Time-dependent deviation of high-speed railway bridge pier-cap-pile foundations in deep soft soils under surcharge loads: a case study

Abstract

Permanent surcharges or temporary surcharges along high-speed railway lines occur frequently due to irregularities in construction, resulting in lateral deviations of adjacent pier-cap-pile foundations, especially in soft soil areas. The pier-cap-pile foundation deviation caused by surcharge loads in soft soils shows a significant time-dependent characteristic (TDC) that has been disregarded in most previous studies. In this study, an extended Koppejan model, which considers the TDC of soil movements, was developed, and the corresponding user-material subroutine (UMAT) was programmed in ABAQUS software. Then, the UMAT was embedded into a finite element model that was combined with an actual engineering case. Based on the validated model, the time-dependent deformation development of the pier-cap-pile foundation was investigated, and the subsequent service performance and deformation mechanism characterized by the time-dependent additional load were revealed. In addition, a rectification measure with an unloading + high-pressure rotary jetting pile was proposed, and the pile foundation performance after rectification was evaluated. The evaluation results were successfully applied to field rectified construction. The research findings obtained in this study may provide a valuable reference for similar accidents of pile foundation deviation caused by adjacent surcharge loads.