| When the working face of thick coal seam with extra thick sandstone roof is mined,the overlying thick hard roof suddenly collapses and loses stability,resulting in dynamic load,which disturbs the goaf and the gob side roadway behind the goaf.The mine pressure is strong,and the roadway anchorage system is easy to damage.Based on the actual production geological situation of Xiaojihan coal mine,in order to improve the maintenance status of the mining roadway,combined with the existing theoretical research results,this paper carries out the relevant theoretical,experimental and application research,analyzes the formation mechanism of the dynamic load of breaking the super thick hard roof,explores the damage law of the roadway anchorage system under the dynamic load disturbance,and puts forward the control technology of the roadway surrounding rock under the dynamic load disturbance of breaking the roof.(1)The 11215 working face of Xiaojihan coal mine is affected by the engineering geological conditions.When it is pushed to different positions,it will show the stage characteristics of mine pressure.The strength of the roadway support system will be reduced,and part of the anchorage system and surrounding rock will be seriously damaged.Because of the different displacement of the deep and shallow rock strata,the instantaneous axial tensile stress of the bolt body exceeds its ultimate tensile strength,and the bolt breaks in the shallow part;the anchor cable will produce two kinds of failure forms: tension and shear.(2)Based on the previous theoretical research results,the mechanical analysis model of the lateral hard roof structure in the process of coal mining is established,and the fracture mechanism of the rock beam structure of the lateral roof is proposed.When the cantilever beam breaks and loses stability,the accumulated elastic energy in it is released,forming "fracture dynamic load";when the upper rock beam structure breaks with the cantilever beam,it finally collapses and impacts the goaf,forming "impact dynamic load".The two dynamic load types are analyzed respectively,and the strength of two dynamic load types are obtained.(3)FLAC3D numerical simulation is used to study the dynamic response law and failure evolution process of roadway anchorage system.The results show that the dynamic load has repeated compression and tension action on the surrounding rock of the tunnel,which is easy to damage the anchorage system and even lead to the anchorage failure.Under the action of roof dynamic load,the main reason for the deformation of roadway roof is the stress difference caused by dynamic load.The deformation of roadway side is mainly determined by the dynamic response difference of surrounding rock in different depth.The axial force of roof bolt(cable)decreases first and then increases,and the axial compression force produced by the deep and shallow surrounding rock is the dominant factor;the axial force of roadway side bolt(cable)increases continuously,mainly due to the incompatible deformation of deep and shallow surrounding rock.(4)Based on the original supporting scheme,the technical measures and parameters of strengthening supporting scheme are put forward according to the characteristics of the stress and deformation of the surrounding rock of the roadway,and the mine pressure of the return air chute of 11215 working face is observed twice.The results show that the mine pressure of the return air chute of 11215 working face is normal,and the effect of the surrounding rock control scheme is good Meet the requirements of actual productionThe paper has a total of sixty-eight pictures,eight tables and seventy-eight references. |
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