Study On Stability And Control Of Roadway Surrounding Rock Under Extremely Close Goaf In Zhengli Mine

In view of the fact that the roadway under the extremely close goaf is located in the stress reduction area,but it is affected by the upper mining,the roof rock layer is loose and broken,the stability of the surrounding rock is poor,and the support is difficult in the process of roadway excavation.Based on the actual production conditions of 14102 working face in Zhengli Coal Industry,this thesis comprehensively uses the research methods of field measurement,theoretical calculation,numerical simulation and engineering application to study the failure characteristics and stress distribution law of roadway surrounding rock,the effect and influencing factors of broken roof bolt,and the support mode and parameters of roadway under extremely close goaf.The main results are as follows:（1）The physical and mechanical parameters of 4^#coal seam and its roof in Zhengli Coal Industry were measured.The average compressive strength of 4^#coal was 18.65 MPa,the tensile strength was 0.94 MPa,the internal friction angle was20.3°,and the cohesion was 1.03 MPa.The average compressive strength of roof sandy mudstone is 23.44 MPa,the tensile strength is 1.74 MPa,the internal friction angle is 23.6°,and the cohesion is 1.94 MPa.The average compressive strength of 4^#coal seam floor is 44.62 MPa,the tensile strength is 2.59 MPa,the internal friction angle is 37.6°,and the cohesion is 3.87 MPa.The roof strength is low and is damaged by 4^-1#mining,which is the difficulty of surrounding rock control of 4^#coal seam mining roadway.（2）After the numerical simulation of 4^-1#coal seam mining,the maximum plastic failure depth of the floor can reach 16 m,and the theoretical calculation shows that the maximum damage depth of the mining floor after the upper 4^-1#coal seam mining is about 11.4 m,which is greater than the maximum interlayer spacing between the two coal seams of 4^-1#and 4^#coal seams.Through drilling peeping,it is found that the damage degree of roadway roof under different interlayer spacing of 4^#coal seam is quite different,and the damage degree of roof rock layer decreases with the increase of interlayer spacing.（3）The anchorage test of broken rock mass is carried out by PFC^3D.When the separation layer between the two coal seams is more than 2.4m,the broken rock mass of the mining roadway can form a stable pressure arch structure and can bear the weight of the broken rock mass in the goaf.In order to ensure the formation of a stable pressure arch in the anchorage zone of the broken roof and support the overburden pressure,it needs strong side support,sufficient bolt preload,appropriate thickness and size of the broken rock mass,and stable broken rock mass under the arch.（4）According to the interlayer spacing of roadway roof and the failure characteristics of surrounding rock,the partition support scheme of roadway under extremely close goaf is designed.When the interlayer spacing is less than 1.5m,the singleπbeam shed support is adopted,and the short bolt is used for reinforcement.When 1.5m～2.6m,bolt combined with singleπbeam shed support is adopted;2.6m～5.2m when using bolt support,roof pressure signal shed to strengthen monitoring;when is greater than 5.2m,bolt support is used and anchor cable is reinforced.（5）The numerical simulation is used to optimize the partition support parameters of the roadway under the goaf of the extremely close distance coal seam,and the partition support scheme of the track crossheading of the 14102 working face of Zhengli Coal Industry is determined,and the field application is carried out.The support scheme effectively controls the deformation of the roadway and meets the requirements of the safe production of the 14102 working face.There are 68 figures,17 tables and 73 references in this paper.