Piled-supported embankment responses to tunnelling in soft ground: An investigation of settlement and load transfer mechanisms

The escalation in infrastructure such as highways and high-speed railways has necessitated construction on soft and compressible ground, prompting the adoption of innovative solutions like piled-supported embankments. With the surge in tunnelling for transportations projects, the necessity of constructing tunnels in close proximity to piled embankments has become apparent. This study examines into settlement and load transfer mechanisms in piled-embankments affected by tunnel excavation at varying depths relative to pile lengths, employing a hypoplastic model to capture the nonlinear behaviour of soft soil. The findings indicate that the deepest tunnel caused the largest settlement, while the shallowest tunnel in led to the smallest settlement in the embankment due to pile settlements playing a significant role. The pile-soil stress ratio near the tunnel increased significantly when excavated close to pile shaft, contrasting substantially with decreased ratio in the tunnelling beneath the piled-embankment case. The bending moments in the piles exhibited differing behaviours in each case, with distinct trends observed in lateral movement and stress-induced responses. The axial load changes were influenced by factors such as negative skin friction, positive shaft resistance, and embankment weight transfer through arching, leading to unique load patterns along the pile length caused by the shallowest tunnel.