The law of blast stress wave propagation and fracture development in soft and hard composite rock

Abstract

The process of blasting stress wave propagation and crack propagation is directly affected by the physical properties of the rock mass and internal joints in the rock. In soft and hard rock layers, the blasting process is more complicated due to the blasting stress wave needs to penetrate two kinds of rocks with different physical properties and the interface between soft and hard rock. This study analyzed the modal transformation of stress waves at the interface of composite stratified rock and the process was reproduced by finite element analysis. Further, development law of cracks was also been studied. The research results show that: In the single blasting-hole model, a triangular crack area caused by reflected stress waves appears at the rock interface of rock medium I near the blast hole. In the rock medium II, the tensile crack generated by the interface wave appeared on the side away from the blast hole. And the development of the tensile crack is related to the incident mode of the blast stress wave and the incident angle. In the deep hole blasting model, the incidence of the detonation wave front from hard rock to soft rock promote to the fragmentation of the hard rock.