Dynamic damage characteristics of rock under multiple loads during high-voltage pulse fragmentation

To analyze the damage characteristics of rocks during high-voltage pulse fragmentation (HVPF), two kinds of loads, shockwave and cavity, are determined by optical observation, and the pressure–time characteristics of these two and their mechanism of damage to rocks in mesoscopic view are analyzed. A model of dynamic damage characteristics of brittle rock under multiple loads is established, which includes numerical calculation and discrete element simulation. In the discrete element simulation, the rock is simplified as a circular region without reflection boundary with a certain size of the circular hole inside, and the grains in the region are discretized as rigid spheres with a definite bonding relationship. The shockwave is considered the time-varying pressure loaded to the grains of the circular hole, and the cavity is considered the quasi-static pressure loaded to the grains on both sides of the fracture. The results of the model show that shear cracks and tensile cracks are produced during the shockwave action, but tensile cracks are predominant. The shockwave acts as a preload for the expansion of cracks, and the damage radius is small. Most of the cracks in HVPF are caused by the cavity. A comparison of the numerical calculation results with the discrete element simulation results shows that the model can describe the distribution characteristics of cracks under multiple loads, which lays a foundation for further analysis of the internal mechanism of HVPF.