Overburden fracture and overlying coal seam migration laws in shallow and thick seam mining
Aiming at solving the problem of hard determination in overlying rock breaking rules and stability of overlying thin coal seams in mining face of shallow and thick coal seam,a large-scale similarity simulation model is constructed based on No.8 panel face at Sandaogou Coal Mine.The theoretical analysis,similar simulation,and on-site measurement methods are combined to study the fracture and migration laws of overlying rock and the stability of overlying thin coal seams after recovery.The research results showed that:After calculation,it is determined that the main roof of No.8 panel area is between No.5-2 coal seam and the overlying thin seam.The fracture and migration control the formation and migration of longitudinal fractures of overlying coal seam.The occurrence of the overlying thin coal seam above the main roof hinge zone is unstable,with some separation layers and large fractures.Above the coal pillar and goaf,the occurrence is relatively stable and continuous.As the lower thick coal seam face continues to advance,the overlying caving zone and fracture zone of No.5-2 coal seam will gradually expand upwards in a trapezoidal shape,and gradually affect the overlying thin coal seam,increasing fragmentation on thin coal seam and reducing the integrity.After the completion of No.5-2 coal seam recovery,the overlying No.4-4 and 4-3 coal seam will all occur as round-shape sinking.The expected maximum subsidence of No.4-4 coal seam reaches 4.5 m and that of No.4-3 coal seam reaches 4.3 m.
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