Position Analysis And Practice Research Of Roadway Closing To Overlying Residual Coal Pillar In Hulusu Mine

The research on the position analysis and practice of the roadway under the short distance overlying residual coal pillar is of great significance for the surrounding rock control and coal mine safety production in the mining process of hulusu mine.Based on the engineering background of 22103 working face in hulusu coal mine,Inner Mongolia,this paper studies the roof caving law and rock structure of working face in upper and lower coal seam mining by using theoretical calculation analysis,physical similarity simulation experiment and UDEC numerical simulation analysis,and determines the critical width of stable coal pillar by calculating the critical value of plastic zone width of coal pillar.According to the stress distribution law obtained by UDEC numerical simulation analysis,the layout of the roadway in the lower coal seam goaf is determined and verified by UDEC numerical simulation.Finally,after understanding the law of instability and deformation of surrounding rock of roadway under goaf,the high pre tightening and long anchoring technology is selected to control the surrounding rock of roadway,and applied to the field industrial test.In the field construction process,the supporting effect is monitored from the displacement of roadway surface,stress of bolt and anchor cable,roof crack development,etc.The conclusions are as follows:(1)The movement law of roof strata under overlying coal pillar is obtained.After the mining of 21102 and 21103 working faces in upper coal seam,the rock mass of false roof and direct roof collapse is disordered.When the main roof and upper strata cross fall,they break along the vertical cracks to form relatively regular rock blocks.The rock blocks formed by the breaking are arranged orderly,and they form a hinge relationship under the promotion of horizontal stress,forming a "masonry beam" structure.Due to the superposition of support areas,the stress distribution under the residual coal pillars on both sides of the goaf presents a "bubble" shape.Therefore,when considering the layout of the mining roadway in the lower coal seam,priority should be given to the layout under the goaf.(2)It is determined that the remaining coal pillar of 2-1 coal in hulusu mine is stable coal pillar.The calculation formulas of plastic zone width of coal pillar and critical width of stable coal pillar are obtained through theoretical analysis.Combined with the engineering geological conditions of hulusu mine,the critical width of stable coal pillar in hulusu mine is 15 m ～ 18 m,and the width of coal pillar left in 2-1 coal of hulusu mine is 30 m,which is far greater than the critical width.(3)The vertical stress distribution of the floor under the overlying coal pillar is revealed.Using UDEC numerical simulation analysis combined with physical simulation experiment,it is concluded that the stress reduction area and the stress change rate reduction area are under the goaf,and the lower coal seam roadway location should give priority to the overlapping area of the stress reduction area and the stress change rate reduction area.According to the stress distribution,several different layout schemes are obtained,and the optimal layout scheme is obtained by comparing the deformation of different schemes in the numerical simulation.(4)The surrounding rock control of the roadway under the overlying coal pillar in hulusu mine is realized.According to the movement law and stress distribution state of roadway roof strata under the overlying residual coal pillar in hulusu coal mine,combined with the engineering geological conditions and field construction conditions of 22103 working face,the high pre tightening and long anchoring technology is adopted for roadway support,and the field industrial test is carried out.In the process of on-site construction,the supporting effect is monitored from the displacement of roadway surface,anchor cable stress,roof crack development,etc.,which verifies that the high pre tightening and long anchoring technology can effectively control the surrounding rock deformation of the roadway under the overlying coal pillar.There are 50 figures,9 tables and 74 references in this paper.