Damage Mechanism and Parameter Optimization of Rock Mass Blasting Under High In-Situ Stress

ABSTRACT: The response of blasting effects during deep rock excavation processes is significantly influenced by high in-situ stress conditions. It plays a pivotal role in guiding both the preliminary design and subsequent implementation of support systems. This paper utilizes numerical simulation methods to simulate blasting under high in-situ stress, wherein the detonation process of high-energy explosives was simplified as instantaneous loading applied to the borehole walls. Through a combination of numerical simulations and on-site experiments, the study explores the evolution of blasting-induced damage. Adjustments and optimizations are applied to the blasting sequence, blasthole layout and explosive charge weight. The findings indicate that the scope of rock damage is reduced with the increasing of in-situ stress, there exists a transition of rock failure mode from tensile-shear to compressive-shear, and the detrimental effect of blast on tunnel safety matters less and less. In addition, excessively large spacing hinders effective penetration, while too small spacing will reduce the blasting efficiency. Under the circumstance with a constant borehole layout, the explosive charge governs the evolution of the blasting damage zone and the pre-blast area exhibits cyclic cumulative damage. 1. INTRODUCTION Blasting in rock masses holds significant importance for engineering construction. In the past time, researchers have concentrated on the entire process of rock damage (initiation, propagation, and temporal evolution), as well as the mechanism of crack propagation with respect to the distance from the blast hole experimentally and simulation-based. The effectiveness of rock breaking primarily manifests through the action of detonation gases generated by explosive initiation and the propagation of stress waves that cause damage to the rock mass. Under the influence of blasting gases, rock damage near the blasthole is predominantly in the form of tensile failure (Pramanik Hagan, 1980; Trivino & Mohanty, 2015).