Influence of delay time on the blasting effect of multiple charging forms in single free face rock mass

This article takes coal mine rock roadway blasting excavation as the background to explore the influence of delay time on the blasting effect of different charging structures under single free surface conditions. Firstly, single pore dispersed charge models, dual pore continuous charge models, and dual pore composite charge models were established, and their respective explosive rock breaking mechanisms were explained through different models. Secondly, the above three numerical model were established to analyze the influence of delay time changes on the pressure and velocity of measurement points near the borehole. The blasting effects of different models were evaluated by throwing out the number of free surface rocks. Finally, the above research was validated through engineering experiments. Findings indicate that single hole dispersed charge create a cavity and a new free surface, which has a more significant effect on improving the effect of deep hole blasting than stress wave superposition. The difficulty of dual hole continuous charge detonation is high, and short delay detonation can effectively utilize stress wave superposition and prolong the action time of explosive gas. The key to improving the efficiency of dual hole composite charge blasting lies in fully utilizing the cavities created by dispersed charges.