Mechanical properties and mesoscopic analysis of rockbackfill-rock composite sample under dynamic loading

Abstract

During ore pillar excavation, the impact load of deep hole blasting does not act directly in the cemented paste backfill (CPB), which first acts within the ore pillar and then transfers the blast energy to the CPB and the adjacent ore. Therefore, it is a key issue to investigate the stability of the rock-backfill composite under dynamic loading. The paper prepared rock-backfill-rock (RBR) composite samples and conducted the Split Hopkinson Pressure Bar (SHPB) dynamic test with different impact amplitude. The dynamic uniaxial strength characteristics, mechanical characteristics, and failure modes of RBR composite samples under different impact velocities were analysed. The experimental results showed that the dynamic uniaxial compressive strength of the RBR sample increases first and then decreases with the increase of the average strain rate. With the rise in the average strain rate, the fragmentation degree of the RBR sample is deepened. According to the computerised tomography (CT) test results, the rock fails mainly in shear. Moreover, damage occurs at the interface between the CPB and the rock near the incident bar. It is primarily manifested as a ring-layered crack, resulting in its separation from the rock near the incident bar. The results of the study can further guide the stability of the backfill stope during the ore pillar extraction process.