Seismic Performance of Tehran Metro Tunnels Reinforced with Steel Fiber Reinforced Concrete under Manjil and Mexicali Earthquakes: A Finite Element Analysis

This study analyzes the seismic behavior of Tehran metro tunnels reinforced with Steel Fiber Reinforced Concrete (SFRC) under the influence of two distinct seismic events, Manjil and Mexicali earthquakes. For this purpose, ABAQUS software and the Finite Element Method (FEM) were used to accurately simulate the tunnel behavior and assess the impact of seismic forces. Two primary indicators, von Mises stress and displacement, were quantitatively analyzed to compare the performance of SFRC with conventional concrete under different seismic loads. The quantitative findings show that SFRC significantly reduces both stress and displacement. Specifically, under the Manjil earthquake, SFRC reduced von Mises stress by 25% and displacement by 18% compared to conventional concrete. Similarly, in the Mexicali earthquake, SFRC reduced von Mises stress by 22% and displacement by 15%. These results indicate that SFRC performs significantly better than conventional concrete, especially in critical areas such as joints and corners, which typically experience higher deformation during seismic events. Additionally, the study introduces the use of a hybrid fiber mix of micro and macro steel fibers, which improves stress distribution and deformation control. This combination of fibers provides superior performance compared to single-fiber SFRC models, and the optimized fiber distribution had a significant effect on reducing stress and displacement. The findings of this study demonstrate that SFRC substantially improves the seismic resistance of tunnel linings and provides valuable insights for optimizing tunnel design under seismic loads. Further research is needed to explore the long-term durability of SFRC and the soil-SFRC interaction under real seismic conditions.