Numerical study of dynamic fracture behaviors of rock containing double pre-existing flaws under different confined stress and flaw geometry

In underground rock engineering, flaws can significantly affect both the physical properties and mechanical properties of the rock. The dynamic failure mechanism of sandstone with double pre-existing flaws is systematically analyzed through the parallel bond model in particle flow code. First, the model of the intact sandstone sample is established to verify the rationality of the parameters. Simulations of dynamic compression are then performed on sandstone that contains double pre-existing flaws under different impact velocities and confining pressures. The research results show that sandstone samples with various flaw lengths, rock bridge lengths, rock bridge angles and flaw angles exhibit different failure modes, strength reduction and AE evolution characteristics. Furthermore, by analyzing microforce fields, the cracking type and the crack propagation mechanism of sandstone samples are revealed. The rock bridge angle has a significant impact on the propagation of microcracks and the dynamic failure of the rock mass; while the rock bridge length between the two flaws has little effect on this.