Numerical Investigation on the Ground Response of a Gob-Side Entry in an Extra-Thick Coal Seam

This study was aimed at the large deformation phenomenon of rock mass surrounding the gob-side entry driven in a 20 m extra-thick coal seam. Taking tailgate 8211 as the engineering background, a numerical investigation was employed to analyze the deformation law of the gob-side entry. The study results are as follows. (1) Because the immediate roof was composed of weak coal mass with a thickness of 17 m, the roof coal mass was vulnerable to fail with the effect of overlying strata pressure; thus, a visual subsidence of roof coal mass with a maximum convergence of 800 mm was observed in the field. (2) The bearing capacity of the coal pillar was significantly less than that of the panel rib, resulting in the pillar failing more easily under the ground pressure and then generating large-scale squeezing deformation. (3) The roof and panel rib were in a state of shear failure with a failure depth of about 5 m. The coal pillar was entirely in a state of plastic failure. (4) A support scheme including an asymmetric anchor beam truss, roof angle anchor cable, and anchor cable combination structure was proposed. The field work confirmed that this support scheme could efficiently control the deformation and failure of the rock mass surrounding the gob-side entry. This study provides the theoretical basis and technical support for the control of rocks surrounding the gob-side entry in similar conditions.