Crack propagation and distribution characteristics of deep-buried rock masses under water-coupled presplit blasting

Abstract

In deep rock blasting excavation, high in-situ stress often leads to difficulties in presplitting and poor contour quality, which affect engineering safety. To counteract the inhibitory effect of in-situ stress, water-coupled charge can be used due to its high energy transfer efficiency. In this study, an improved calculation model of crack propagation driven by the quasi-static pressure of explosion gas–water is proposed to analyze the crack propagation and coalescence under in-situ stress. Following, a three-hole numerical model is established to verify the theoretical results and investigate the inter-hole crack characteristics. The results show that the in-situ stress inhibits presplitting, while water is more conducive to presplitting than air, especially under high in-situ stress and low rock fracture toughness. The hole spacing and decoupling ratio should be reduced under high in-situ stress. Using water as the filling medium and aligning holes with the maximum principal stress significantly enhance the directional effect and are beneficial to rock damage control. Finally, optimization schemes are verified based on the excavation of deep-buried stopes. Evaluations of the 3D-scanned contour reveal that water and parallel layout increase the hole spacing by 20 % and 50 % respectively, while maintaining or even improving the contour quality.