Study on stability of dangling structure in ascending mining contiguous coal seams

In order to solve the problem of floor subsidence risk when the ascending mining face is pushed into the goaf ope-off cut hole of the lower coal seam,a ty pical ascending mining face A6-103 in the west well of Guici Mine in Xinjiang Uygur Autonomous Region was selected,and the overburden fracture mechanism was obta ined by studying the structure form of the lower roof and floor of the ascending mining with Repeated mining by theoretical analysis and similarity simulation method,an d the ascending mining with three-hinged arch structure was proposed.The results show that a special block structure is gradually formed in the up-mining working face of the close coal seam group through the upper cutting hole of the goaf in the lower coal seam,and the predetermined fracture position generated by the mining of the C oal seam below the structure is the intermediate hinge point.The structure can only maintain stability by relying on the support of the dangling structure formed by the k ey stratum in the inter-layer strata,and the stability criterion and calculation equation of the model are obtained.Through similar simulation results,it is proved that the st ructure cannot maintain stability in the process of stoping under the above conditions,and the suspended structure at the goaf cut boundary of the lower coal seam will suffer secondary instability,resulting in the sudden collapse of the roof and floor of the upstream mining face .At the same time,the corresponding prevention and control measures are put forward to ensure the safety of mining.