A Study on the Effect of Rock Discontinuities on Stress Wave Propagation and Dynamic Fracture

Rock discontinuities have a great influence on stress wave propagation. Nowadays, the influence of different filling states and filling material properties of rock discontinuities on stress wave propagation and dynamic fracture characteristic are unclear. The numerical models of rock mass with different discontinuities are established to study crack propagation under coupled static and dynamic loads, and the blasting failure process of coal mass with multi-group discontinuities is simulated. The results of stress analysis at each monitoring point and explosion damage analysis show that the reflection effect increased with the decrease of the mechanical properties of the filling material, and the transmission effect decreased with the decrease of the mechanical properties of the filling material. On the side of discontinuity with wave incidence, the “reflected stress waves induced cracks”, “layer-like cracks”, and “direction changed cracks” were formed due to the reflected stress waves, which aggravated the rock damage in this area. The transmitted stress waves can lead to the destruction of the discontinuities and the formation of macro-radial explosion cracks on the side of discontinuity without wave incidence. The number of main cracks formed in zone Ⅱ (the side with discontinuities) in models 2 ~ 5 (containing rock discontinuities) is about 60% ~ 75% higher than that in zone Ⅰ (the side without discontinuities), and the total length of explosion cracks in Model 3 is the largest. The numerical simulation results of coal rock explosion show that the discontinuities control the crack expansion and the explosion effect with increasing rock discontinuities. The research results can provide certain technical support for engineering blasting construction design, rock burst prevention and rock burst disaster.