Progressive failure mechanisms in jointed rock: insight from 3D DEM modelling

Abstract

Instabilities occurring in rock masses are generally related to the presence of preexisting discontinuities and the destabilization process often related to the complex interaction between the discontinuities and the rock matrix through the progressive breakage of rock bridges. A 3D model for fractured rock is presented here. The model uses a discrete representation of the intact medium over which discontinuity planes can be overlaid to represent predefined DFNs representative of pre-existing geological structures. These structures, or joints, can then be simulated using a modified contact logic where interactions are setup depending on the orientations and mechanical properties of the joint surfaces. Uniaxial compression tests on a pre-flawed sample are simulated in order to emphasize the relevance of the model in reproducing the so-called “wing crack” extensions usually observed around penny shaped cracks. The model capabilities in terms of crack propagation and coalescence are then discussed on the basis of simulations performed at the scale of a jointed rock slope, with an emphasis on its capability to reproduce one of the key mechanisms usually involved in the development of progressive failure surfaces, the so-called step-path failure mode.