Study On Roadway Stability Control Of Different Locations Below Goaf And Coal Pillars

During the process of mining in the contiguous seams,the stress distribution of the bottom rock was changed by the stress concentration of coal pillars after the completion of the upper coal recovery and the collapse of the roof,and the integrity of the lower coal seam roof was affected directly.In the process of coal mining of lower coal,the large stress of the surrounding rock and the poor roof stability led to serious deformation of the roadway and it was difficult to support well.Therefore,this thesis is aimed at the stress distribution and the failure characteristics of the lower coal in the contiguous seams and the stability control of roadway.The research has theoretical and practical significance.In this thesis,the mining of coal seam 8 and coal seam 9 of Jialequan Coal Mine is taken as the research background.Based on the theoretical analysis,numerical simulation study,engineering applications and other methods,this thesis studied the law of the rock pressure distribution in the contiguous seams,the failure characteristics of the roadways in different places and stability control of roadway surrounding rock in the lower coal.The main conclusions are as follows:(1)Analyzed the disturbance law of upper coal seam mining to the lower rock by the theory of slip line field and got the calculation method of the lower strata maximum damage depth influenced by upper coal seam mining.Based on the actual geological conditions of Jialequan coal mine,the stress distribution law of rock strata with different depth under goaf were calculated and analyzed.The results showed that the largest disturbance happened to vertical stress in the lower coal seam.The vertical stress of the lower strata is more than the original rock stress within the range of 5m on both sides of the coal pillar.The vertical stress of the lower strata is less than that of the original rock stress out of the range of 5m on both sides of the coal pillar.(2)With the narrowing of the spacing between the strata under pillars and the upper coal pillars,the vertical stress of the strata increases obviously,reaching a maximum of 16 MPa,which is 2.56 times of the original rock stress.After the roadway excavation,the horizontal stress and shear stress change of the surrounding rock are small,but the vertical stress is obviously increased,increasing by 1.4 ~ 1.7 times,and the stress concentration of the surrounding rock is obvious.The maximum vertical stress of the surrounding rock of the roadway under the goaf is 9MPa,and the maximum vertical stress of the roadway under the pillar is 25 MPa.(3)The roadway beneath the mined-out area was affected by the pressure relief effect of the overhanging goaf,and the rock pressure on the two sides was reduced,the shear failure area was small and the overall stability of the roadway was good.But when the lower coal roadway under the coal pillar excavated,the shear failure range of roadway surrounding rock was obviously increased and the deformation of roadway was serious because of the influence of coal pillar stress concentration,especially the shear fissure of the two sides of the roadway surrounding rock developed and the roof sink was obvious.(4)Based on the analysis of the distribution law of the surrounding rock and the stability of the roadway,optimized the roadway supporting parameters of the roadway under the coal pillar of Jialequan coal mine.Engineering application and monitoring results showed that the deformation of roof and floor of the roadway were obviously reduced and the force of the cable was reasonable and the shear failure area of the roadway was reduced.This indicated that the optimization program on the roadway support was good to ensure the safety and stability of the roadway.