Study of deformation and failure in an anisotropic rock with a three-dimensional discrete element model

Abstract

This paper is devoted to numerical analysis of deformation and failure of transversely isotropic rocks. A three-dimensional discrete element (DEM) model is proposed in the framework of the particle flow code (PFC). The anisotropic rocks are characterized by a matrix phase in which non-persistent weak layers are embedded. The mechanical behavior of the matrix is described by a non-linear bond contact model while that of weak layers by a smooth joint contact model. The local elastic and strength properties in the bond and smooth joint models are calibrated from the corresponding macroscopic properties. Numerical predictions are compared with experimental data obtained from triaxial compression tests performed on a clayey rock, Tournemire shale. The anisotropic behavior of both elastic modulus and failure strength is well reproduced. The influence of confining stress on the failure strength of shale rock is also captured. A series of three dimensional numerical simulations are further performed for different orientations of weak layers and confining stresses. The effect of weak layers and confining stress on both local cracking process and macroscopic failure mode of rock samples is investigated and discussed.