Breaking laws and stability analysis of damage main roof in close distance hypogynous seams

In order to understand the broken and instability laws of damage main roof in close distance hypogynous coal seams,the damage types of main roof in hypogynous coal seams were classified and the quantitative method of main roof’s damage was also put forward,then the breaking length of the damage main roof and the laws of the damage main roof’s instability based on the “S-R” theory of the “voussoir beam” were analyzed theoretically. The research shows that:① The damage causes the main roof’s break in advance and the breaking length decreases with damage increa- ses,the main roof breaks immediately following the coal seam excavation when the damage reaches a limit;② Sliding instability of the damage main roof occurs more easily,the more damage,the more sliding instability,and the decrease of hinged rock blocks’ extrusion force is the reason for the above phenomenon;③ The declining rate of hinged rock blocks’ extrusion force is faster than that of hinged surface’s compressive strength,and the damage main roof’s rotary instability occurs difficultly on the contrary;④ The laws of the damage main roof was proved according to the mineral pressure observation at No. 8707 working face of No. 11 coal seam in No. 307 panel of Jinhuagong Coal Mine.