Controlling large deformations in soft rock roadways with integrated anchor shotcrete and grouting techniques

Effective and safe support in soft rock roadways remains a critical challenge in underground coal mining due to the extreme weakness of the rocks and their susceptibility to weathering and water invasion. This paper examines the tailgate of longwall panel 2606, a typical soft rock roadway excavated along the edges of mined-out areas with thin pillars at the Lvtang Coal Mine in Guizhou, China. Despite employing a combination of rock bolts, cable bolts, and surface support systems, significant roadway deformation was observed. The mechanisms behind this deformation were analyzed through in-situ tests and clay mineral composition analysis. These analyses revealed that the primary causes of the roadway's substantial deformation were the low strength and weathering susceptibility of the coal and surrounding rock. A novel synergistic control strategy combining anchoring, shotcreting, and grouting was proposed for supporting soft rock roadways. Detailed numerical simulations were conducted to evaluate the deformation and stability of the tailgate under various support scenarios, validating the effectiveness of the proposed support scheme. The synergistic support strategy was implemented to reinforce the 2606 tailgate, and field monitoring was conducted to assess its effectiveness. Monitoring data indicated that rib deformation with the new support design was reduced by 66% compared to the original design. The results demonstrate that the improved synergistic support system effectively mitigated large deformations and maintained the stability of the tailgate. These findings provide a valuable engineering reference for supporting and reinforcing soft rock roadways under similar geological conditions.