Assessment and mitigation of coal bump risk during extraction of an island longwall panel

Abstract This study presents an integrated approach for field tests and numerical investigations to assess the risk of coal bumps. This approach produces a stress-relief technology using boreholes to mitigate risk during the extraction of an island longwall panel. The field tests were conducted in an island longwall panel in the Tangshan coal mine in the city of Tangshan, China. In these tests, roadway roof displacement and electromagnetic radiation (EMR) of roadways in the panel were investigated to determine the zones of intensive roof deformation. A numerical model FLAC 3D (Fast Lagrangian Analysis of Continua in 3 Dimensions) was established to understand the results of the field tests and to map the zones in the panel with a high risk for coal bumps. The results of the field tests and 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 these results, a stress-relief technology using boreholes was investigated through numerical methods. The modeled results suggest that the abutment stress 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.