2.5D Numerical Formulation for Analysing Long‐Term Settlement of Tunnel‐Soil System Induced by Cyclic Train Loading in Soft Soil Area

This paper presents an efficient two‐and‐a‐half dimensional (2.5D) numerical approach for analysing the long‐term settlement of a tunnel‐soft soil system under cyclic train loading. Soil deformations from train loads are divided into shear deformation under undrained conditions and volumetric deformation from excess pore water pressure (EPWP) dissipation. A 2.5D numerical model was employed to provide the dynamic stress state owing to the moving train load and the soil static stress state by the gravity effect for the determination of their accumulations. Then, an incremental computation approach combined with the initial strain approach in the framework of the 2.5D model was developed to compute the long‐term deformation of the tunnel‐soft soil system, considering the influence of the soil hardening due to EPWP dissipation. This approach helps to determine the distribution of the progressive settlement, transverse and longitudinal deformations in the tunnel‐soil system, overcoming traditional limitations. A comparison of settlements computed using this approach with measured settlements of a shield tunnel in soft soil shows good agreement, indicating the effectiveness of the proposed approach in analysing train‐induced progressive deformation of the tunnel‐soil system.