Interaction between support and surrounding rock in 8.8 m super mining height working face

It is difficult to control the surrounding rock of 8.8 m super high mining face because of its high mining height and high mining intensity.The column pressure sensor and displacement sensor are used to monitor the support working resistance and roof subsidence in the whole mining process,and this paper analyzes the law of mine pressure behavior,working resistance cycle curve of support,roof subsidence and coal cutting cycle subsidence curve,and studies the relationship between working resistance,initial support force,support stiffness and roof subsidence.The research results show that the working face with super large mining height has the macro characteristics of obvious regional pressure,rapid increase of resistance,constant resistance of non pressure,and large and small periodic pressure.The roof subsidence of working face has obvious space-time difference,showing the characteristics of low at both ends-high in the middle\" in space,showing the characteristics of large roof subsidence during weighting period and small roof subsidence during non weighting period in time.The support working resistance ΔF-T and roof subsidence ΔS-T homogenization cycle curves of working face are highly consistent,they both show logarithmic large slope linear compound growth during weighting period,and nearly constant or small slope linear growth during non weighting period.There is a linear relationship between roof subsidence and support working resistance,which increases with the increase of support working resistance.When the safety valve is opened for a long time,the roof subsidence speed gradually transits from rapid increase to slow increase.At present,the ZY26000/40/88 hydraulic support can control the roof subsidence within a certain range during a certain period of pressure,but it can not prevent it from sinking further.The roof control effect shown by the support force and the rigidity of the support is particularly obvious.With the increasing of the initial support force,the roof subsidence and subsidence speed decrease significantly and tend to be stable,and the critical point is 15 MN.The relationship between roof subsidence and support stiffness is hyperbolic.When the support stiffness reaches 14 MPa/m,the inhibition of support stiffness on roof subsidence is weakened,and the roof subsidence tends to be stable.