Law of overburden migration in repeated mining of working faces in contiguous coal seams

MA Jinglong; SUN Yanbin; LI Yi; LIU Shuqiang

doi:10.11799/ce202507019

Abstract：Clarifying the overburden migration law of repeated mining of working faces in contiguous coal seams is of great significance for stope stability and surrounding rock control of mining roadways.In mining areas of Eastern China,contiguous coal seams mining is common.If a mining face is arranged in such coal seams,strong mine pressure behaviors often occur in the underlying mining roadways.In order to deeply study the overburden migration law of repeated mining in such working faces,taking the working face of Fucun Coal Mine in Zaozhuang mining area as the engineering background,a combination of theoretical derivation,numerical simulation and field measurement is used to analyze the key layer state and mining overburden migration evolution characteristics of the working face mining and overburden affected by repeated mining in the 3-upper and 3-lower coal seams.The results show that according to the calculation of key layer theory,the fracture distance of the key layer of overburden in the working face is positively correlated with its distance from the coal seam roof,and the fracture distance of the key layer is significantly reduced after secondary disturbance.The percentage of decline is positively correlated with the face width.The calculated height of the repeated mining fracture zone in the inner section of the 3-lower 1009 working face is 115.4 m.According to the UDEC numerical simulation results,the secondary movement of overburden caused by repeated mining greatly increases the range of the fracture zone,and the range of the fracture zone increases significantly with the increase of the face width of the working face.The heights of the caving zone and fracture zone in the inner section of the 3-lower 1009 working face are 32.4 m and 91.8 m respectively.The double-ended water stopper is used for field measurement of the height of the two zones of overburden.According to the water seepage of the rock strata,the heights of the caving zone and fracture zone in the inner section of the 3-lower 1009 working face are 41.45 m and 101.05 m respectively,which corroborates the theoretical derivation and numerical simulation results.