Failure characteristics and stress field distribution law of roadway in downward mining of deep close distance coal seam

Deep close distance coal seam mining is affected by the goaf of upper coal and remaining coal pillar, and the roadway of lower coal is difficult to maintain stability. By means of theoretical analysis, physical simulation test and numerical simulation, this paper analyzes the failure characteristics of roadway in deep close distance coal seam and the evolution law of stress field, and optimizes the reasonable layout of lower coal roadway. The results show that: (1) The analytical formula of the evolution of the floor principal stress difference with depth is derived theoretically, and the distribution law of the shear stress of the rock mass in the floor of the coal seam is obtained. (2) The airway below the goaf can maintain good stability. High stress accumulation phenomenon occurs in the transport roadway below the coal pillar, which can not keep stable. (3) Due to the stress difference under the goaf and the coal pillar, the shear stress increases and the rock mass is damaged, and the left gang of the transport roadway is prone to instability destruction. (4) By comparing the distribution characteristics of plastic zones of transport roadway at different locations, it is determined that the transport roadway is more appropriate to be arranged 45 m below the coal pillar from the goaf.