Research On Instability Mechanism And Pre-Stress Control Technology Of Coal Roadway With Composite Roof

The roof of the composite roof coal road is easy to separate and sink,and the two gangs are coal bodies with low strength.Under the load of overburden,the damage of the surrounding rock of the two gangs is large,which is equivalent to greatly increasing the width of the composite roof.Supporting is extremely difficult.Therefore,in view of the problem of composite roof coal road support,combined with the geological conditions of Xiaoyan Mine,the theoretical analysis,numerical simulation and industrial test are used to systematically study the stability mechanism and control of surrounding rock in compound roof coal roadway,technology.(1)Based on the concept of critical pressure,the nonlinear M-C criterion is used to derive the calculation formula of the main strength parameters of the slip surface of coal gang and top floor.The influence of the slip surface strength parameters on the flexural deformation of the composite roof is discussed.With the increase of the internal friction angle of the slip surface,the flexural deformation of the composite roof is continuously reduced and the reduction is smaller and smaller.In-plane cohesion also has a similar influence law.(2)Based on the theory of infinite long plate,the expressions of deflection and separation of each layer of composite roof are deduced,and the factors such as composite roof coal roadway width,overburden load,elastic modulus and slip surface strength parameters are discussed.The influence law of roof stability is taken as an example.The composite roof of the 16-way 03 working face transportation roadway is taken as an example.The research shows that there is a separation layer between the coal stratification and the upper mudstone 6 on the 6th,without considering the composite roof swell deformation.Under the premise,the maximum separation value is 147mm.In addition,there is a separation layer between the composite top plate and the basic top,and the maximum separation value is 21mm.(3)The distribution of stress field,displacement field and plastic zone of surrounding rock in composite roof with no weak surface,single weak surface and multiple weak surface is studied,and the instability mechanism of composite roof coal roadway is revealed.(4)The surrounding rock control technology of high prestressed anchor support was developed,and its mechanism of action was revealed:high prestressed anchor support improved the confining pressure of surrounding rock,and the vertical stress less than 1 MPa was obviously smaller than no support.During the protection,the plastic zone of the composite roof is obviously reduced,and the failure mode of the surrounding rock in the shallow roof of the composite roof is mainly caused by the shearing failure during the unsupported transition to the shear failure of the support,and the reduction of the two branches is reduced.It is 59.9%smaller,and the amount of roof subsidence is reduced by 152.6%.The effect of high prestressed anchor support on the separation and sinking of composite roof is extremely significant.(5)Using the dynamic design method,the initial support scheme is given to determine the bolt support parameters.During the excavation,the two-way moving lane of the 16-103 working face transportation lane was 203 mm,and the displacement of the top and bottom plates was 143 mm.The high prestressed anchor support effectively controlled the surrounding rock deformation of the composite roof coal roadway.