A micromechanics-based elastoplastic damage model for quasi-brittle rocks

This paper presents a micromechanics-based elastoplastic damage model for quasi-brittle rocks in compression stress state. The plastic strain is considered to be related to frictional sliding along microcracks and inherently coupled with damage evolution. By following a homogenization procedure, we first determine the free energy for the matrix-cracks system. The thermodynamic force associated with the inelastic strain contains a back stress which controls material hardening. Next, a Coulomb-type friction criterion serving as plastic yielding function and a strain energy release rate based damage criterion are proposed for determination of plastic flow and crack propagation. These micro-macro thermodynamic formulations allow to reducing significantly model’s parameters with respect to phenomenological models. The proposed model is applied to simulate triaxial compression tests on two sets of diabase samples, the first cored from a fresh diabase rock mass and the second from a slightly weathered one. Comparisons between numerical predictions and test data are presented.