Structural model of hard overburden shell in thick coal seam and its application

Taking the mining of extra-thick coal seam of Carboniferous hard overburden in tongxin coal mine of datong mining area as the engineering background, the movement characteristics of hard overburden in fully-mechanized caving mining of 3-5 # extra-thick coal seam are analyzed based on the key stratum theory. Based on the elastic plate theory, the mechanical model and mathematical model of the cylindrical shell structure of hard overburden in large space stope are established, and the ultimate span of the cylindrical shell structure is determined and applied in 8105 working face.The results show that the limit span of sub-key stratum II in 8105 working face is 65.11 m, and the limit span of main key stratum is 222.77 m. The calculation results are basically consistent with the actual mine pressure behavior. The mechanism of special mine pressure phenomena such as large and small periodic weighting, large mining influence range and easy impact load in the mining process of 8105 working face is revealed, which provides a theoretical basis for mine pressure control in the mining face of Carboniferous hard overburden and extra-thick coal seam in Datong mining area.