Investigation of water-coupling presplit blasting considering the role of stress wave parameters

Abstract

Water medium has been widely used in decoupled charge blasting due to its high efficiency of energy transfer. In this study, water-coupling presplit blasting is investigated theoretically and numerically from the essential mechanism of the effect of stress wave parameters (peak pressure $P_b$, loading rate $L_r$ and attenuation coefficient $\alpha$) on presplitting. According to the propagation and superposition theory of stress waves, the inter-hole tangential stress peak distributions and hole spacings under different stress wave parameters are analytically given. Further, considering the role of stress wave parameters, water-coupling presplit blasting under different in-situ stresses ${\sigma }_s$ and delay intervals $\Delta t$ are investigated with air-coupling presplit blasting as a comparison. Through LS-DYNA, numerical simulations of presplit blasting are carried out to verify the reliability of theoretical analysis and further study their effects on the presplitting. Both the theoretical and numerical results show that the blasting load with higher $P_b$ and lower $L_r$, $\alpha$, ${\sigma }_s$ and $\Delta t$ favors presplitting. Under the same $P_b$, the stress superposition range, minimum stress peak and hole spacing of water-coupling presplit blasting are larger than those of air-coupling presplit blasting. The numerical results of the crack pattern also show that lower $L_r$ will change the crack pattern from the crushing zone extension dominated by compression-shear damage to the main crack propagation dominated by tensile damage, and the directionality of presplitting is more pronounced with higher $P_b$ and lower $L_r$, ${\sigma }_s$ and $\Delta t$. Compared with air medium, water medium has better performance in the directional effect of presplitting and anti-interference ability to the delay scatter due to its lower $L_r$.