Research on dynamic response analysis of foundation pit support structure in complex soil layers under earthquake action

Abstract China’s location at the confluence of the Pacific and Eurasian seismic belts leads to frequent and intense seismic events, making seismic design essential for deep excavation projects. Although the pile-anchor support system is widely adopted in such contexts due to its economic and construction advantages, existing research lacks systematic evaluation of its seismic performance, and design codes offer limited guidance specifically addressing seismic conditions. To address this gap, this study employs finite element numerical simulation and theoretical analysis to examine the seismic behavior of reinforced concrete single-row pile supports. The main findings include: (1) Increasing pile spacing from 1.5 m to 2.4 m leads to a moderate increase in maximum horizontal displacement (on the order of 3%–6%) and a slight extension of the concrete damage zone under seismic loading; (2) enlarging the pile diameter from 1.2 m to 1.8 m slightly reduces the maximum lateral displacement of the piles (by about 2%–4%), but more noticeably improves the damage state of the concrete, indicating that increasing pile diameter mainly enhances local damage resistance rather than significantly changing overall deformation; (3) raising the concrete grade from C25 to C40 substantially enhances the overall stiffness of the support system, reducing the maximum horizontal displacement by approximately 5%–14% and significantly mitigating flexural damage and damage concentration near the pile head. These results demonstrate that parameter optimization—particularly of concrete grade and pile spacing—plays a critical role in enhancing seismic performance. This study provides quantitative insights to inform the seismic design of pile–anchor support systems for deep excavations in complex soil conditions.