Fragmented rock block geometry affecting mechanical responses and fluid flow characteristics during compaction of caving zones

Abstract

Underground mining plays a pivotal role in resources extraction and clean energy transition, but the safe management of caving zones remains a primary challenge. This study investigates the influence of broken rock geometries on mechanical responses of fragmented rocks and fluid flow characteristics within the mining goaf. By simulating three distinct fragment geometries, the stress-strain measurements, rock rebreakage, and size distribution variation have been characterised. The results indicate that the higher level of irregularity in the broken rock geometry, makes the material more sensitive to compaction, leading to higher degrees of breakage and more rapid reductions in structural porosity. Additionally, the pore structures extracted from the mechanical models are imported into a fluid dynamics module to measure permeability of caving zones. Findings reveal that the geometrical configuration of the pore network governs fluid transport pathways. Broken rocks with complicated geometries increase the tortuosity of pore paths, resulting in greater flow resistance and lower permeability. This study emphasises the significance of rock block morphology in controlling the compaction and fluid transportation in the goaf, providing insights into gas migration behaviour and enhancing water storage potential in goaf environments.