Dynamic response and spalling of cemented tailings backfill under cyclic impact

Deep mining safety relies on the dynamic stability of cemented tailings backfill; however, its failure mechanisms in intricate loading scenarios are not yet well understood. This study utilized a split Hopkinson pressure bar apparatus to investigate the dynamic mechanical characteristics of this material, specifically contrasting its response under single and repeated impact loads. The results indicated that both compressive and tensile strengths exhibit a pronounced dependency on the strain rate. A significant contribution of this work is the identification of a unique spalling circumferential fracture pattern under cyclic impact loading for the first time, which stands in contrast to the axial splitting failure observed during single impacts. Numerical simulations further demonstrated that this unique failure mode arises from compression-induced plastic damage. Besides, while the energy absorption capacity exhibits strain-rate hardening, cyclic loading triggers a progressive degradation of energy dissipation efficiency. Compared to natural rocks, the backfill exhibits an enhanced peak stress under repeated impacts, particularly at lower loading rates. This research offers novel perspectives on the fracturing characteristics and rate-dependent behavior of cemented tailings backfill, contributing to the enhancement of safety protocols in deep mining engineering operations.