Effect of pre-existing flaws on spalling fracture of granite

The intact and pre-existing flaw granite specimens were tested by using the split Hopkinson pressure bar device with 50 mm rod diameter, and the whole process of spalling fracture was recorded by a high-speed video camera. Based on the theoretical analysis, the possible initial spalling positions of the granite specimens under half sine wave loading were calculated. The results of high-speed photography show that the pre-existing flaws have certain influence on the initial spalling positions, and spalling fractures generally occur at pre-existing flaws. According to the PFC2D (particle flow code in two dimensions) model, it is found that the initial spalling positions are influenced by the pre-existing flaws and the rising edge of the reflected tensile wave. The longer the rising edge of the reflection wave, the more likely the initial spalling occurs at the pre-existing flaw. The shorter the rising edge of the reflected tensile wave, the less likely the initial spalling occurs at the pre-existing flaw.