## 4 Summary of the Project and Preprocessing of Data
### Determine Risk Grade  
According to Formulas (15) and (16), the closeness degree of the tunnel section to different risk levels is calculated and standardized, so as to establish an evaluation system. To validate the reliability of the enhanced variable weight matter-element extension model, a comparative analysis was conducted with both the standard matter-element extension model and the fuzzy comprehensive evaluation method. The corresponding findings are presented in Table 11.  
According to Table 11, the risk level of sections K1#, K2#, K3#, and K4# is \(V_{1}\) (ideal state). Although they are in an ideal excavation condition, it is still necessary to prepare for potential risks during construction. Sections K5# and K6# have a risk level of \(V_{2}\) (low-risk state), where the surrounding rock has a significant impact on excavation construction. To reduce risks, necessary support measures and drainage work should be implemented. The use of HW150 system arches (0.45 m) with steel reinforcement and embedded grouting pipes at collapse areas can help form a closed structure as soon as possible. Sections K7# and K8# have a risk level of \(V_{3}\) (medium-risk state) due to their location in fractured segments. However, with proper support and initial lining, normal construction can still be carried out. Similarly to sections mentioned earlier, HW150 system arches with steel reinforcement  
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Fixed**} & \multicolumn{8}{c}{**Variable Weight**} \\ \cline{3-10}  & & **Weight** & \(\mathbf{K_{1}}\)**\#** & \(\mathbf{K_{2}}\)**\#** & \(\mathbf{K_{3}}\)**\#** & \(\mathbf{K_{4}}\)**\#** & \(\mathbf{K_{5}}\)**\#** & \(\mathbf{K_{6}}\)**\#** & \(\mathbf{K_{7  
should be used for support along with embedded grouting pipes at collapse areas to form a closed structure promptly. During excavation construction, the possibility of sudden water influx or collapse risks should be considered based on changes in weightage and fuzzy evaluation criteria. Early detection work should be conducted in advance to mitigate these risks.  
Based on the actual excavation conditions of sections KS 260 + 052 to KS 262 + 835, the joint and fracture development in the surrounding rock of sections, \(\text{K}_{1}\text{\#}\) and \(\text{K}_{2}\text{\#}\) is relatively minor. The overall integrity of the surrounding rock is good during TBM excavation, leaning more towards \(V_{1}\) grade (ideal state). However, the standard expandable model lacks adaptability when facing changes in indicators and is not sufficiently relevant to risk assessment issues. In contrast, sections \(\text{K}_{3}\text{\#}\) and \(\text{K}_{4}\text{\#}\) have no joint or fracture development in the surrounding rock, with mostly dry rock walls and high stability of the tunnel cavity. Under certain circumstances without considering other factors, it can be considered an ideal excavation environment.  
Sections \(\text{K}_{5}\text{\#}\), \(\text{K}_{6}\text{\#}\), on the other hand, are affected by structural compression and hydrothermal alteration. They exhibit significant folding, strong carbonization, developed rock cleavage, and slight surface spalling during TBM construction. However, the fuzzy comprehensive models used do not consider coupling effects resulting from changes in multiple risk indicators, which deviates from reality.  
Sections \(\text{K}\text{\#}\) and \(\text{K}_{8}\text{\#}\), influenced by faulted fractured zones, show poor integrity of surrounding rocks with intense weathering and strong carbonization of rocks. The interlayer bonding is weak, with loose rocky material prone to fragmentation. During the TBM excavation process, severe block falling occurs along with local structural face collapse phenomena in some areas.