Numerical Investigation of Blast-Induced Rock Movement Characteristics in Open-Pit Bench Blasting Using Bonded-Particle Method

Blast-induced rock movement (BIRM) may lead to large ore loss and dilution in many mines using the pre-blast ore boundary to guide shovel loading. In this study, a simulation approach consisting of the finite element method for blast loading calculation and the bonded-particle method for bench blasting simulation was applied to study the BIRM. First, reasonable micro-mechanical parameters, equivalent blast loading and wave velocity were obtained. Then, particle velocity distribution, accumulation process and BIRM characteristics for single-hole and four-hole bench blasting were recorded and analyzed. Last, the effect of burden and bench height on BIRM were illustrated. After identifying the bench model using colorful rock strips, the obtained results show that the rock strip far from the bench face shows a fold-back stacking phenomenon, and blast-induced rock movement distance (BIRMD) first increases and then decreases from the bench floor to the blasthole bottom while the extreme BIRMD occurs at the bottom of stemming section. Next, the rock strips near the bench face may form a state of forwarding flapping due to the naturally accumulation under gravity. After analyzing the horizontal BIRM distribution and defining the mean horizontal rock movement (MHRM), BIRM becomes obvious with the increasing bench height, decreasing burden, and the decreasing distance from the bench face to particle. In addition, the obtained numerical results were verified using theoretically calculated maximum throw distance, BIRM measurement results and actual muckpile profile.