Study On Deformation Mechanism And Bolt Mesh Shotcrete Combined Support Technology Of "Three-Soft" Coal Seam Roadway In Tianshuibao Coal Mine

Taking the large deformation of the trapezoidal section air return roadway in the1304 working face of the "three soft" coal seam in Tianshuibao Coal Mine as the engineering background,this thesis comprehensively studies the deformation mechanism of the roadway by using indoor tests,theoretical analysis,numerical calculation,industrial tests and other methods,and puts forward the surrounding rock control technology of "arc arch roadway section+bolt mesh shotcrete",and verifies the reliability and effectiveness of the technology through industrial tests.The main research results are as follows:(1)Through the indoor mechanical parameter test,the physical and mechanical characteristics of the roof and floor of the return air roadway and the coal body in the1304 working face are mastered;The detection results of the roadway roof crack development show that the shallow part of the roadway roof is broken to a large extent,in which the breakage,crack development and separation occurred within 0～2.16 m;The results of in-situ stress test show that the maximum horizontal stress of the roadway is about 1.91 times of the vertical stress,and the overall roadway belongs to the medium in-situ stress area.(2)The stress distribution characteristics of the surrounding rock of the air return roadway in 1304 working face are calculated,and the characteristics of asymmetric development of high and low slope plastic zones caused by different stress concentration levels at the shoulder corners of the roadway are clarified.Through numerical calculation,the stress evolution and deformation process of surrounding rock of roadway are clarified.Combined with the field measurement results,the mechanism of large deformation of surrounding rock caused by the combined actions of low strength of surrounding rock,water physics and weathering,roadway roof fragmentation,and uneven stress distribution of surrounding rock is comprehensively revealed.(3)Combined with the surrounding rock deformation mechanism of the air return roadway in 1304 working face and the actual geological conditions of the roadway,a large deformation control scheme of "arc arch section+bolt mesh shotcrete" is proposed,and numerical calculation and analysis of different roadway section shapes and support parameters are carried out using FLAC3 D simulation software.The numerical calculation results show that "the row spacing between bolts is 800×800 mm+row spacing between anchor cables 1400 × 1600 mm+350 N·m bolt pre tightening torque,230 k N anchor cable pre tightening force " roadway support parameters and arc arch roadway section can better control the deformation of surrounding rock.(4)The optimal arc arch section shape and support scheme calculated by numerical method are applied to the air return roadway of 1304 working face,and the construction technology of roadway bolt mesh shotcrete support is formulated.The rock pressure monitoring results of the roadway show that the maximum deformation of the roadway surrounding rock is 62 mm,the maximum stress of the roof anchor cable is 220 k N,and the maximum displacement of the roof from the deep base point and the shallow base point of the stratum are 9 mm and 7 mm respectively.The industrial test shows that the surrounding rock control technology of "arc arch roadway section+bolt mesh shotcrete" can effectively solve the problem of large deformation of the roadway.The thesis includes 66 figures,12 tables and 90 references.