Study on crack propagation mechanism and charge structure optimization of tunnel shaped charge hydraulic blasting

Explosive blasting in tunnel construction may provoke damage to the surrounding rocks, leading to economic and safety concerns. While studies on rock fragmentation mechanisms exist, the innovative mechanism of shaped charge hydrostatic blasting remains largely unexplored. This paper aims to fill this research gap by proposing the mechanical analysis model for shaped charge hydrostatic blasting. By integrating physical model tests with LS-DYNA numerical simulations, this study assesses the dynamic response and crack propagation behaviors of this blasting method compared to traditional shaped charge blasting. Further, this study delves into the effects of various charge structures on hole wall pressure and crack propagation characteristics in shaped charge hydrostatic blasting, finally determining the optimal charge structure. Findings reveal that the explosive stress of shaped charge hydraulic blasting persists over an extended period, effectively generating directional cracks. The water medium amplifies the near zone effect of blasting, curtails the disturbance in the far zone, augments the energy utilization rate of explosive, and enlarges both the crushing zone and the propagation of primary crack. The charge structure with water intervals at both ends of the energy accumulation device generally yields beneficial results, producing favorable directional cracks. However, the presence of water medium at the bottom of the blast hole impedes the rock fragmentation, it is advisable to increase the explosive quantity at this location.