Study On The Butterfly Failure Mechanism Of Surrounding Rock In The Mining Roadway With Composite Roof

This paper relies on National Natural Science Foundation of China "Discontinuous deformation of rock mass in plastic zone of surrounding rock of deep roadway and its control"(51874130),combined with theoretical analysis,numerical simulation,on-site testing methods and previous research results,based on the butterfly plastic zone theory of roadway surrounding rock,taking the deformation and failure characteristics of the surrounding rock of the compound roof roadway in Xinglu coal mine as the engineering background,this paper discusses the shape of the plastic zone of the surrounding rock of the compound roof roadway,and analyzes the factors such as lateral pressure coefficient,roof type and rock dip angle The influence of the stability of the compound roof tunnel is studied.The control mechanism of the bolt(cable)to the compound roof is studied as follows:Theoretical analysis and numerical simulation show that the displacement of the roadway roof is determined by the maximum stress of the roadway location.The main reason for the separation failure of the composite roof is the change of stress state and bearing structure of the composite roof,the difference of lithology between the layers of the roof and the shear failure between the layers caused by high level stress.The greater the difference between the horizontal stress and the vertical stress,the greater the range of the plastic zone of the surrounding rock of the roadway,the greater the thickness of the hard rock layer,the lower the layer,the more stable the roof of the roadway,and the obvious development of the plastic zone of the surrounding rock along the rock layer.The structural stress of Xinglu coal mine is the main factor that affects the ground stress and the stability of the roadway in this area,and the horizontal stress is far greater than the vertical stress.It is found that the plastic zone of surrounding rock is not uniformly around the roadway,and the plastic zone in 45 ° direction on both sides of the roadway roof is larger than the plastic zone in vertical direction.Its geometric shape is similar to butterfly shape,which conforms to the butterfly failure theory.Based on the C9 return air link tunnel as the engineering background,the numerical calculation model is established,and four working conditions are simulated respectively: no support,anchor bolt support,top angle anchor cable + roof anchor cable joint support,bottom angle anchor bolt + full section anchor cable joint support.When the anchorage end is located in the elastic zone with high rock strength and good integrity,the stress concentration is weakened,the plastic zone is reduced,and the deformation of the surrounding rock of the roadway is effectively controlled.According to the deformation and failure mechanism of the deep composite roof and its control principle,and based on the principle that the support scheme should meet the coordination,gradient,deformability and integrity,according to the actual situation of the site,the comprehensive support mode of "bolt,steel mesh,shotcrete,roof and side anchor cable,bottom plate anchor cable" is proposed.The practice shows that the scheme can effectively guarantee Normal safety production of C9 return air link Lane in service period.