Discrete element study on the mechanical behavior of flawed rocks under dynamic compression

Abstract

Pre-existing discontinuities in rock engineering significantly affect the entire structural stability, especially when subjected to dynamic loads. To deepen the understanding of fracture mechanism of flawed rock specimens, a numerical study based on the discrete element model was conducted to investigate the effects of flaw geometry and strain rate. The results indicate that the dynamic strength is sensitive to the flaw length, flaw inclination angle and strain rate. Their effects on the fracture process and failure pattern were also numerically revealed by acoustic emission and micro crack monitoring. The numerical results well reproduce the experimental results. A method combining displacement vector field, micro crack distribution and force chain pattern was proposed and it can effectively identify the crack type from both macro and micro perspectives. In accordance with the particle velocity difference, it is found that the crack initiation position moves from the flaw center to flaw tips with the inclination angle increasing, and only the flaw length longer than the critical value can affect the fracture behavior. In addition, the cumulative microcrack length can somewhat represent the fragmentation of the flawed specimen after final failure.