Asymmetric deformation law and differentiated control technique for the roadway of an isolated working face in an extra-thick coal seam

The rib corners and roof of the 23,109 material roadway of the island working face in Xiegou Coal Mine suffer severe deformation and lacks effective support during its entire life cycle. In response to this problem, the surrounding rock deformation characteristics and stress transfer law during both the excavation and mining phases of the roadway were elucidated through an integrated research approach incorporating on-site measurement, theoretical calculation, and simulation analysis. The following research findings were yielded: After the mining of the adjacent 23,111 and 23,107 working faces, the edge of the 23,109 working face becomes a fractured zone where the stress is highly concentrated in a circular shape, while the central area remains within the original rock stress zone with a relatively low degree of stress concentration. When the roadway is excavated in such an environment where the stress is high at both ends and low in the middle, the surrounding rock experiences tensile failure in the shallow part and shear failure in the deep part. Besides, the initially approximately symmetrical deformation of the roof, floor, and ribs transforms into asymmetric deformation characterized by faster subsidence of the ribs and roof. During the mining of the 23,109 working face, the advanced abutment stress is adjusted. At a distance of 7 m ahead of the 23,109 working face, the maximum principal stress concentration zone shifts towards the side of the 23,109 working face. Meanwhile, the original plastic zone in the roof, particularly near the rib corners, expands rapidly and connects with the newly formed plastic zone in the overburden. Based on the asymmetric plastic failure characteristics of the roadway, a zonal differentiated synergistic control support scheme was proposed and applied on site. Field test results demonstrate that the roadway deformation satisfies the safe production requirements of the mine.