Research on control methods of automatically-formed roadway without coal pillar for extremely close-distance coal seams

WANG Qi; LIU Jiting; JIANG Bei; XUE Haojie; GAO Hongke; JIANG Zhenhua

Abstract：The traditional longwall mining of extremely close-distance coal seams is affected by remaining coal pillars and collapse of the goaf.During the mining process of lower working face,the stress environment is com-plex and the mining pressure is severe,inducing large deformation of roadway.To solve the problems above,we proposed a control method for directional roof cutting and constrained high-strength support of automatically-formed roadway(AFR)without coal pillars under extremely close-distance conditions.By directional pre-splitting of the roof,the long cantilever structure of roof is actively changed and the stress transfer from the goaf to the roadway roof is cut off.The crushing and swelling characteristics of rock mass are fully utilized,the high-strength support is combined to strengthen the integrity of roadway roof,and jointly realize the AFR without coal pillars.A model of overlying rock structure for extremely close-distance coal seam mining is established,and the support resistance of the automatically-formed roadway on the roof of the lower coal seam is calculated.Taking typical extremely-close coal seams as the engineering background,the numerical experiments were conducted to compare different mining methods.The results show that the stress of the roadway surrounding rock decreased by 59.8％,and the deformation of the roadway roof decreased by 70.8％.The control mechanism of the automatically-formed roadway without coal pillars in extremely close-distance coal seam mining was clarified.On this basis,we have conducted research on the design andsite application of typical extremely-close-distance coal seam engineer-ing.The results show that the method effectively reduced the occurrence of mine pressure and ensured the safe and stable control of the automatically-formed roadway.