Overburden Migration Law of Lower Stope in Cilinshan Mine Coal Seam Group

Double-action of upper and lower faces will aggravate the overburden migration, primary and secondary fractures develop into water flowing fractures during lower coal seam mining coal seam group, the water in roof and gob will greatly restrict the safe and efficient mining of the lower working face. In order to solve the mining problem of such face, the similar material experiment and theoretical analysis method are adopted to study overburden migration and the laws of overburden migration of coal seam in the lower working face of Cilinshan Mine is studied. Results show that the first and average periodic weighting distance of Cilinshan Mine lower mining face is 55 m and 18.7 m, the collapse angle of the rock mass is greater than the cut hole in the side of the coal wall, lower face mining will disturb the coal pillar in the upper face, broken fracture will penetrate the gob in upper face and be not closed easily on the side of the upper wall face, and then evolve into water flowing fracture, the lower face will suffer from rock impact and water threat in goaf, overburden migration has reducing-increasing-reducing evolution characteristics, upper face overburden settlement is larger than the lower face.