Effect of soil Young’s modulus on Sub-rectangular tunnels behavior under quasi-static loadings

Tunnels are an important component of the transportation and utility system of cities. They are being constructed at an increasing rate to facilitate the need for space expansion in densely populated urban areas and mega-cities. The circular and rectangular tunnels cannot completely meet the requirements of underground space exploitation regarding the cross-section. Sub-rectangular tunnels are recently used to overcome some drawbacks of circular and rectangular tunnels in terms of low utilization space ratio and stress concentration, respectively. However, the behavior of the sub-rectangular tunnels under seismic loading is still limited. This need to be regarded and improved. This paper focuses on conducting a numerical analysis to study the behavior of the sub-rectangular tunnels under seismic loadings. Here seismic loadings in this study are represented by quasi-static loadings. Based on the numerical model of the circular tunnel that was validated by comparison with analytical solutions, the numerical model of the sub-rectangular tunnel is created. This paper is devoted to highlight the differences between the behavior of the sub-rectangular tunnels compared with the circular ones subjected to quasi-static loadings. The soil-lining interaction, i.e., full slip and no-slip conditions are particularly considered. The influence of soil’s Young’s modulus on the sub-rectangular tunnel behavior under quasi-static loading is also investigated. The results indicated that soil’s Young’s modulus significantly affects static, incremental, and total internal forces in the tunnel lining under quasi-static loadings. Special attention is a significant difference in total internal forces in the sub-rectangular tunnel lining in comparison with the circular tunnel ones and the stability of the lining tunnel for both the full slip and no-slip conditions when subjected to quasi-static loadings.