Coal pillar width optimization and control technology in isolated working face with large mining height under thick-hard strata

ZHANG Tong; ZHANG Ningbo; LI Ting; LIU Qiyuan; CHEN Baobao; WU Dongyuan

doi:10.11799/ce202503015

Abstract：The determination of reasonable coal pillar size in isolated working face with large mining height is one of the key factors affecting coal recovery rate and safe mining.Taking the No.15115 isolated working face with large mining height in Huangyanhui Mine as the research object,a coal pillar superposition-loaded mechanical model was constructed for the coupling effect of thick hard rock deflection-coal mass collaborative compression and hard rock cantilever additional stress,and the reasonable width was determined.The main conclusions are as follows:The loading at the roadsides is mainly determined by the effect of thick-hard rock stratum deflection and compression deformation of coal by its own weight,while the loading at the goaf side comes from the additional stress of the lateral cantilevering rock stratum.The load and ultimate bearing capacity of the coal pillar show a reverse trend in the width,and the minimum width is 9.4 m.The sensitive point of the equivalent fracture angle on reducing the load strength of the coal pillar is determined to be 82°.In the simulation,the proportion of plastic failure range and the degree of coal mass expansion in the increasing of the coal pillar width decreases.The stress concentration in the middle of coal pillar tends to stabilize,and the overall bearing performance is enhanced.Finally,the column width was determined to be 10 m.Engineering practice proved that,after fracturing on both sides of the roadway,the rock fracture penetration weakened the integrity of the thick and hard rock strata,2.0 m elastic zone was retained in the middle of the coal pillar,and the convergence of the roadsides and the roof-floor was controlled within 520 mm,achieving safety protection of the island face roadway.