ABSTRACT:

A Homogenized Multi-Crack Model is proposed in order to estimate the deformability of a rock mass which has a high crack density. In this model, all cracks are parallel and infinitely arranged at equal intervals in all directions, and the crack pattern around a crack is always the same at any part of the model. In this study, the effective compliance of HMCM is estimated by applying the 2-Dimensional Displacement Discontinuity Method and linear fracture mechanics. It was found that the deformability of the model in the direction normal to the cracks is strongly affected by crack length, crack intervals in the normal direction of cracks and crack patterns.

INTRODUCTION

The deformation and failure of a rock mass is largely dependent on the presence of geological discontinuities such as cracks or faults. In the case of high crack density the mechanical properties of the rock mass, such as compliance or Young's modulus, are strongly affected by the mechanical interaction between the cracks, and therefore a quantitative evaluation of this interaction is necessary (Anderson, 1974; Walsh 1974; Kaneko, 1990). However, there are few studies about these basic problems, especially in the compressive stress field or mixed mode loading problem. Here, a Homogenized Multi-Crack Model (HMCM) is proposed in order to estimate the deformability of a rock mass which has a high crack density. In HMCM, all cracks are parallel and infinitely arranged at equal intervals in all directions, and the crack pattern around a given crack is always the same at any part of the model. In this study, the effective compliance of HMCM is estimated by applying the 2-Dimensional Displacement Discontinuity Method (2D-DDM) (Crouch, 1983) and linear fracture mechanics. The influence of the mechanical interaction of each crack towards the effective compliance is also discussed.

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