Control Technology Of Retracement Roadway Surrounding Rock In Lower Coal Seam In Huangbaici Mine

The roadway with regenerated roof in close distance lower coal seam is affected by the superimposed mining stress of upper and lower coal seams.The roof is particularly broken and the bearing capacity of surrounding rock is low.In this thesis,the Guo Neng Wu Hai energy Huang Bai Ci mine 021005 withdrawal channel safety application as the research background,using the method of field test,theoretical analysis,numerical calculation,industrial test and so on,to close the lower coal seam working face goaf,coal pillar and solid coal under three mining conditions of mine pressure behavior law,roadway roof mining stress evolution law,fracture distribution law,plastic failure characteristics,grouting key technical parameters and support parameters are studied,put forward the regeneration roof grouting reinforcement + partition support surrounding rock control technology,finally carried on the field application,the following results are obtained.(1)The distribution characteristics of working resistance of hydraulic support under different mining conditions in the working face of close lower coal seam are analyzed,and it is found that the support pressure is generally high under the goaf and the residual coal pillar,and the strata behavior is strong,and the strata behavior under the solid coal is weak.It is determined that the pressure range of stoping mining at the end of mining period is 7.57～10.16 m from stoping mining line,which can effectively optimize the stress environment after withdrawal channel excavation.(2)The failure depth of goaf floor in upper coal seam is calculated to be 18.5～18.8m.Based on the mining stress,fracture evolution law and plastic failure characteristics of roadway roof in close lower coal seam under different mining conditions,the control time of surrounding rock of goaf,coal pillar and solid coal roadway roof is determined to be 13～200m,8～13m and 8～25m from stop mining line,and the height of grouting reinforcement is 6m,7m,8m respectively.(3)The main factors affecting the stability of roadway surrounding rock in close distance lower coal seam are revealed,and the control principle of roadway surrounding rock under goaf in close distance coal seam is put forward : Increasing the length of anchor rod,Improving the anchorage force of anchor rod and anchor cable,and Grouting to improve the mechanical parameters of surrounding rock.The control principle of roadway surrounding rock under coal pillar is : grouting reinforcement to strengthen the mechanical properties of surrounding rock;increasing support density and timely reinforcement support.(4)Based on the numerical calculation results,it is determined that the reasonable grouting pressure of the roof of the withdrawal channel under the goaf is 1.5 ～ 2 MPa,the reasonable grouting time is not less than 30 min,the grouting hole spacing is 6 m,and the row spacing is 4 m.Reasonable grouting pressure is 3～ 3.5MPa,reasonable grouting time is not less than 16 min,grouting hole spacing is 4.5m,row spacing is 4m;reasonable grouting pressure is 2 ～ 2.5MPa,reasonable grouting time is not less than 10 min,grouting spacing is 3m,row spacing is 2m.(5)Through numerical simulation and field mine pressure observation,it is found that in the allowable deformation range,the stability of the surrounding rock of the channel is good under different mining conditions,which verifies the feasibility of grouting reinforcement and zoning control technology and achieves good practical results.This thesis includes 79 graphs,10 tables and 73 references.