Study on the fracture characteristics of pre-grooved rock under particle impact

Abstract

Particle-impact rock breaking is a feasible technology for fracturing deep, high-strength rock under high confining pressure. However, its effective fragmentation extent in hard rock is limited and the breaking efficiency remains low, which restricts engineering application. To address this issue, an auxiliary pre-grooving approach is proposed to enlarge the fragmentation extent and improve rock-breaking efficiency. Particle-impact tests were conducted on pre-cut-grooved rock specimens. The particle velocity was determined using a high-speed imaging system, and the post-impact failure morphology was quantified in combination with 3D scanning. Based on these measurements, a quantitative evaluation model for particle-impact rock breaking under grooved conditions was established, and the effects of groove parameters on impact-induced fracture behavior were systematically investigated. The results show that grooves, acting as prefabricated defect planes, markedly guide crack propagation during particle impact. Groove depth primarily controls the fracture depth, whereas groove spacing governs whether cracks can effectively extend to the grooves and coalesce into through-going fractures. When high-velocity particles vertically impact the center of double-grooved specimens, the failure mode evolves with increasing groove spacing from wedge-splitting to conjugate, unilateral, and crushing, among which the conjugate mode is the most representative. To efficiently evaluate rock-breaking performance and identify the optimal grooving scheme, a conjugate-product model was developed using the endpoint depth, midpoint depth, and fracture length of the deepest fracture section. Under the present test conditions, the optimal parameters are a groove spacing of 35 mm and a groove depth of 40 mm, corresponding to a fragmented volume of 32,043.62 mm³.