Study of presplit blasting under high in-situ stress

Abstract

High in-situ stress generally results in difficulties in achieving crack interconnection in presplit blasting, which can further arouse challenges related to construction cost and schedule of rock engineering. In this study, the crack interpenetration in presplitting under high in-situ stresses is theoretically analysed according to the propagation and superposition of stress waves, and then the relationships between in-situ stress, hole spacing and charge diameter in presplitting are analytically established. Following, based on the theoretical results, the rock cracking and crack coalescence induced by presplitting under different in-situ stresses are numerically investigated with a two-hole planar model in LS-DYNA. The simulation results demonstrated the effectiveness of presplitting. Subsequently, to provide guidance for practical application, presplitting with multi-holes in circular tunnel excavation under high hydrostatic pressure and high anisotropic in-situ stress is numerically performed. The performances of presplitting under high in-situ stress using different methods such as changing hole spacing and adjusting charge diameter are analysed and compared. Based on the theoretical analysis and numerical findings, we suggest that drilling boreholes along the direction of the major principal stress, using less charge, and employing small and uniform hole spacing can be effective in presplitting under high in-situ stress. This study provides insights into the mechanisms of crack interpretation in presplitting and offers guidance for overcoming difficulties in controlled blasting under high in-situ stress.