## 3 Frameworks and Methodologies for Research
### Methodologies for Research
#### 3.2.1 Risk Identification of TBM Construction Based on the WBS-RBS Method
The resulting decomposed structure for TBM construction risks obtained using the RBS method is depicted in Figure 3.  
Establishment of TBM construction risk identification coupling matrix  
According to the established Work Breakdown Structure (WBS) and Risk Breakdown Structure (RBS), the lower-level units of both structures are interconnected to derive the coupling matrix for identifying construction risks in TBM projects [25]. In this matrix, \"0\" signifies that there is no risk generated by the interconnection, while \"1\" indicates that a risk is generated. In constructing the coupling matrix, we first ensure that each item (\(W\)) in the WBS and each risk category (\(R\)) in the RBS are clearly identified. Then, by matching one by one,  
Figure 3: Decomposition structure diagram of TBM construction risk sources. we create a crossing point for each pair of \(W\times R\) that indicates whether \(W\) creates a risk during construction. For example, hazardous gas leakage is generated by the intersection of \"technical preparation \(W_{11}\)\" and \"tunnel depth \(R_{15}\), construction management status \(R_{31}\), security education situation \(R_{33}\)\", reflecting that the technical preparation caused by the tunnel burial depth is too large, the construction management is confused, and the safety education is insufficient, resulting in the occurrence of harmful gas, but non-timely feedback and solutions to the problem. The likelihood of accidents increases greatly. The outcomes of the TBM construction risk identification coupling matrix are presented in Table 1. Finally, the specific risks are as follows: (1) \(W_{11}\)\(R_{15}\), \(W_{11}\)\(R_{31}\), \(W_{11}\)\(R_{33}\): Hazardous gas leakage; (2) \(W_{12}\)\(R_{11}\), \(W_{12}\)\(R_{12}\), \(W_{12}\)\(R_{12}\), \(W_{12}\)\(R_{12}\), \(W_{12}\)\(R_{14}\), \(W_{35}\)\(R_{14}\): Rock blast; (3) \(W_{12}\)\(R_{12}\), \(W_{12}\)\(R_{13}\), \(W_{21}\)\(R_{13}\), \(W_{35}\)\(R_{13}\): Surging water; (4) \(W_{12}\)\(R_{14}\), \(W_{12}\)\(R_{15}\), \(W_{21}\)\(R_{11}\): Collapse; (5) \(W_{13}\)\(R_{22}\), \(W_{13}\)\(R_{23}\), \(W_{22}\)\(R_{21}\), \(W_{21}\)\(R_{22}\), \(W_{21}\)\(R_{23}\): Discontinuous slagging; (6) \(W_{14}\)\(R_{21}\), \(W_{14}\)\(R_{31}\), \(W_{14}\)\(R_{32}\), \(W_{14}\)\(R_{33}\): IBM jamming; (7) \(W_{21}\)\(R_{21}\), \(W_{21}\)\(R_{22}\), \(W_{21}\)\(R_{31}\), \(W_{21}\)\(R_{32}\), \(W_{21}\)\(R_{33}\): Support destabilization deformation; (8) \(W_{21}\)\(R_{41}\), \(W_{42}\)\(R_{42}\): Poor ventilation and dust collection; (9) \(W_{23}\)\(R_{21}\), \(W_{23}\)\(R_{22}\), \(W_{24}\)\(R_{21}\), \(W_{24}\)\(R_{22}\): Deviation of digging direction; (10) \(W_{31}\)\(R_{11}\), \(W_{31}\)\(R_{23}\), \(W_{31}\)\(R_{24}\), \(W_{31}\)\(R_{25}\): Cave collapse; (11) \(W_{32}\)\(R_{23}\), \(W_{22}\)\(R_{21}\), \(W_{21}\)\(R_{22}\): Water accumulated in the hole; (12) \(W_{31}\)\(R_{31}\), \(W_{31}\)\(R_{32}\), \(W_{33}\)\(R_{13}\): Lining leakage; (13) \(W_{41}\)\(R_{24}\), \(W_{41}\)\(R_{31}\), \(W_{41}\)\(R_{41}\)\(R_{42}\), \(W_{41}\)\(R_{43}\): Underground pipeline damage; (14) \(W_{34}\)\(R_{13}\), \(W_{34}\)\(R_{14}\), \(W_{21}\)\(R_{15}\), \(W_{44}\)\(R_{15}\): Deformation of surrounding buildings; (15) \(W_{21}\)\(R_{42}\), \(W_{13}\)\(R_{21}\), \(W_{13}\)\(R_{22}\), \(W_{44}\)\(R_{2}\): Stratigraphic ground settlement. Initially, a comprehensive evaluation is conducted to identify potential risks associated with TBM projects involving the construction of exceptionally long tunnels. This assessment follows a hierarchical structure model based on the fundamental principles of the analytic hierarchy process (AHP). The model comprises three layers: the target layer, criterion layer, and indicator layer, arranged in descending order of significance. The target layer represents TBM construction risk for ultra-long tunnels (\(U\)), while the criterion layer comprises \(U\) = [\(U_{1}\), \(U_{2}\), \(U_{3}\), \(U_{4}\)].