Research on movement and displacement failure features of top coal and strata in fully mechanized top coal caving mining in thinner thick seam

The top coal and strata movement, failure and stress distribution law was obtained from the systematic analysis on the top coal and strata mechanics features of the fully mechanized top coal caving mining in the thinner thick seam with the FLAC3D numerical simulation. The research results showed that the displacement value of the top coal in the fully mechanized top coal caving face was obviously higher than the displacements in the middle and bottom coal. The moving point of the top coal was at the front of the face wall. The initial moving position of the top coal and strata at the caving mining face was at the pilot bottom and the vertical displacement value would be steadily increased with the distance to the face reduced. At the front of the fully mechanized top coal caving mining face, the top coal and strata above the face would be always in the compressed status in the vertical direction. While at the top of the face, the top coal would start to have a separated phenomenon. The loads on the hydraulic powered supports the coal mining face were mainly the deformation pressures occurred from the top coal and basic roof deformation movement. Therefore the design of the hydraulic powered supports for the fully mechanized coal mining face in medium thick seam are not suitable for the fully mechanized top coal caving mining face.