Development range and safety evaluation of overburden fractures in upward mining of contiguous coal seams

XUE Feng; WANG Kai; YUAN Xiao; LIU Yaxin; YANG Yuhu

doi:10.11799/ce202501012

Abstract：To study the safety and feasibility of upward mining in contiguous seams,taking the 7#and 8#coal seams of Baizhuang Coal Mine as the research object,by means of theoretical analysis,FLAC3D numerical simulation,and engineering measurement,the development range of water-conducting fractures in overburden after mining in the lower 8 coal seam and the failure law of underlying rocks in different layers in the fracture zone were studied.The theoretical analysis and numerical simulation verified that the maximum height of mining caving zone and the average height of overburden fracture zone are less than the spacing of coal seam.According to the field measurement,the caving zone is within 7.3 m(vertical height)from the 8#coal;the severely fractured zone is within 7.3～14.4 m,where the water permeability is greater than 20 L/min;the fractured zone is within 14.4～21.2 m,where the water permeability is 10～20 L/min.the slightly fractured zone is within 21.2～29.6 m,where the water permeability is 5～10 L/min;and the bend zone is over 29.6 m from the 8#coal.The two coal seams are 31.6 m apart,and the 7#coal is outside the slightly fractured zone of the 8#coal,and the water leakage is less than 5 L/min,and coal seam integrity is less damaged.Therefore,it is safe and feasible to adopt upward mining in 7#and 8#coal seams.The research can provide reference for related upward mining of contiguous seams.