Interaction between retaining wall and structural piles in soft soil-deep excavation

Purpose This study aims to investigate the structural interaction between retaining walls and structural piles in soft soil-deep excavation. Design/methodology/approach A comprehensive three-dimensional finite element model of a deep excavation in a 40 m thick soft soil layer was developed to evaluate the influence of this interaction on the lateral displacement and bending moment of the walls and piles. In addition, a parametric study was conducted to evaluate the effects of sheet pile retaining wall’s (SPRW) stiffness and diameter’s hollow spun concrete (HSC)-structural piles’ diameter on wall behaviors. Findings The outcome reveals that the presence of HSC-structural piles significantly alters the structural response of the SPRW. In the central zone of the excavation, lateral displacement and bending moment of the SPRW decreased by up to 25% and 15%, respectively. In addition, the horizontal displacement and bending moment of the HSC-structural piles decrease with increasing horizontal distance between the SPRW and piles. Notably, piles located near the excavation corners exhibit superior performance, with reductions of nearly 65%-80% in horizontal displacement and 60%-80% in bending moment compared to centrally positioned piles. Furthermore, the increasing SPRW stiffness reduces wall displacement but significantly increases the SPRW’s bending moment, while enlarging HSC pile diameter notably decreases wall displacement with minimal impact on the SPRW’s bending moment. Research limitations/implications The study focused solely on the interaction between retaining walls and structural piles in deep excavations in soft soil, with limited validation against field data. Originality/value This study provides a comprehensive evaluation of pile-wall interaction in soft soil-deep excavations – critical aspects that have often been overlooked in practical design and construction – thereby offering more effective strategies while mitigating the risk of collapse during excavation construction.