## 3 Impact of Mining on Withdrawal Roadway
### Influence Mechanism of Mining-Induced Stress on the Withdrawal Roadway  
This study has demonstrated that there are four primary factors contributing to the severe deformation of the surrounding rock in the withdrawal roadway during mining activities, as follows:  
(1) Abutment pressure. After roadway excavation, the abutment pressure is formed on both sides of the coal bodies. After coal seam mining, the roof of the coal seam undergoes periodic fracture, leading to stress transfer from the gob to the periphery. Among them, there is a high value of front abutment pressure distributed in front of the working face. As shown in Figure 4, the peak value of the abutment pressure on both sides of the roadway is 22.8 MPa, which is 1.22 times higher than that of the original rock stress. The front abutment pressure significantly increases, and its peak value reaches 55.18 MPa, which is 3.25 times higher than that of the original rock stress. The abutment pressure caused by coal mining is 2.4 times higher than that caused by excavation. Therefore, the withdrawal  
Figure 3: Numerical calculation model of the withdrawal roadway and the working face: (**a**) The spatial relationship and size of the model; (**b**) Numerical modeling and in situ stress field. roadway is more prone to deformation when it is disturbed by the mining of the working face. This is consistent with previous studies [16]. (2) Stress superposition. When the coal mining face is still at a certain distance from the withdrawal roadway, the front abutment pressure has already been superimposed with the abutment pressure inside of the surrounding rock of the withdrawal roadway. Figure 5 shows the vertical stress evolution of the coal seam roof when the working face is gradually advanced to the withdrawal roadway. When the distance between the working face and the withdrawal roadway is 245 m, the stress variation in the withdrawal roadway is the smallest. When the distance is 180 m, the stress variation is relatively small. When the distance is 115 m, the abutment pressure on both sides of the withdrawal roadway increases slightly. When the distance is 55 m, the abutment pressures on both sides are superimposed onto each other, and these values show a significant increase. When the distance between the two is 5 m, the position of the peak abutment pressure has already crossed the withdrawal roadway and reached the rear of the withdrawal roadway, and the peak stress is as high as 68.45 MPa. When the superimposed stress exceeds the bearing capacity of the surrounding rock (especially the coal body), a strong deformation of the withdrawal roadway occurs. Figure 4: Distribution curve of abutment pressure: (**a**) The abutment pressure of coal mass on both sides of the withdrawal roadway; (**b**) Front abutment pressure of working face 21405. Figure 5: Vertical stress distribution curve at different distances between the working face and the withdrawal roadway. (3) Damage accumulation. During the disturbance period, the surrounding rock of the withdrawal roadway exhibits stress-induced responses. The deformation and failure of the rock mass are the most evident manifestations. Due to the continuous occurrence of stress variations, rock mass damage continues to accumulate, ultimately resulting in large deformation and instability. (4) Stress fluctuation. Although stress fluctuation has often been overlooked in previous research, it plays a crucial role in the deformation and instability of the roadway surrounding rock under strong mining disturbance. Figure 6 shows the stress distribution nephogram of the rock layer when the working face is advanced to a distance of 115 m, 55 m, and 5 m from the withdrawal roadway, respectivley. Figure 5 shows the stress value of the coal seam roof. At this time, the stress of each point in the figure seems to be determined, while the stress at every point in the rock mass undergoes a complex wave-like evolution process.