Research On Deformation Failure Mechanism And Support Optimization Of Deep Composite Roof Dynamic Pressure Tailentry Of No.5 Coal Seam In Renjiazhuang Coal Mine

The 210504 return air chute of Renjiazhuang coal mine is arranged in coal seam 5.The average thickness of the coal seam is 4.95M,the inclination angle is 16°～20°,and the buried depth is about 600m.There are many layers of roadway roof,the shallow fissures of rock stratum are developed,and the integrity is poor.It is a composite roof.Affected by the mining of adjacent working faces,the roadway has been excavated for two months,the maximum subsidence of roof is 500mm,the maximum approach of two sides is 1200mm,and the maximum floor heave is 1500mm.The large deformation and failure of roadway surrounding rock seriously threaten the safety production of the mine.Therefore,the deformation and failure mechanism and support optimization of deep composite roof roadway in No.5 coal seam of Renjiazhuang coal mine are studied.Using the comprehensive research methods of field investigation,numerical simulation,theoretical analysis and field test,this paper has carried out a series of research and Practice on the deformation and failure mechanism and support optimization of deep composite roof dynamic pressure roadway in No.5 coal seam of Renjiazhuang coal mine.Theoretical analysis shows that there is a negative correlation between the stiffness and the number of layers of Renjiazhuang 5 coal composite roof,a positive correlation between the maximum deflection and the number of layers,and the roof is easy to separate and destroy.The numerical simulation shows that the range of about 8m above the coal pillar of 20m along the 210504 return air chute enters the plastic state,and the edge of the goaf is 10m close to the side of the coal pillar X The range of 5m all enters the plastic state,the middle lower side of the coal pillar is significantly larger than the upper side,the roof bolt and anchor cable have a significant impact on the dislocation of the shallow composite roof rock stratum,the rod body at the root of the bolt is obviously deformed,and the lower part of the anchor cable is bent as a whole.According to the field measurement,the anchor bolt and anchor cable are at the low prestress level,Comprehensive analysis shows that the deformation and failure mechanism of surrounding rock of 210504 return air roadway is large deformation and failure of surrounding rock of composite roof roadway under the joint influence of deep dynamic pressure and unreasonable support.Through the analysis of roadway bolt preload,numerical simulation,theoretical calculation and the engineering analogy of 210504 transportation chute and 110902 transportation chute,the 210504 return air chute support scheme and parameters are optimized,the high preload strong support scheme of "bolt+anchor cable+W steel belt+anchor mesh" is proposed,and the industrial test is carried out.The practice shows that the subsidence of roadway roof,the inward movement of coal pillar wall,the inward movement of mining face wall and floor heave are reduced by 76.2%,55.4%,76.3%and 61.3%respectively compared with the original support,and good results are achieved.