Deep Rock Blasting Using Decoupled Charge with Different Coupling Mediums

Blasts using decoupled charge with various coupling mediums are extensively operated in underground excavation, and blasting challenges are always encountered in deep rock mass due to the influence of high in-situ stress. In the present study, the dynamic responses of deep rock mass in blasting with decoupled charge and different coupling mediums (air, dry sand, wet sand, and water) are theoretically and numerically investigated. First, the transmission, propagation, and superposition of stress induced by blasting coupled with different coupling materials, and the effect of static stress distribution around boreholes on the crack initiation and propagation in blasting under conditions of varying hydrostatic pressure and anisotropic in-situ stress are theoretically analyzed with a two-hole planar analytical model. Then, a numerical model is constructed and verified against the rock fracture network obtained from a blasting test. Based on the verified numerical model, two-hole planar computational models with the same configuration as the analytical model are developed and used to perform a series of simulations. The joint effect of the coupling medium and the in-situ stress on the initiation, propagation, and interconnection of blast-induced cracks are numerically analyzed and interpreted by combining with theoretical results. The analytical and numerical investigations indicate that the evolution of blast-induced cracks in deep rock mass is mainly controlled by the stress transmitting from explosive to rock, superposition of explosion stress waves, as well as the magnitude and orientation of in-situ stress. Finally, the implications of current findings for practical blasting in deep rock mass are discussed. This study develops the understanding of rock cracking induced by blasting with different coupling mediums under high in-situ stress and provides some guidance to solve blasting difficulties in deep rock mass.