A Failure Mechanism of Supports in Weakly Cemented Soft Rock Roadways and the Synergistic Support Design

Weakly cemented soft rock roadways are prone to severe roof lowering and floor heave, especially under strong mining. The failure of bolt (cable) supports is significant. Theoretical analysis, on-site monitoring, and numerical simulation were used in the work to solve this problem. Firstly, the work explored and obtained the failure characteristics of bolts (cables) in the weakly cemented gob-side entry. The entry was mainly composed of tension fractures and tension-shear fractures in the free section, supplemented by the shear failure of floor and roof. The failure process of bolts (cables) was explored. The insufficient pre-tightening force of bolts (cables) was the internal cause of the failure mechanism of supports based on the on-site monitoring results. The large deformation of roof sinking beyond the extended range of support materials was the external cause of the failure mechanism of support. We proposed the concept of rapid support with high pre-tightening bolt-cable synergistic deformation. The support required the deformation of bolts (cables) to be coordinated with roof deformation. A design for rapid support with bolts and cables was formed. The pre-tightening force of the weakly cemented gob-side entry was optimized based on the numerical simulation. Finally, the on-site application of our method could reduce roadway deformations and the failure of bolts (cables).