Key blasting parameters for deep-hole excavation in an underground tunnel of phosphorite mine

Abstract

Ever increasing mine production capacity and mechanized operations enable advanced drilling equipment to be widely adopted in underground mines. In order to achieve satisfactory blasting performance in tunnel advance, there is a critical need to optimize the blasting technique to match the large deep-hole drilling capability. In this study, through theoretical analysis of tunnel blasting, the layout of cutting holes was found to be the key factor controlling the blasting performance. The deep-hole cutting effect was first investigated by analyzing the influence of the free surface of a hollow hole using the fluid-structure interaction modeling method in ANSYS/LS-DYNA. Then the rock dynamic evolution processes of blasting using a double-cavity grooving and a four-cavity grooving were compared and analyzed towards an understanding of the influence of the spacing and layout of cutting holes on the blasting performance. The comparison results show that four empty hole cut layouts yield larger effective free surface than that of the two empty hole cut layouts. This is because larger compensation space for breaking of rock and expansion of gas is more conducive to improving the energy utilization rate of explosives and thus improving the blasting performance and the footage of cyclic blasting. The results indicated that the blasting performance can be improved by reserving reasonable compensation space in the grooving area.