Rockburst Damage Characterization in a South African Gold Mine Subjected to High Horizontal Stresses

ABSTRACT: Rockburst risk can often be reduced by selecting appropriate mining or excavation methods, sequences, strategically placing developments, and other infrastructure. However, owing to the uncertainties in rock mass properties and boundary conditions, rock engineering design necessitates dependence on ground control measures reinforced with burst-resistant rock support to ensure safety at the workplace. High horizontal stress at depth aids the rockmass to be self-supporting by clamping the rockmass. It reduces the gravity-driven damages that could be experienced at the excavation, as stress-induced damages might become significant when mining goes deeper. Significant seismic events (ML≥0.9) are usually associated with large damages near any excavation in the underground workings. We analyzed the damage mechanisms of large mining-related seismic events (0.9≤ML0≤ 3.0) located within the shaft. The study indicates that with the large energy release, damages were only observed with fewer stopes. This is not only influenced by the high horizontal stresses but also by the rockmass mineralogical and contrasting geomechanical properties. The rockburst analysis within active mine infrastructure indicates that 63% large seismic events did not cause any damage to the mine infrastructure or cause injuries within the WAF. 1. INTRODUCTION Rockburst is a significant occurrence that has impacted numerous deep underground mines worldwide. Understanding this phenomenon is essential for managing such catastrophic events, which can lead to substantial increase in investment risk and loss of lives. It results from an overstressed rock mass or an intact, brittle rock and occurs when the stresses exceed the material's compressive strength. It is associated with excavation damage and is characterized by its destructiveness, suddenness, and complexity (Feng et al., 2012). However, due to uncertainties in rock mass properties and boundary conditions, rock engineering design must rely on ground control measures with burst-resistant rock support to ensure workplace safety. This ground control strategy is a norm in the deep gold South African mines. The rockburst phenomenon is driven by various factors, including mining depth, rockmass conditions, geological structures, and mining elements (e.g., abutments, pillars, etc.). In recent years, research has been increasingly addressing the global topic of reducing the challenges of rockburst. Its mitigation or prevention remains as one of the most crucial problems to be solved in underground rock engineering.