Study on the failure mechanism and control technology of surrounding rock of soft rock roadway near fault

Based on the serious deformation and failure of the surrounding rock of a soft rock roadway near a fault in a coal mine,a combination of experimental testing,theoretical analysis and numerical simulation was used to analyze the original mining roadway support plan and its effect,and the coal mine roadway surrounding rock broken zone near fault was studied.The range of rock fragmentation zone,the law of tectonic stress,and the disintegration and softening characteristics of mudstone weathering and water were studied.The control measures for the deformation of the soft rock roadway near the fault were studied,and "the anchor belt mesh spray + hollow grouting anchor cable" combined supporting technology solutions were proposed.According to the actual conditions of the return airway in No.2408 working face,this paper observes the surrounding rock of the newly excavated roadway through drilling videos.It is concluded that the surrounding rock of the roadway is relatively broken between 1～3 m,and less broken between 4～5 m,but there are also some small fissures.The surrounding rock control of the soft rock roadway near the fault zone of the mine should fully consider the reinforcement of the surrounding rock in the broken zone; The results of in-situ stress measurement show that the tectonic stress of the fault in the mine is mainly horizontal stress,that is,the influence of horizontal stress should be fully considered in the control of surrounding rock of mine roadway.Numerical simulation analysis shows that when the original support scheme is adopted for the roadway,the maximum deformation of the left side,right side,roof and floor of the roadway is -109,-160,-133,-112 mm respectively; when the optimized support scheme is adopted for the roadway,the maximum roadway deformations of the left,right,roof and floor of the roadway are -66,-65,-49，-86 mm respectively,that is,the deformation of the surrounding rock is significantly reduced,and the technical parameters of optimized combined support of the mining roadway are determined.Field test results show that the surrounding rock of the roadway gradually stabilized after 40 days of excavation of No.2408 return air roadway,and the relative moving amount and roof subsidence amount of both sides were less than 50 mm.Compared with the deformation of the surrounding rock in the section with the old support,the surrounding rock deformation of the roadway is reduced by more than 50%,and the surrounding rock deformation of the roadway was effectively controlled.