# Structural Stress Characteristics and Joint Deformation of Shield Tunnels Crossing Active Faults
## 3 Analysis of Segmental Tunnel Influenced by Fault Movement
### Mechanical Response of Segmental Tunnel
Figure 9: Shield tunnel deformation under normal fault dislocation. Some like +1.554e-01 means \(1.554\times 10^{-1}\). damage of the tunnel structure was slight, and the structure was in a safe state. When reverse faulting of 15 cm was imposed, the maximum compressive damage value of the tunnel structure was 0.32, for which the compressive concrete was in the stage of stiffness degradation, corresponding to the damage value. When fault dislocation reached 20 cm, the compressive damage value was 0.77, indicating that the tunnel structure suffered severe compressive damage at this time. When fault dislocation of 15 cm was imposed, the maximum tensile damage of the structure was only 0.06. When the fault movement reached 20 cm, the tensile damage of the structure increased sharply, and the maximum tensile damage value was 0.254. It can be observed that, under reverse faulting, the structural damage of the segmental tunnel was mainly located at the structural arch haunch, where the concrete is prone to suffer tensile and compressive damage, indicating that the tunnel structure at this time was mainly subjected to lateral force. Therefore, the tunnel segments are more likely to be collapsed under reverse fault displacement. Figure 11: Tensile damage distribution of the shield tunnel under reverse faulting: (**a**) under 10 cm fault displacement, (**b**) under 15 cm fault displacement, and (**c**) under 20 cm fault displacement. Some like +3.735e-02 means 3.735 \(\times\) 10\({}^{-2}\). Figure 12: Compressive damage distribution of shield tunnel under reverse faulting: (**a**) under 10 cm fault displacement, (**b**) under 15 cm fault displacement, (**c**) under 20 cm fault displacement. Some like +1.200e-01 means 1.2 \(\times\) 10\({}^{-1}\). By comparing the structural damage of the segmental tunnel subjected to fault dislocation, it can be found that when the normal fault dislocation was 15 cm, the shield tunnel structure had significant local damage. However, when reverse fault dislocation of 15 cm was imposed, the shield tunnel structure still had a certain bearing capacity. The main reason can be explained as follows. Compared with the lateral bearing capacity of the segmental tunnel, the circumferential joints were the weak part of the shield tunnel. When the normal fault occurred, the shield tunnel was first damaged at the circumferential joints. When the reverse fault occurred, the shield tunnel was mainly subjected to lateral force, and the stress and deformation of the circumferential joints were relatively small. Therefore, under the same fault displacement, the effect of normal fault displacement on the segmental tunnel was more significant than that of reverse fault displacement. The stress contours of the longitudinal and annular bolts subjected to the reverse fault dislocation are illustrated in Figure 5:0 When the fault dislocation reached 15 cm, the maximum stress of the annular bolts was 444.7 MPa and the maximum stress of the longitudinal bolts was 430.2 MPa, both of which were less than the bolt yield stress of 480 MPa. None of the bolts yielded at this time. Therefore, under reverse fault displacement, large tensile deformation of segmental joints rarely occurs.