Influence of material heterogeneity on failure intensity in unstable rock failure

Unstable failure of brittle rocks is a hazardous problem in deep mining and tunneling projects. Failure of brittle rocks around excavation boundaries is dominated by tensile fracturing. Homogeneous models cannot capture this rock failure mechanism while heterogeneous models are proven capable of capturing it. A question that may arise is how a change in failure mechanism influences the failure intensity. In this paper, an explicit FEM tool (Abaqus) is employed to simulate failure of homogeneous and heterogeneous rocks. Material heterogeneity is introduced into Abaqus models using Python scripts and the simulation results demonstrate that heterogeneous models can capture splitting rock failure. The effect of material heterogeneity on rock failure intensity in unconfined and confined compression tests is investigated. The simulation results from both types of models show that rock failure is more violent when the loading system is softer and the confinement is lower. However, it is observed that when two materials have the same peak strength, the heterogeneous model has more released energy than the homogeneous model due to the difference in the failure mode. The tensile splitting failure mode of the heterogeneous model releases more energy than the shear failure mode of the homogeneous model. This can be an important point to be considered for rockburst support design. Furthermore, the simulation results show that for two models with similar material composition, the strength of the more heterogeneous model is lower than the less heterogeneous model; as a result, the failure of the more heterogeneous model will be less violent if it fails in an unstable fashion, and this is in good agreement with field observation results.