Mine Pressure Behavior of Gob-Side Entry Retaining by Roof Cutting in Closely Spaced Coal Seams

To study the influence of the mined-out area in the nearby upper section of a coal seam on the mining of the working face of the lower seam, in this study, the mining of the 18–4 working face using the 110 mining method in the Dongrong No. 2 Mine, Jixian County, Heilongjiang Province, China, was taken as the engineering background. The 3DEC discrete element numerical simulation method was used to simulate the mining conditions close to the upper coal seam. The seam spacing was set as 5, 10, 15, and 35 m, and the influence of the pressure on the working face of the lower coal seam was investigated based on comprehensive analysis of field measured data. According to the results, as the distance between the coal seams decreased, the stress and displacement of the roof of the surrounding rock increased and the stability distance of the roadway decreased. During roadway reuse process, as the coal seam spacing decreased, and displacement of the surrounding rock increased and the leading influence range of the roadway decreased. Under the influence of slit, the roof pressure on the side near the slit is lower than that on the side near the coal wall.