Abstract

Helical piles are increasingly adopted as deep foundation elements where rapid installation, limited site disturbance, and resistance to axial and lateral actions are required. Their response can, however, be affected by nearby excavation because removal of soil changes the stress field and produces lateral ground deformation. This study experimentally examines the response of model helical piles subjected to excavation-induced ground movement. Laboratory tests were performed in a 1 m × 1 m × 0.75 m steel tank containing poorly graded sand. Model piles were positioned at clear distances of 2d, 3d, and 4d from a simulated retaining wall, and excavation was carried out incrementally. Pile-head movement was monitored using a dial gauge. Single-, double-, and triple-helix configurations were considered, together with H/D ratios of 2.5 and 3.5. The observations indicate that pile-head deflection increases as excavation progresses and becomes more pronounced when the pile is positioned closer to the excavation boundary. Increasing the pile-to-excavation distance reduces the imposed lateral movement, while greater embedment and multiple helices improve resistance to ground deformation. The results demonstrate the combined influence of pile geometry and excavation proximity and provide practical guidance for preliminary assessment of helical pile foundations adjacent to excavation works. Keywords— helical piles, ground movement, excavation, pile deflection, H/D ratio, retaining wall, lateral soil movement, foundation engineering