Effect of confining pressure on damage accumulation of rock under repeated blast loading

Abstract

In-situ stress has complex impacts on the blasting excavation of rock mass, but the effect of confining pressure on the crack propagation under repeated blast loading is still unclear. This study investigated the effect of confining pressure on blasting damage through theoretical, experimental and numerical analyses. First, the stress distribution around blasthole under static loading was theoretically analyzed. Then, the parameters of Riedel-Hiermaier-Thoma (RHT) model were determined and validated by repeated blast tests. The effect of confining pressure on the failure mode of granite sample was included. Finally, pre-split blasting of rock slope was numerically simulated to explore the failure behaviors of rock mass under in-situ stress conditions. The numerical results indicate that the RHT model can well reproduce the tensile failure behavior and dynamic crack propagation of granite sample. Confining pressure significantly changes the failure mode of granite sample and the blast-induced cracks mainly propagate along the direction of maximum principal stress. Repeated blast loading has little contribution to rock breakage in the direction of minimum principal stress. The pre-split blasting technology can considerably improve the stability of remaining rock mass in the blasting excavation of rock slope. A plum-blossom-shape arrangement of blastholes and delayed initiation of production holes can promote the quality of blasting operations under pre-stress conditions.