Study on blast pile distribution characteristics of bench blasting under hole-by-hole initiation

To investigate the rock fragmentation process and the distribution patterns of the blast pile in bench blasting under hole-by-hole initiation, the rock-breaking effect of spherical charges was analyzed based on the theory of rock blasting zoning and the formation process of the blasting crater. By using the discrete element software PFC, a reasonable numerical model was constructed. Combined with field construction data, the distribution characteristics of the blast pile by bench blasting and the movement patterns of oversized fragments were studied. The results show that rock located at the bench slope and the top of the bench is prone to form oversized fragments due to insufficient rock-breaking energy; these oversized fragments are mostly distributed at the bottom of the blast pile and the edges of the blast area. The blasting action of the front-row holes provides sufficient free surfaces for the rear-row holes, facilitating the reflection and tension of explosive stress waves at the free surfaces, thereby improving rock-breaking efficiency. Oversized fragments at the bottom of the blast pile are mainly generated by insufficient fragmentation of the rock mass at the base of the bench, which explains why oversized fragments are predominantly concentrated at the bottom of the final blast pile. Overall, the numerical simulation results show a high degree of agreement with the actual blasting results.