Study on deformation zoning of overlying strata and simulation of rock pressure behavior in longwall top coal caving mining

ZHAI Xinxian; GUO Zhaoyang; FANG Jianchang; ZHANG Zhiyong; ZHAO Xiaofan

doi:10.12438/cst.2024-0991

Abstract：At present,longwall top coal caving(LTCC)mining is main mining method for safety and efficiency mines with extremely-thick coal seam in China.However,the deformation movement law of overlying strata on LTCC face directly affects rock pressure behavi-or of LTCC face,selection of hydraulic supports,and selection of top coal caving technique and parameters,etc.Based on the engineering background on LTCC face 13200 in Gengcun Coal Mine,using similar simulation test and theoretical analysis,the paper studied the whole process of deformation,movement and caving of overlying strata,their deformation zoning,and the characteristics of rock pressure beha-vior of LTCC face.The results show that:①It is determined that there are multi-layer key strata on LTCC face,i.e.,the lower,middle,up-per and main key strata.According to the collapse instability characteristics of key strata in different layers,the whole process of deforma-tion movement of overlying strata on LTCC face is divided into four deformation stages.Each deformation stage is related to the collapse instability of key stratum in different layers.②After the collapse instability of the lower key strata in LTCC mining,with the continuous increase of LTCC face advancement,the middle,upper and main key strata in the fractured zone have separated from their lower strata be-fore the collapse instability.Before the collapse of the key strata,the collapse arch is formed in its lower strata,and the height and width of the collapse arch are positively correlated with LTCC face advancing distance.③The collapse instability of each key stratum on LTCC face directly causes the peak stress concentration factor Kmax of the front abutment pressure to increase.When the lower key stratum col-lapses and loses stability,the phenomenon of large periodic weighting occurs on LTCC face,the weighting interval is larger,but the weighting strength is lower;the collapse of the middle and upper key strata or the main key stratum will cause the lower key stratum to collapse at the same time,and the phenomenon of small periodic weighting occurs on LTCC face.The weighting interval is smaller,but the weighting strength is higher.The research conclusions provide theoretical basis and technical supporting for LTCC face with the gently-inclined and extremely-thick coal seam in Gengcun Coal Mine.