Numerical Insights into Tunnel Excavation Effects on Pile-Supported Embankment in Soft Clay: A Comparison Between Consolidated and Unconsolidated Conditions

This study examines the influence of adjacent tunnel excavation on pile-supported embankment in soft clay under both unconsolidated and long-term consolidated conditions. A comprehensive three-dimensional numerical model was developed to simulate the coupled hydro-mechanical interaction between the embankment, piles, and surrounding ground. The soft clay behaviour was described using a hypoplastic constitutive model enhanced with intergranular strain theory to capture stress-dependent stiffness, dilatancy, and degradation under loading. Three tunnel alignments relative to the pile foundation alongside the pile shaft (S), near the pile toe (T), and beneath the pile toe (B) were analyzed to evaluate deformation and load transfer mechanisms. Results indicate that tunnelling induces significant differential settlements, with maximum values of 0.49%, 0.20%, and 0.45% for Cases S, T, and B, respectively. Consolidation substantially reduced both surface and pile settlements while improving subgrade stiffness and load-carrying performance. The maximum bending moment in the leading pile reached 142 kNm at Z/Lp = 0.56 under unconsolidated conditions and decreased following consolidation. The findings highlight the critical role of tunnel depth and consolidation state in controlling deformation, stress redistribution, and structural safety of pile-supported embankment during tunnelling activities.