Study on the impact of new pier cap construction on adjacent high-speed railway subgrades

With the rapid development of rail transit, construction activities near existing high-speed railway lines have become increasingly frequent. However, most studies focus on excavation depth while neglecting lateral proximity effects and the complete construction sequence. This study establishes a PLAXIS 2D model with the HSS constitutive model, validated against field data, to investigate the effects of new pier cap construction on adjacent high-speed railway subgrades. The model evaluates displacements of subgrade soil, retaining walls, and pile foundations, and explores the influence of construction distance. Results show that maximum displacement occurs at the uppermost edge closest to the excavation. Among construction stages, bored pile activation and dewatering excavation exert the greatest impact. Quantitative thresholds for safe construction distances are proposed: within 1.8 m, substantial impact; 1.8-12 m, significant; 12-60 m, minor; beyond 60 m, negligible.