| The occurrence conditions of coal seams in China are complex,and the composite roof occupies a large proportion.Under the harsh conditions of deep earth with ' three high and one disturbance ',the maintenance of deep composite roof roadway is very difficult,and the roadway has the phenomenon of ' pre-excavation and post-repair,failure or even scrapping ' all the year round.The key factor of roadway surrounding rock control is the interaction between supporting resistance and surrounding rock deformation.In this thesis,from the perspective of the interaction between surrounding rock deformation and bolt,especially considering the influence of composite roof interlayer on roadway stability,the deformation and failure characteristics of composite roof roadway and the optimization of bolt support technology are systematically studied by means of laboratory test,numerical simulation,engineering practice and field monitoring.The following regularity is obtained:(1)The physical and mechanical parameters of ore-rock are obtained by laboratory tests.The deformation and failure characteristics of surrounding rock of composite roof roadway are systematically studied by numerical analysis.The variation laws of stress,deformation and plastic zone distribution of surrounding rock with the number of weak interlayers,bedding dip angle,buried depth and horizontal stress are obtained.The physical and mechanical parameters of ore and rock are obtained by laboratory tests.The deformation and failure characteristics of surrounding rock of composite roof roadway are systematically studied by numerical analysis.The variation laws of stress,deformation and plastic zone distribution of surrounding rock with the number of weak interlayers,bedding dip angle,buried depth and horizontal stress are obtained.The research shows that with the increase of the number of weak interlayers,the plastic state of roof surrounding rock is more complex,and the roof separation is intensified.With the increase of rock dip angle,the distribution of stress,displacement and plastic zone of roadway will rotate along the normal direction of bedding plane.The delamination is mainly caused by vertical stress,but high-level stress will aggravate the development of delamination.(2)The bond stiffness of the bolt with different cement mortar mix ratios was measured by bolt pull-out test,and the influence of bond stiffness on the resistance increase speed of the bolt was analyzed.Taking the mechanical model of composite roof anchorage unit as the research object,the variation of surrounding rock deformation and axial force of bolt with the thickness of weak interlayer,bedding dip angle,horizontal stress,pre-tightening force and bond stiffness were systematically studied by means of numerical simulation.The quantitative relationship between the above five influencing factors and surrounding rock deformation and axial force of anchor rod was established.The synergistic relationship between surrounding rock deformation and axial force of bolt was discussed when the parameters of each factor were changed.(3)By means of numerical simulation,the variation laws of surrounding rock deformation of roadway with composite roof and axial force of bolt with weak interlayer position,horizontal stress,pre-tightening force,bond stiffness and other factors systematically studied.The influence of different factors on the stability of composite roof roadway with weak interlayer under bolt support is analyzed,and it is found that the axial force of bolt presents the evolutionary characteristics of jump growth with the development of roof separation.When the weak interlayer is located at the edge of the anchorage zone,it is the most unfavorable factor affecting the stable production of the roadway.The axial force of the bolt fluctuates disorderly with the overall subsidence of the anchorage layer,and the working anchorage force is lower than the initial pre-tightening force when the stability is stable.This law can be used as a precursor to the roof fall of the roadway.(4)Based on the field measured data and FLAC3 D numerical simulation analysis,the relationship between abutment stress distribution,surrounding rock deformation and bolt axial force under mining influence is studied.The surrounding rock stability control measures of composite roof roadway with weak interlayer are put forward,and the optimization design method of composite roof roadway based on bolt axial force nondestructive testing technology is established.The method is applied to the surrounding rock stability control practice of deep-buried roadway with composite roof with weak interlayer in a mine in Huainan.The rationality and scientificity of the research conclusions are verified by field dynamic monitoring.The research results have important engineering guidance value for predicting and preventing roof fall accidents of compound roof roadway.This thesis has 87 figures,26 tables and 111 references. |
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