Analysis of mining influence and feasibility study on downward mining of close-distance coal seams in Zhaoxian Coal Mine

To study the mining influence and feasibility of downward mining in the No. 2 coal seam of the Fourth Mining Area in Zhaoxian Coal Mine, the No. 3 coal seam working faces (4301—4304) and the No. 2 coal seam working faces (4201—4202) were selected as research subjects. A combined approach of theoretical analysis and numerical simulation was employed to analyze the overlying strata structure evolution and interlayer rock failure characteristics during close-distance coal seam downward mining. The results indicate that the floor failure depth induced by No. 2 coal seam mining is 9.86 m, significantly less than the average interlayer spacing of 31.09 m between the two seams. Analysis based on slip line and elastoplastic theories confirms that mining the upper No. 2 coal seam does not damage the No. 3 coal seam, allowing downward mining under proper support and safety measures. Given the small spacing between the No. 2 and No. 3 coal seams in the Fourth Mining Area, which classifies them as close-distance seams, the residual coal pillars from the No. 2 coal seam induce stress concentration in the No. 3 coal seam working face. During No. 3 coal seam mining, the roof experiences elevated stress due to the combined influence of overlying pillar stress and its own advance abutment pressure. Therefore, during subsequent mining of the No. 3 coal seam, attention must be paid to hazard control, including water inrush and residual coal spontaneous combustion.