Three-dimensional nonlinear strength criterion for rock-like materials based on the micromechanical method

In this paper, it is assumed the rock-like materials contain penny-shaped microcracks. The modes II and III stress intensity factors at tips of the three-dimensional penny-shaped microcracks are determined. The micro-failure orientation angle α is given out to describe the failure of rock-like materials. The formulation between the micro-failure orientation angle α and stress components is obtained from the mixed-mode fracture criterion. Failure characteristic parameters under true triaxial compression condition are defined, which are an invariant and are relative to the intermediate and minimum principal stresses. A three-dimensional nonlinear strength criterion of rock-like materials, in which the effects of the intermediate principal stress on the failure of rock-like materials is taken into account, is developed based on micromechanical methods. The theoretical nonlinear strength criterion is novel, which is not found in the previous references. By comparison with experimental data, it is shown that the present theoretical strength criterion is in good agreement with the experimental results.