Research on the Mechanism and Optimization of Roof Coal Anchoring Support for Weakly Cemented Soft Rock Roadway

Weakly cemented soft rock is widely distributed in Western China. Due to its low strength and poor cementation, major support problems such as roadway roof failure and subsidence instability are often encountered. As an effective solution, roof coal can effectively control the roof strata. Based on the analysis of the deformation and failure characteristics of the weakly cemented soft rock roadway roof, the supporting mechanism of retained top coal is revealed, and the reasonable roof coal thickness is simulated and given. The retained top coal supporting technology is formed and applied in the field. The main research conclusions are as follows: (1) the overall deformation and failure of the roadway roof are significant, and the local characteristics are “crack + fracture.” The roof cracks originate from the shallow part and gradually develop to the deep part; (2) as an equivalent pallet, top coal has the characteristics of high strength and strong integrity. Under the action of bolt support, it is easy to form an anchored arch structure, which significantly improves the overall stability of the roof; (3) the simulation results show that when the top coal thickness is greater than 0.5 m, the plastic zone of the roof is significantly reduced, and the reasonable top coal thickness should be greater than 0.5 m; and (4) the anchoring support concept of increasing the anchor cable spacing and adjusting the anchor cable angle is formed. On the basis of simulation, the support scheme is optimized, and the anchor cable is arranged into “3‐3‐3” type, and the angle between the anchor cable and the horizontal direction is 70°. Through the field application test, it is found that when the top coal thickness is 0.5 m, the optimized support scheme has a good roof control effect and no obvious deformation and damage.