Elastic strain energy redistribution and ground control through large diameter borehole pressure relief in a coal roadway under intense mining disturbance

Abstract To inform the selection of borehole pressure relief parameters for coal roadways under intense mining disturbance, this study investigates the pressure relief zone, elastic strain energy redistribution, and ground control performance in the 50502 haulage roadway at Nangou Coal Mine using elastoplastic analysis, FLAC3D simulations, and field monitoring. The results show that the extent of pressure relief is governed primarily by plastic zone evolution. It increases with borehole diameter, vertical stress, and the lateral stress coefficient, but decreases with cohesion and the internal friction angle. Borehole drilling reduces energy storage in the shallow coal and shifts the energy concentration deeper into the coal mass. Under the conditions investigated, the peak energy density at depth increases rapidly when the borehole diameter exceeds 240 mm, whereas the energy density at the original peak location decreases markedly when the borehole depth exceeds 12 m. Boreholes with a diameter of 180 mm, a depth of 20 m, and a spacing of 1 m, combined with graded support and truss support, reduce the maximum roof-to-floor and rib-to-rib convergence by 23.5% and 56.1%, respectively. These findings indicate that pressure relief and support design must jointly account for shallow pressure relief, energy concentration at depth, and the load-bearing requirements of the surrounding rock.