Study on roof and coal pillar stability of residual coal re-mining face in Jincheng Mining Area

According to the roof flling problems existed in the secondary mining face in the residual seam of No.3 seam in Jincheng Mining Area, a coal pillar stre ss gauge was firstly applied to measure the vertical stress of the residual coal pillar, then a rectangle thick plate model of the residual seam roof in No.3 seam was est ablished, a theoretical analysis was conducted on the flexure deformation of the residual seam roof and the subsidence law of the residual seam roof was obtained. The study results showed that the arch or oval roof falling was occurred at the residual coal pillar and the gateway cross point, a stress concentration phenomenon was occ urred in the residual coal pillar of the residual coal pillar area, the coal pillar was pressed in to the floor and a layer or arch roof falling was occurred. The vertical stress in the central location of the residual coal pillar was the max and was about 13.7 MPa. The goaf of the residual coal pillars would be a stress reduced area. The vertical stress between the two coal pillars was mini. The subsidence value of the residual seam roof was increased along the four sides based on the residual coal pillar as the center. The subsidence was distributed in oval, the subsidence value of the two side roof of the residual coal pillar was the min, but the subsidence value of the coal pill ar goaf and gateway cross point, the intersection and other location roof was high.The study results could provide the theoretical support to prevent the roof falling difficf ulty of the residual coal.