) A dual porosity model for seepage flow in rock mass is proposed based on the discrete fracture network model. Combined with the improved rigid body spring method, the permeability variation during rock failure is investigated.(3) A VI formulation for seepage problem with free surface is extended to fracture networks both in2-D and3-D space. This formulation is adapt to solve free surface problems in fracture network even with very complex topology and boundaries such as drainage tunnels.(4) For densely fractured rock mass, the deformability and conductivity of intact rock is neglected. A non-linear fracture constitutive model is introduced to take into account the non-linear normal stress and deformation relationship, tangential shear slip and dilation effects. The controlling mechanisms of hydro-mechanical coupling under different stress conditions are detected.