## 3 Numerical Simulation Analysis and Demonstration of Actual Extraction Sequence in Large Stopes
### Simulation Result Analysis of the One-Step High-Profile Working Face Extraction Process  
This simulation takes the 60-10# working face as an example to analyze the stepwise extraction process. Due to the uniform structure of the working faces in the Dongguanshan  
Figure 8: Simulation results after extraction of the 60-7# working face. (**a**) Maximum principal stress contour map; (**b**) minimum principal stress contour map; (**c**) roof displacement contour map; and (**d**) displacement contour map on both sides. mining area, the results of the 60-10# working face simulation can also be applied to optimize the extraction sequence of other one-step working faces. The numerical simulation results are analyzed through sectional views along the direction of the working face, with a total of 10 extraction cycles carried out sequentially. The extraction results are shown in Figures 9 and 10. Figure 9 shows the compressive stress cloud diagram and the plastic deformation cloud diagram before mining. From the figure, it can be observed that there are large compressive stress areas at both ends of the 60-10# mining area, with a maximum compressive stress of 35.5 MPa, indicating that the mining area is in a shear state. Through Figures 9 and 10, it  
Figure 10: Numerical simulation results after the completion of all mining operations. (**a**) Maximum principal stress contour map; (**b**) minimum principal stress contour map; (**c**) displacement cloud diagram; and (**d**) plastic zone distribution. Figure 9: Simulation results before the extraction of the 60-10# working face. (**a**) Minimum principal stress cloud map; and (**b**) plastic zone cloud map. can be seen that the empty area is not subjected to tensile stress; however, after the first end of the mining area is excavated, the maximum compressive stress at the excavation site is released, while the compressive stress at the other end of the mining area continues to increase. The maximum displacement is mainly located at the top of the empty area, and the maximum displacement value is also continuously increasing. The distribution of the plastic zone in the empty area changes from shear-past at the initial excavation to shear-past and shear-now after excavation, indicating that the empty area has previously reached the yield surface but later returned to an elastic state, with some elements also in a shear state. During the continuous excavation process, the main changes are in the maximum compressive stress and maximum displacement values. We calculated the maximum compressive stress and maximum displacement trend during the stepwise mining process. It can be seen that, during the initial mining process, the maximum compressive stress gradually increases, peaking after the eighth step of mining, reaching a maximum of 39.1 MPa. By the ninth step of mining in the 60-10# panel, the total thickness of the mined area reaches 72 m. In the final two steps of mining, the maximum compressive stress decreases rapidly, indicating some release of stress. From the displacement curve, it is observed that the displacement is relatively large in the early stages of mining, but the trend of increasing displacement slows down during the stepwise mining process, eventually stabilizing, without any sudden changes in displacement. Overall, using this mining method may lead to a continuous increase in the maximum compressive stress on the other side of the mining area, potentially causing crushing damage to the surrounding rock in the mining chamber. The 60-6# and 60-10# panels at Dongguashan have already suffered significant damage, and adopting this approach may exacerbate the destruction of the surrounding rock in the mining chamber. From Figures 11 and 12, it can be seen that the maximum principal stress cloud map indicates that, as mining progresses gradually, the surrounding area of the mined-out section is not subjected to tensile stress.