Three-Dimensional Nonlinear Dynamic Strength Criterion for Rock

It is assumed that rocks contain three-dimensional (3D) penny-shaped microcracks. The Mode II and III dynamic stress-intensity factors at the tips of 3D penny-shaped microcracks are determined. The orientation angle of microfailure in rock materials is obtained to describe the dynamic failure of rocks. The relationship between the microfailure orientation angle and stress components is derived from the dynamic fracture criterion. Failure-characteristic parameters of penny-shaped microcracks under dynamic triaxial compressive condition are defined; these are an invariant. A 3D nonlinear dynamic strength criterion of rocks is established using the micromechanical method. The 3D nonlinear strength criterion is novel, and is not found in the existing literature. By comparison with experimental data, it is shown that the present 3D dynamic strength criterion is in good agreement with the experimental results.