Abstract:
Aiming at the problems of large deformation and difficult support of gob-side entry driving with narrow coal pillar in closed-distance coal seams group of Tucheng Coal Mine, to determine a reasonable surrounding rock control scheme for the roadway, this paper adopts the combination of theoretical analysis, numerical simulation and field practice to study the maximum failure depth of the floor after the stoping of the overlying coal seam working face, the reasonable width of the reserved narrow coal pillar, the stress influence of superposed stress induced by upper and lower coal seam mining on the roadway driving position, as well as the stress distribution and deformation-failure characteristics of roadway surrounding rock after excavation. On this basis, a surrounding rock control scheme for the roadway is put forward, and its rationality is verified by field measured data. The results show that the maximum failure depth of the floor is 17.1 m after the stoping of the overlying coal seam, which is smaller than the vertical distance between the two coal seams; the reasonable width range of the narrow coal pillar is 2.48-3.57 m, and the final narrow coal pillar width of 3.0 m is determined by engineering analogy method. Numerical simulation results demonstrate that the mining of single upper or lower coal seam has little impact on the stress of roadway driving area, while the simultaneous mining of upper and lower coal seams produces a remarkable stress effect on the driving area. The surrounding rock of the roadway shows asymmetric deformation: the deformation of roof and rib on the coal pillar side is larger than that on the solid coal side, and the floor heave on the solid coal side is greater than that on the coal pillar side. After adopting the active-passive combined support scheme, the roof-floor deformation of the roadway is reduced to 82% of that with the original support, and the rib deformation is reduced to 67%, presenting an ideal surrounding rock control effect and verifying the rationality of the proposed support scheme. This research reveals the stress influence of upper and lower coal seam mining on gob-side entry driving with narrow coal pillar in the intermediate coal seam, which can provide reference for similar gob-side entry driving engineering with narrow coal pillar under the same mining and geological conditions.