Failure Mechanism and Rib-Roof Synergistic Support Technology for Bottom-Driven Roadways in Deep Thick Coal Seams

Roadways driven along the floor of thick coal seams, while retaining the top coal, form “thick coal seam floor roadways.” These large-section roadways feature a composite coal-rock roof and weak coal ribs, leading to low overall strength and poor stability of the surrounding rock. Significant deformation and “necking” often occur, accompanied by roof falls and rib spalling, which are exacerbated under high stress or adverse geology, threatening mine safety and production. In this study, the 2201 haulage gateway in Yingpanhao Coal Mine is investigated to address surrounding rock control in such deep roadways. Using field investigation, theoretical analysis, numerical simulation, and similar simulation tests, the failure mechanisms of ribs and roofs are analyzed. Rib failure is characterized by tensile fracture in the shallow zone, splitting failure in the medium-depth zone, and incomplete conjugate shear in the deep zone. Corresponding mechanical models are established, and a method for calculating total rib failure depth—combining tensile/splitting and shear failure depths—is proposed, along with a bolt length design formula. Based on this, a synergistic roof-and-rib support technology is developed. The failure mechanism and optimal support scheme are validated through simulation tests and successfully applied in the field, demonstrating satisfactory performance. The findings provide a valuable reference for support design in similar mining roadways.