Burden is one of the main parameters in blast design. However, field tests, either single- or multi-hole blasts, used to determine an appropriate burden, are difficult to capture crack propagation, evolution of breakage angle, and the mechanism governing these processes in the rock. In this study, a single-hole bench blasting model is developed using LS-DYNA software to comprehensively investigate the relationship between burden and rock breakage. The simulation results show that the breakage angle decreases with the increase in burden, and the blasted volume reaches a peak value with a burden of 4 m. Meanwhile, backbreak distance increases with increasing burden. The optimum burden in this simulation is found to be 4.0 m, as the ratio of burden to blasthole diameter is equal to 20.62 and the ratio of burden to bench height is 0.44, based on a comprehensive analysis of the blasted volume, average damage, and total damage. Under the optimum burden condition, tensile stress wave regions are simultaneously generated at the free surfaces of both the bench top and bench slope, allowing more effective utilization of the two free surfaces and resulting in a more uniform damage distribution within the burden region.
Rong et al. (Thu,) studied this question.