Study On Reasonable Width And Stability Of Coal Pillars Adjacent To Goaf

Reasonable setting of coal pillar width is an important condition to ensure the stability of roadway and the safety and efficient production of coal mine.It has important social and economic value for saving coal resources and protecting the life safety of production personnel.Based on the engineering background of a coal mine in Tongchuan mining area,this paper analyzes the reasonable retention and stability of coal pillars along the goaf adjacent to the mine by using the methods of theoretical analysis,numerical calculation and on-site monitoring.The main contents are as follows:(1)Based on the masonry beam theory,considering the support of the caving gangue in the goaf to the roof,the mechanical models of different fracture positions of the basic roof are established,the stress of the roof at different fracture positions of the basic roof is analyzed,and the calculation formula of the stress of the coal pillar under the static condition is deduced.It is obtained that the basic roof is the most unfavorable fracture position when it is fractured above the roadway.(2)According to the force of different fracture positions of the basic roof on the coal pillar,considering the load of the mining face on the coal pillar,the average stress of the coal pillar at different fracture positions of the basic roof is deduced.Combined with the ultimate strength criterion of the coal pillar,the width of the coal pillar at different fracture positions of the basic roof is calculated.Combined with the engineering geological conditions,by comparing the reserved widths of coal pillars at different fracture positions,it is obtained that the reserved width of coal pillars is 20 m when the most unfavorable fracture position of the main roof is maintained.(3)The influence of overburden load qB,basic roof lateral caving distance lB,fracture position distance x0 from solid coal side and burial depth H on the width of coal pillar is analyzed.The results show that the width of coal pillar increases with the increase of overburden load qB and basic roof lateral caving distance lB,and decreases with the increase of fracture position distance x0 from solid coal side.(4)By using the discrete element software UDEC,the stress field and plastic zone width of 20 m coal pillar under the most unfavorable fracture position of the basic roof are analyzed.By comparing with the field monitoring and theoretical calculation results,the accuracy of reasonable setting and stability analysis of coal pillar along the adjacent goaf is verified.