Research on staggered distance of upper and lower coal seam cooperative mining face based on subsidence prediction

In order to study the safe staggered distance of the same mining face of the upper and lower coal seams, which does not belong to the category of contugous coal seams, taking the collaborative mining face of Yitian Coal Industry No. 2 Coal Seam (overlying coal seam) and No. 11 Coal Seam (underlying coal seam) of Lu'an Group as the engineering background, based on the roof collapse characteristics of the underlying coal seam stope and the theoretical analysis results of “three vertical zones”, the scientific problem to be solved under the condition of downward cooperative mining is that the mining activities of the underlying coal seam can not affect the safety production of the overlying coal seam. A probability-integrated mining subsidence prediction model was established to explore the influence range of mining in the underlying No. 11 coal seam working face on the subsidence of the overlying No. 2 coal seam floor under full mining conditions. The subsidence of 10 mm, inclination of 3 mm/m, curvature of 0.08×10⁻³ /m and horizontal deformation of 2 mm/m were taken as the safety impact threshold of the mining of the underlying coal seam on the overlying coal seam. The criterion is that the working face of the overlying coal seam is located outside the mining subsidence range of the working face of the lower coal seam. Considering the safety factor of 1.5 times, it is concluded that the reasonable strike dislocation distance of upper and lower coal seams is 96.2 m, the ground pressure appearance of the overlying 2# coal seam working face and its mining roadway is monitored, and the ground pressure law is compared and analyzed with that of single layer mining under the same conditions. Engineering practice shows that during the coordinated mining process of No. 2 coal seam and No. 11 coal seam, based on the mining subsidence range caused by the full mining conditions of the No. 11 coal seam, the determined staggered distance of the same mining face in the upper and lower coal seams is reasonable and reliable. The overlying No. 2 coal seam working face has not been affected by the mining subsidence of the lower No.11 coal seam, which can achieve safe collaborative production.