Theoretical Models for the Borehole Pressure of Air-Decoupled Charge with Discontinuous Interface Conditions

The borehole pressure of the rock mass under blasting under consideration is essentially the pressure of the transmitted shock wave acting on the borehole wall. Its value directly affects the fragmentation degree and damage range of the rock mass around the borehole. The whole-process action mechanism of the shock wave in different media and interfaces for air-decoupled charge explosion was comprehensively analyzed, discontinuous Galerkin (DG) method was used to simulate and solve parameters of the multiple media flow field formed by the detonation products and air in the borehole. Two theoretical calculation models of the borehole pressure of air-decoupled charge with discontinuous interface conditions of the pressure and particle velocity were proposed and their algorithm flows were presented. Furthermore, the reliability and feasibility of the proposed models were verified by comparing with the numerical simulation results of the same example under five working conditions. It is suggested to use different theoretical models when using different decoupling coefficients. It is shown that there is an optimal value of the decoupling coefficient for air-decoupled charge, which makes the rock blasting obtain a high utilization rate of explosive energy and good blasting effect at the same time. This study can provide a theoretical basis for revealing the blasting rock-breaking mechanism and optimizing blasting designs.