## 5 Analysis and Discussion of Numerical Simulation Results
### Study on Mechanical Behavior Characteristics of the Surrounding Rock at Stratigraphic Boundary
#### 5.1.2 Study on the Distribution Characteristics and Evolution Law of Displacement Field  
The distribution and evolution patterns of the displacement field during roadway excavation are crucial for researching surrounding rock stability. To study the deformation  
Figure 13: Stress Concentration Degree of the monitoring characteristic points at different distances.  
characteristics of the roadway when passing through different formations, a total of five monitoring points, A (arch top), B (arch shoulder), C (side wall), D (arch foot), and E (arch bottom), were selected on the profile surface of the roadway. The monitoring sections were selected as y = \(-\)19 m, y = \(-\)17 m, y = 19 m, with an interval of 2 m for one section, to capture the deformation behavior of the surrounding rock in the whole excavation region. The displacement values at different monitoring points in different monitoring sections are plotted in Figure 14. With the continuous advancement of the excavation process, in the C\({}_{1}\)d formation, the displacement at the arch bottom is the largest, reaching 69.3 mm, while the displacement at the arch foot is the smallest; in the D\({}_{3}\)zg formation, the displacement of the arch top is relatively larger, reaching 34.4 mm, while the arch foot again exhibits the smallest displacement. Overall, the displacements in the surrounding rock of the C\({}_{1}\)d formation are greater than those in the D\({}_{3}\)zg formation, as shown in Figure 14.  
Figure 15 shows a radar map of the surrounding rock displacement distribution at different monitoring sections. The starting position (0\({}^{\circ}\)) corresponds to the right arch shoulder, 90\({}^{\circ}\) corresponds to the arch top, and 270\({}^{\circ}\) corresponds to the arch bottom. The displacement of the surrounding rock around the C\({}_{1}\)d formation (monitoring section X) is larger, and the deformation area is wider, while the displacement of the surrounding rock around the D\({}_{3}\)zg formation (monitoring section Y) is mainly concentrated near the vault region--specifically, the left side of the vault (105\({}^{\circ}\)) and the midpoint between the right arch shoulder and the arch top (45\({}^{\circ}\)). The minimum displacement in the D\({}_{3}\)zg formation is 6.7 mm. The maximum displacement near the arch top on the left side (105\({}^{\circ}\)) is 30.2 mm, which is 23.5 mm greater than the minimum. Similarly, the maximum displacement at the midpoint between the right arch shoulder and the arch top (45\({}^{\circ}\)) is 29.5 mm, 22.8 mm greater than the minimum. Therefore, it is essential to pay close attention to localized large-deformation areas during construction and to implement appropriate support measures if necessary.  
The above analysis shows clear differences in the displacement field distribution of surrounding rock when the roadway crosses different formations. In the C\({}_{1}\)d formation, deformation is more widespread; in the D\({}_{3}\)zg formation, it is concentrated near the arch. The displacement is significantly affected by lithological differences. Additionally, greater deformation is observed in the harder formations near the stratigraphic boundary than in other regions of the same formation. This may be because the relatively softer formation near the boundary produces larger displacement and exerts compressive stress on the  
Figure 14: Displacement curves of characteristic monitoring points of surrounding rock at different locations.  
harder formation, forming a displacement anomaly zone near the boundary. The arch top area shows particularly pronounced displacement, as indicated in Figure 14. When combined with the distribution of the abnormal stress zone, it is evident that the vault region near the stratigraphic boundary should be a key focus during construction.