ABSTRACT:

Deformation and failure mechanism of rock masses are governed by the characteristics of geometrical distribution of discontinuities and the mechanical behavior in a single discontinuity. It is thought that stability of rock structures extremely depend on not only the existing discontinuities but also new cracks, which are generated and progress due to loading or excavation. This study presents a new function describing the mechanical behavior of discontinuities. The formulation is based on the results of laboratory shear tests with the aim at modeling the shear behavior at variant normal stress levels. The rational approach is also proposed to define the generation and progress of the potential cracks due to shear and tension failure in the matrix by using distinct element method (DEM). Simulation of a deep underground opening excavation in the discontinuous rock masses is carried out and discussed on the deformational behavior and stability of the surrounding rock masses.

INTRODUCTION

While analyzing, designing and predicting the performance of engineered structures built in and around jointed rock mass, it is essential to have a good understanding of the mechanical behavior of the rock mass under imposed boundary conditions. A rock mass of a site is not continuum and its behavior is dominated by the existing discontinuities such as bedding, joints, faults and fractures. Presence or absence of these discontinuities has a very important influence upon the stability of engineering structures and therefore, these geological features have to be taken into consideration properly for practical designs. Stability analysis of rock structures such as rock slopes, foundation and underground openings can be carried out by the finite number method (FEM) and the distinct element method (DEM). The FEM, however, uses continuous formulation and is therefore not suitable to simulate the progressive failure accompanied with large deformation in rock masses.

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