Influence of train-induced dynamic loading on deformation of deep excavations adjacent to elevated railways

With the rapid expansion of urban rail transit, ultra-deep excavations adjacent to existing elevated railways are increasingly common, posing significant challenges to deformation control and operational safety. This study investigates the dynamic response of a deep foundation pit adjacent to an operating elevated railway. A three-dimensional finite element model was developed in ABAQUS, incorporating soil–structure interaction and staged excavation. A Fortran-based DLOAD subroutine was used to simulate bidirectional, double-track train loads via time-history half-wave sinusoidal functions. The influence of dynamic loading on retaining wall deformation, basal heave, and ground settlement was systematically analyzed and validated against field monitoring data. The results indicate that dynamic loading significantly amplifies deformation, with the top displacement of the retaining wall increasing by approximately 50% compared to static conditions (from 3.98 mm to 6.17 mm), while the maximum deformation shows a moderate increase of 4.2% (from 12.56 mm to 13.08 mm). Surface settlement exhibits a groove-shaped distribution, with peak settlement at about 0.53 times the excavation depth from the pit edge and increasing by up to 49% under dynamic loading (from about 2.4 mm to 3.6 mm at points C and D). The proposed approach demonstrates good agreement with field data and provides a practical framework for analyzing excavation–infrastructure interaction under cyclic loading.