Catastrophe mechanism and prevention and control technology on soft coal mining with large inclination angle under thick and hard roof

Aiming at the problems of rib spalling, sliding and tipping of supports and large area roof pressure of No.11513 steep dipping working face of Pansidong Coal Mine, the catastrophic mechanism and prevention technology of soft steep dipping coal seam mining under thick and hard roof were studied by means of theoretical analysis, numerical simulation and field observation. The research results show that in the initial stage of large-incline soft coal mining under the thick and hard roof, the surrounding rock damage are mainly concentrated in the coal wall and floor rock. The displacement of coal and rock mass in the adjacent working face area show that the extrusion displacement of coal wall >floor heave displacement >roof subsidence displacement.Due to the existence of thick and hard roof, as the ad vance distance of the working face increases, the displacement of the coal wall gradually increases and the instability probability of coal wall is increased gradually. According to the characteristics of rock deformation and field observations, two disaster modes of large-incline soft coal mining under thick and hard roof were proposed. One is a time-occurring disaster dominated by rib spalling and roof caving, which induces large area instability of the supporting and surrounding rock system. Another is the instantaneous disaster caused by the breakage of thick hard sandstone. Based on the catastrophic mechanism of large inclination soft coal mining under the thick and hard roof, deep hole pre-crack blasting of thick and hard roof have been adopted to control the movement of thick and hard roof. In order to ensure the stable operation of the supporting and surrounding rock system, measures are taken to reinforce the coal wall, prevent the support from falling or slipping and manage the crushing direct roof by laying metal mesh and I-steel auxiliary support. The statistical analysis of the working resistance of the support and the rib spalling showed that the rib spalling was effectively controlled after a series of prevention measures were taken at the 11513 working face.When the pressure is first applied, the working resistance of the support is relatively rich, the safety valve is less open and the supportdoes not fall significantly, which realizesthe safe and efficient mining of soft coal with large inclination under the thick and hard roof.