Mechanism study of preventing crack propagation of fractured rockunder dynamic loads

Abstract

To deeply understanding dynamic fracture properties and preventing crack propagation of fractured rock mass under dynamic loads, impact experiments were conducted using TWSRC (tunnel with single radial crack) samples, and sandstone were selected as the raw material to manufacture fractured rock samples. The crack initiation, propagation and obstructing behavior were measured by using a drop hammer impact test device and crack propagation gauge measuring system. The mechanism of preventing crack propagation and failure behavior during dynamic fracturing process was focused, and then the corresponding numerical simulation was conducted by using the finite difference code, which can be used to accurately estimate the experiment result. The results indicate that the whole dynamic fracturing process of fractured rock under dynamic loads is composed of the cyclic process of crack initiation, high-speed crack propagation, slowly deceleration, preventing crack propagation. In addition, the period of crack obstruction was approximate the microsecond level. The ratio of transgranular (TG) fracture at the crack obstruction point of fractured rock was smaller than that of the crack initiation point, and the ratio of TG fracture of green sandstone during the dynamic fracturing process was larger than that of black sandstone. The fracture energy for crack initiation again after crack obstruction was much less than the fracture energy required for the initial initiation of pre-existing crack.