Numerical study of the influence of loading rate on fracture mechanism in elastoplastic rock-like materials with a modified phase-field model

The failure mode in rock engineering structures is closely related to the loading mode and loading rate, because of the inertial effects under a wide range of geological conditions. In this work, we propose a modified framework of the phase-field model coupled with plasticity, to investigate the effects of loading rates on the fracture mechanism in elastoplastic rock-like materials. By means of this framework, the damage-plasticity coupling effects on the mechanical responses and failure mode are also studied with an optimized pressure-sensitive plasticity model. The capability and accuracy of the proposed phase-field approach in capturing the nonlocal damage evolution is validated based on the elastic/inelastic homogeneous case with analytical solutions. Then the mixed-mode cracking behavior of the representative numerical examples are demonstrated under quasi-static and dynamic loading conditions from low to high loading rates. The failure modes, dynamic damage profiles and the crack propagation velocities in the examples with various loading rates were captured. Numerical results are discussed with comparison to previous experimental observations and available numerical works.