Study On Mine-induced Stress Of Reused Roadway In Longwall Mining With Two Gateroad Layout In Yangquan Mining Area

The reused roadway in longwall mining with tow gateroad layout serves two working faces.Because it is affected by the excavation of adjacent roadway and mining of two working faces,the evolution law of mining-induced stress and the deformation and failure characteristics of surrounding rock are different from the general roadway.This paper is based on the background that double-roadway arrangement with reserved entry gas tail roadway in 81115 working face of Pingshu coal mine in Yangquan mining area.Field investigation,geological mechanics test,field measurement and numerical simulation are used to carry out research and experiment.On the basis that the investigation on the deformation and damage characteristics of the similar excavation activities in roadways,the geological mechanics parameter test is carried out on the test roadway,including surrounding rock structure observation,surrounding rock strength test and geostress measurement;By installing a test stand in a test roadway,we monitor the excavation of roadway and evolution law of the reserved entry surrounding rock's mining-induced stress?deformation characteristics during the mining of 81115 working face.Using FLAC~3DD software to analyze the deformation and failure characteristics of surrounding rock and the evolution law of mining-induced stress during the roadway service time.The main research achievements are as follows:(1)The original rock stress field in the reserved entry is?_V(29)?_H(29)?_h,it belongs to the middle stress value region.,It is the optimal layout direction that the direction of roadway arrangement is approximately perpendicular to the maximum horizontal principal stress direction under the condition of the original rock stress field.(2)The impact range of the reserved entry is about 45m and the tunneling disturbance is generally small,it is mainly affected by the advance and rear support pressure of the work face.Deformation of the reserved entry occurs mainly in the rear area of the working face,and it is asymmetric.Because the surrounding rock beside drift pillar is affected by mining,the peak value of vertical stress and plastic zone is greater than that of solid coal side.(3)By means of the hollow inclusion strain gauge to monitor the roof mining stress,then the main stress size and direction evolution law of the roof of coal pillar,roadway and solid coal are obtained.(4)During the mining of 81117 working face,due to the total plastic failure of 20m pillar in the recovery process of the 81115 working face,the bearing capacity has been greatly reduced and the roadway is severely deformed.(5)With the increase of coal pillar size,the deformation and damage characteristics of roadway surrounding rock are improved,at the same time,the peak value of mining-induced stress in coal pillar and solid coal decreases.Stress in coal pillar changes from the unimodal"steep and warped"distribution to the bimodal"slow and flat"distribution.The improvement of surface displacement and surrounding rock damage of the reserved entry is most obvious while coal pillar size change from 20m to 25m,even to 30m.Continue to increase the size of the pillar,the improvement effect was reduced.Combining comprehensive consideration of economic cost,the coal pillar size can be 25m.(6)This paper proposes the improvement suggestions of Pingshu coal mine.