# Interaction of Segmental Tunnel Liniings and Dip-Slip Faults--Tabriz Subway Tunnels
## 5 Conclusions  
In order to gain a better understanding of the behavior of segmental tunnels in the face of normal and reverse fault movement, a 3D advanced numerical simulation was carried out. This research is distinguished by accurate details of segment joint modeling and an advanced soil constitutive model. To confirm the power of finite-difference numerical codes for the subject under study, centrifuge tests conducted by one of the co-authors were used ([PERSON] et al. [2; 12]). In addition, a real-life case of a segmental tunnel facing a reverse fault on the Tabriz Metro line 2 was studied. Based on the results presented herein, the segmental lining at the intersection with the dip-slip fault (normal and reverse fault) has acted effectively. The ability to withstand and reduce a large part of the fault force and a major part of the lining failure is limited to the opening of transverse and longitudinal joints. The results can be resumed as follows:  
* Normal faults intersecting with segmental linings have tensile rupture mechanisms, and segmental lining joints undergo greater deformations and openings than reverse faults. It has been observed that as the tunnel depth increases, the degree of separation of segmental rings, the opening of longitudinal joints, and the severity of failures increase, while the range affected by the fault in segmental lining declines, and the breakage and opening of joints approach the fault line, as a result. Vertical displacement and tunnel rupture rates increase dramatically as the slope angle of the fault increases, and the rupture path tends to follow the footwall as the fault slope increases. * The function of the segmental tunnel in the reverse fault was compressive. Thus, unlike normal faults, it will not suffer extensive damage. As a result of reverse faulting, the segmental lining experiences smoother displacement along the entire tunnel length, and only undergoes limited deformation and opening of longitudinal and transverse joints. Furthermore, segmental linings with oblique joints perform better than straight joints. In comparison to straight joint linings, they have less displacement and their internal force, including bending moments, extends to a smaller area. The maximum ground displacement value increases gradually with increasing tunnel overburden in a normal fault. The vertical displacement of the ground also increases with an elevation of the fault angle. This is due to an increase in the vertical component of the fault force. Through a decrease in the fault slope angle, the fault area is further developed towards the footwall, and further affects the surface. * Comparing the performance of segmental and continuous lining at the intersection with the reverse fault, it can be concluded that, unlike segmental lining, continuous tunnel lining in interaction with the fault suffers sudden failure at the fault line. The displacements were concentrated at the fault line location due to the rigidity of the continuous tunnel lining. Consequently, the probability of rupture and failure of the continuous tunnel lining at the intersection with the fault is high. In addition, the majority of the fault force is transmitted to the tunnel lining in the hanging wall. In a continuous lining, the bending moment is about twice as great as in a segmented lining, and the normal force is ten times as great. This research received no external funding. Not applicable. Data Availability Statement:Requests for all types of data used to support the findings of this study, after the publication of this article, will be considered by the corresponding author. The authors wish to express their gratitude to the Auckland University of Technology (AUT), New Zealand, for their collaboration in confirming the modeling aspects of this study using the academic license of the FLAC3D Version 7.00.139 software provided by the Itasca Consulting Group, Minneapolis, MN, USA. Thanks also to [PERSON] and [PERSON] for their guidance in modeling the segment joints of the tunnel lining.