Stress distribution and crack propagation of high stress hard rock under excavation unloading-perforation fracturing

A theoretical model of stress distribution under excavation unloading-perforation fracturing was derived based on the background of perforation fracturing assisted mechanical excavation in deep hard rock mines, and a flow-coupled discrete element numerical model of excavation unloading and perforation fracturing was established. By comparing with the theoretical model, the accuracy of the numerical model was verified, then the influence of perforation position (x0), injection pressure (pt), perforation height (hf), and dual perforation fracturing on crack propagation pattern under excavation unloading condition were investigated. The results indicate that for excavation unloading-single perforation fracturing, x0, pt and hf have different influences on the stress distributions. The number of cracks increases with increasing x0, pt and hf, while the law of crack propagation is obviously different. For excavation unloading-dual perforation fracturing, the fracturing performance is better than single perforation fracturing, and the number of cracks increases with increasing hf, which will results the cracks coalescence in the middle area of perforations. © 2023 Central South University of Technology. All rights reserved.