Study On Surrounding Rock Stability Mechanism Of The Supporting Top Coal Roadway Controlled By Long And Short Roof Anchor Cables

At present,the main roadway in thick coal seam mining is in the form of top coal roadway along the bottom.The top coal of the top coal roadway has poor integrity and high degree of fragmentation.The anchorage force attenuation caused by this phenomenon makes the supporting problem of the top coal roadway has always been a difficult problem in mine support.The purpose of this paper is to explore the failure characteristics of the surrounding rock of the top coal roadway and the reasonable supporting scheme suitable for the top coal roadway.The following conclusions are drawn:1)Based on field test and numerical calculation,the failure characteristics of surrounding rock of the top coal roadway are analyzed.It is concluded that the development of cracks in roof of roadway will further reduce the bearing capacity of the gang,so the failure of the whole surrounding rock presents the characteristics of "synergistic expansion".At the same time,the overdevelopment of cracks in roof surrounding rock will cause roof.The rapid attenuation of prestressing force in plate support structure in the process of diffusion leads to poor roof control effect of supporting coal roadway,which further affects the stability of the whole surrounding rock.2)The mechanics model of roof structure and elastic-plastic mechanics model of coal gang in the top coal roadway are established.The interaction mechanism between roof and two sides of supporting roof coal roadway is elaborated by analyzing the deformation characteristics of roof coal and rock girder and surrounding rock of supporting roof.At the same time,the criterion of roof instability and failure is put forward,and on the basis of which the improvement of the strength of pre-stressed bearing structure can effectively restrain roadway deformation and failure.3)Based on material mechanics,elasticity mechanics and Hoke-Brown strength criterion,the stress distribution characteristics and mechanical state of surrounding rock under short anchor rope support are analyzed,and the mechanism of short anchor rope support for roof stability control of the top coal roadway is revealed.4)Based on the effective prestress diffusivity,the prestress matching of long and short anchor cable combined support of roof was studied by numerical simulation.The results show that the strength of the composite bearing body of the shallow roof surrounding rock anchorage has a linear relationship with the prestress of the short anchor cable.When the supporting parameters of the short anchor cable are fixed,the effective prestress diffusivity in the whole anchorage range increases with the increase of the prestress of the long anchor cable.On this basis,the matching range of the prestress of the long and short anchor cable in the test roadway is determined.5)An orthogonal test scheme with three factors and four levels is established to study the influence of the row spacing between long and short anchor cables,the length of short anchor cables and the length of long anchor cables on the control effect of roadway roof surrounding rock.The simulation results are analyzed by SPSS numerical analysis software.The results show that the row spacing between long and short anchor cables is the key influencing factor for roadway surrounding rock support,and the best top coal is obtained.The matching scheme of long and short anchor cables in roadway.6)The application effect of the research scheme is validated by taking the return air passage of 80807 working face of Yangmei No.2 Coal Mine as the test roadway.The monitoring results of the stress and deformation of bolt cables during the application of the scheme indicate that the coupling degree of long and short bolt cables is relatively high,the force of bolt body is stable,and the deformation of roadway surrounding rock is small,which verifies the reliability of the support scheme.