Introduction: The increase in population and traffic in metropolitan areas has led to the development of underground transportation spaces. Therefore, the estimation of the surface settlement caused by the construction of underground structures should be accurately considered. Several methods have been developed to predict tunneling-induced surface settlement. Among these methods, artificial intelligence-based methods have received much attention in recent years. This paper is aimed to develop a model based on Gene Expression Programming (GEP) algorithm to predict surface settlement induced by mechanized tunneling. Methods: For this purpose, Tehran Metro Line 6 was simulated numerically to investigate the effects of different parameters on the surface settlement, and 85 datasets were prepared from numerical simulations. Subsequently, several GEP models were implemented using the obtained datasets from numerical simulations and finally, a model with 30 chromosomes and 3 genes was selected as the optimum model. Results: A comparison was made between obtained maximum surface settlements by the proposed GEP model and numerical simulation. The results demonstrated that the proposed model could predict surface settlement induced by mechanized tunneling with a high degree of accuracy. Conclusion: Finally, a mathematical equation was derived from the proposed GEP model, which can be easily used for surface settlement prediction.

In some subsurface urban development projects, bedrock faults intersecting with the tunnel path are inevitable. Due to the high costs of urban tunnel projects, it is necessary to study the behavior of such concrete structures under fault movement risks. Using an advanced 3D numerical finite difference code and a plastic hardening constitutive model for the soil, this paper examined the performance of the straight and oblique segmented structures of Tabriz Subway Line 2 under large deformations. The Tabriz Line 2 tunnel passes through a reverse fault called the Baghmisheh Fault. The fault–tunnel simulations were validated by centrifuge tests on the segmental tunnel for normal faulting. In the centrifuge tests and validation models, there was a maximum difference of 15%. According to the results of the Tabriz Line 2 tunnel under reverse faulting, segmental structures outperform no-joint linings when it comes to fault movement. During reverse fault movement, line 2 segments did not collapse but showed slight deformations. However, continuous structures collapsed under faulting, i.e., the structural forces created exceeded the section strength capacity. Among the segmental structures, the lining with oblique joints showed better behavior against faulting than the lining with straight joints. For better tunnel performance under fault movement, oblique joints should be used in segmental structures in faulting areas.

Background: Nowadays, the construction of urban tunnels for rapid transportation in metropolises is necessary. Since these tunnels are excavated at low depths, they are often associated with different problems and hazards. Some of them can reduce the efficiency of the tunnel boring machines and sometimes will stop the project. Among these problems the clogging can cause problems at the cutter head, in the chamber, and in other sections where the material transference occurs. Objective: The main purpose of this paper is to evaluate and determine the risk of clogging in the tunneling boring machine in Line 6 of the Tehran Metro. It includes stations: Amirkabir, Shohada Square, Emam Hossein Square and Sayyadeh Shirazi. This phenomenon induces an adhesion of the shield with the soil, increasing the necessary shear forces and it can eventually leads to the project interruption. Methods: Due to the fact that the criterion for the behavior of fine soils against moisture is Atterberg Limits, therefore, Atterberg Limits and the water content were utilized. For this purpose, the new method proposed by Hollman and Thewes (2013) was used. In this study, in addition to the Atterberg limits, the amount of free water resulting from the machine and from the underground water inflow was included in the calculations. Results: It was found that the water content should be increased carefully as the soil is very sensitive to this parameter. An increase of 15% of the water content permits to reduce the risk of clogging. If the added free water amount 15%, the probability of clogging becomes high. Whereas, in case where the added free water amount reaches 20%, the risk of clogging decreases significantly. Conclusion: According to the performed assessments, it was found that critical areas for the clogging aspect are both the cutter head and the chamber. The sensitivity of the soil is very important to the free water amount. Therefore, due to the behavior of sticky and plastic of clay soils against increasing water, it is necessary to determine the percentage of allowable water used in mechanized excavation projects.