Modelling progressive failure in fractured rock masses using a 3D discrete element method

Abstract

Instabilities in rock structures involve coupled mechanisms related to both deformations along existing discontinuities and brittle fracture of intact rock. Conventional kinematic and limit equilibrium techniques used to study rock slope stability suffer from oversimplifications. Mass strength degradation and progressive failure mechanisms in rock bridges cannot be ignored and must be considered to predict the overall slope behaviour. A 3D numerical model based on the discrete element method has been developed to overcome these limitations. Pre-existing discontinuities as a Discrete Fracture network (DFN) can be initially plugged into a set of discrete elements combined with the use of a modified contact logic which provides an explicit representation of joints. Both fracturing of intact material and yielding within discontinuities can therefore be reproduced, depending on the loading conditions and material strength. Simulations of referenced experimental tests are presented here to show the capabilities of the model in tackling the failure mechanisms of intact rock in the presence of pre-existing discrete fractures, with an emphasis on the initiation and propagation processes. This model proves to be a promising tool in understanding and predicting instabilities that could lead to the failure of fractured rock slopes.