Movement patterns and pressure relief effects of overlying rock in the protection layer beneath sem1-coal seams

LIU Yanwei; YANG Eryang; HAN Hongkai; SHI Zhaoqi; ZUO Weiqin; LI Ruonan; ZHANG Fengjie

doi:10.13247/j.cnki.jcumt.20250253

Abstract：Investigating the destressing effects of different mining heights in lower protective layer of semi-coal rock under the influence of thick and hard key strata is of great significance for deter-mining a reasonable mining height,controlling gangue discharge,ensuring effective pressure relief,and achieving efficient production.Taking the 172105 lower protective layer of semi-coal rock in Jinling Coal Mine as an example,both physical similarity simulation and FLAC3D numerical model-ing were employed to reveal the fracture and movement patterns of key strata at varying mining heights,as well as their destressing effects on the protected seam.The results indicate that when the mining height is 0.8 m,the interlayer key stratum does not fracture;the overlying strata bend and subside smoothly as a whole,and the protected seam experiences insufficient destressing.When the mining height exceeds 1.15 m,the interlayer key stratum fractures,with the fracture zone developing upward to the bottom of the key sandstone stratum above seam No.2-1,resulting in significant destressing of the protected seam.It is found that when the thickness of the interlayer limestone key stratum is 8.0 m and the mining height is 1.15 m,the swelling deformation reaches 3.0‰;when the mining height increases to 1.9 m,the limestone key stratum fractures,the stress in the protected seam is reduced by 41.6％-70.2％,and the maximum swelling deformation of the protected seam increases to 23.3‰,achieving a significant pressure-relief effect.These results guide the determination of a reasonable mining height for the half-coal-half-rock protective seam at working face 172105 of Jinling Coal Mine and ensure efficient pressure relief of the protected seam.