Numerical modelling of the response of cemented paste backfill under the blasting of an adjacent ore stope

Abstract

An in-depth understanding of the response of backfilled stopes during the blast excavation of adjacent ore stopes is crucial for the effective backfill design to improve workplace safety and ore recovery. In this study, numerical simulations are performed to explore the effects of blasting schemes and ratios of cement to tailings (c/t) on the responses of cemented paste backfilled stopes under blasting in adjacent ore stopes. Three-dimensional models comprised of ore stope, backfilled stope, explosive charge, and air were numerically established. The ore stope and backfilled stope were discretised by finite elements, while explosive charge and air were explicitly modelled using a particle-based approach. Three blasting schemes, including detonating the blastholes simultaneously, detonating the blastholes row-by-row, and detonating the blastholes column-by-column, were carried out in the ore stope, and four c/t ratios, i.e., 1:4, 1:6, 1:8, and 1:10, were used in the backfilled stope. The versatile Karagozian and Case concrete (KCC) constitutive model was used to describe the mechanical behaviour of ore and backfill materials. Its input parameters for cemented paste backfill samples with different c/t ratios were calibrated based on the uniaxial compression and Brazilian tensile testing results. The numerical results show that the row-by-row, column-by-column, and simultaneous blasting scenarios produce a similar breaking performance in the ore stope, but the latter induces the minimum damage volume in the backfilled stope. The damage generated in the backfilled stope induced by the blasting excavation in the ore stope decreases as the c/t ratio decreases. It is also found that the layered backfill structure lowers the cement cost and improves the blast resistance, and its damage tends to concentrate in the layers with higher c/t ratios. The results obtained here highlight the importance of the ductile behaviour of cemented paste backfill in the blasting resistance performance of backfilled stopes.