Numerical investigation on the assessment and mitigation of coal bump in an island longwall panel

This study presents a numerical investigation to assess the risk of coal bumps and produces a stress–relief technology using boreholes to mitigate risk during the extraction of an island longwall panel. Based on the geological condition in an island longwall panel in the Tangshan Coal Mine, Tangshan, China, a numerical FLAC3D (Fast Lagrangian Analysis of Continua in 3 Dimensions) model was established to determine and to map the zones in the panel with a high risk for coal bumps. The results of the numerical modeling show that the roof deformation starts to occur at more than 30 m ahead of the longwall face and the deformation starts to accelerate after a distance of 10 m in front of the longwall face. Large and rapid roof deformation is considered to be an important precursor of coal bump occurrence during the extraction of an island longwall panel. Based on the numerical results, a stress–relief technology using boreholes, which was employed to release abutment pressure, was investigated through numerical methods. The modeled results suggest that the peak stress concentration could be released by drilling boreholes in the zones prone to coal bumps. The effectiveness of the stress release increased with the borehole length and decreased with the borehole spacing.