Abstract
The crack propagation process may cause connecting the main fractures and discontinuities to break away the rock slopes and produce large-scale failures in rock masses surrounding large surface mines. In this research, the pattern of cracks propagation and coalescence in jointed rock slopes under in situ stress conditions is modeled using a higher-order indirect boundary element method (known as displacement discontinuity method). The linear elastic fracture mechanics (LEFM) principles are assumed for brittle rock mass, and a mixed mode fracture criterion known as the maximum tangential stress criterion is implemented in a higher order boundary element code (programmed in Mathematica).Prediction of the fracture mode, crack initiation angle, cracks trajectory and cracks coalescence within the rock bridge area of rock slopes can simultaneously be accomplished via this modeling technique. In the case of crack’s conjunctions and block creation, the results obtained can effectively be coupled with the discrete element method (DEM) (i.e. the universal distinct element code (UDEC)) to predict the blocks movements and shear displacements on newly connected discontinuities (high stress concentration points or plastic zones).
1. INTRODUCTION
Nowadays, application of rock mechanics and fracture mechanics principles in rock slope engineering problems is an interesting subject for researchers and rock slope engineers in order to improve the methods of stability analysis and safety factor determination. For instance, the safety factor for 25 sites of small rock slopes containing single isolated crack and edge crack under mixed mode I/II loading were computed using fracture mechanics fundamentals and limit equilibrium analysis. Their results were generally in good agreement with the field observations which may be reasonable for rock slope stability analysis [1]. In the similar case, stability of a small rock slope containing single cracks was analyzed based on the fracture mechanics approach and finite element method (FEM) under the effect of nonuniform stress distribution. Results from scrutiny of three slopes containing single cracks in mode I, mode II and mixed mode I/II of loading have indicated that the stable height of a slope may be estimated given the crack length in the slope [2]. Additionally, a complex procedure of arrayed discontinuities extension in a vertical slope was investigated using displacement discontinuity method (DDM) [3]. Cai et al. surveyed the tensile crack propagation in vertical slopes using FEM and strain energy density criterion. By so doing, the strain energy density factors were calculated in order to determine the critical heights of the slopes under the effects of tensile crack extension [4].
