A case study on the deformation and failure mechanism of a soft rock mining roadway in the Xin'Shang'Hai No. 1 coal mine, China

Abstract

Mining roadways in soft rock are seriously deformed and damaged, which affects the normal production of the mine. Based on the Xin'Shang'Hai No. 1 Coal Mine project, a true 3D physical model test was carried out to obtain the deformation evolution and failure features of the mining roadway. The results show that the strata movement of the panel drives the surrounding rock of the mining roadway to deform toward the center; the net size of the roadway near the longwall face decreases by 48.3%. The convergence of soft rock mining roadways can be divided into four phases, and the average convergence rate of a fast phase is 3.1 times that of a slow phase. The evolution of roadway failure is deformation accumulation → sidewall cracking → lining spalling → coal sidewall breaking → floor heave → bolt (cable) failure → full section deformation. Coal sidewall failure is an important turning point of mining stress-induced roadway failure. The extension of the broken area into the rock leads to the failure of the coal seam between the roof and floor and then induces the overall instability of the roadway. The radial deformation and stress evolution of the mining roadway are analyzed by numerical simulation, and the model test results are verified. The mining roadway in soft rock shows full section convergence characteristics under the stress of mining. Finally, countermeasures are proposed according to the failure mechanism to provide a reference for similar roadways.