## 6 Conclusions  
(1) The occurrence mechanism of the large deformation of the surrounding rock in a withdrawal roadway during mining activities has been revealed, which includes three aspects of the influence of front abutment pressure on the coal mining face, including the stress superposition exceeding the bearing capacity of the surrounding rock, the damage accumulation of the surrounding rock in the withdrawal roadway during a long mining cycle, and the fluctuation evolution of mining-induced stress. Among them, the fluctuation evolution of mining-induced stress has often been overlooked in the past, but it may be the most important cause of the large deformation and instability of the roadway surrounding rock. (2) A method has been proposed to determine the excavation timing of the withdrawal roadway. The adoption of the proposed method not only allows for a reasonable project arrangement during the construction period, but also avoids the impact of advanced mining of the working face on the withdrawal roadway during excavation. From the perspective of facilitating the maintenance and control of the withdrawal roadway, the sum of the influence ranges of the abutment pressure between the working face and the roadway can be selected as the safe distance to avoid significant disturbances. (3) The anti-disturbance principle of thick-layer anchorage has been clarified. The single layer of the roadway roof is characterized by its thinness, lack of stability, and susceptibility to deformation. When multiple thin rock layers are transformed into thick and well-integrated anchored layers through anchor support, the stability and disturbance resistance of the roof can be greatly improved. The thickness of the anchored rock beam is a sensitive factor that affects the maximum subsidence and maximum tensile stress of the roof and is crucial for ensuring the safety of the roadway roof. (4) A novel double-layer flexible support technique has been proposed. In this support scheme, 1860-MPa-grade flexible steel strands are used as the carrier, overcoming the limitation of the rigid anchor bolt length limited by the roadway height, and achieving thick anchorage. The thick fundamental anchorage layer is constructed with the first layer of flexible support, and the thicker reinforced anchorage layer is constructed with the  
Figure 11: The effect of field application in withdrawal roadway 21405: (**a**) The deformation; (**b**) A photograph of withdrawal roadway 21405 after mining. second layer of flexible support. Through this double-layer flexible and thick anchorage, the mining disturbance to the withdraw roadway can be effectively resisted. Specific explanations have been provided for the thickness, per-tightening force, and key support positions of the support. The calculation method of the thickness \(h\) of the roof support has also been also proposed. (5) Based on the application site of the withdrawal roadway in working face 21405 of the Hulusu coal mine in Inner Mongolia, China, the technical effect verification has been provided. The withdrawal roadway has a buried depth of 650 m, a coal thickness of 3.4 m, a rectangular cross-section shape, a width of 4.8 m, and a height of 3.4 m. The application of new double-layer flexible support technology has achieved ideal results in controlling roadway deformation after the completion of mining. Conceptualization, C.H. ; methodology, C.H. and G.D.; software, Y.Y. ; validation, G.D. and G.H. ; investigation, W.L. and H.Y. ; data curation, G.D. and G.H. ; writing--original draft preparation, C.H. ; writing--review and editing, Y.Y. and G.D.; project administration, G.H. All authors have read and agreed to the published version of the manuscript. This research was funded by the National Natural Science Foundation of China (No. 52274101; 52034007) and the China Postdoctoral Science Foundation (No. 2019M652019). Not applicable. Data Availability Statement: Data is contained within the article.