The Active Roof Supporting Technique of a Double-Layer Flexible and Thick Anchorage for Deep Withdrawal Roadway under Strong Mining Disturbance

Due to the strong disturbance of a mining face, the surrounding rock of the withdrawal roadway is susceptible to deformation and failure, which restricts the safe and efficient evacuation of mining equipment. To resolve this longstanding technical problem in mine production, an engineering investigation, numerical simulation, theoretical analysis, and other research methodologies were conducted in this study. Furthermore, the influence mechanism of mining-induced stress on the withdrawal roadway was revealed, the anti-disturbance principles of thick-layer anchorage of roadway roofs were elucidated, and a novel double-layer flexible support technique was proposed. The front abutment pressure, stress superposition, damage accumulation of the surrounding rock, and the fluctuation of mining-induced stress are the primary factors contributing to the significant deformation of the surrounding rock in a withdrawal roadway. However, the fluctuation of mining-induced stress has usually been ignored in previous studies, and it may be the most crucial cause of the significant deformation and instability of the surrounding rock. The thickness of the anchored rock beam is the most vital factor affecting the maximum subsidence and maximum tensile stress of the roof, and increasing the thickness of the anchored rock beam can significantly improve the stability and anti-disturbance performance of the roof. In the proposed double-layer flexible supporting technique, flexible steel strands serve as the carrier, which overcomes the constraint of the roadway height on the length of roof support components. The first layer of flexible support is used to construct a thick fundamental anchorage layer, while the second layer is employed to construct a thicker reinforced anchorage layer, facilitating the effective resistance of the roof against strong mining disturbances. The effectiveness of this technique was further validated through the application of an engineering practice. The research results have reference value for solving the difficult problem of mining roadway support.