Soil disturbance effects of pile-reinforced metro foundation subjected by tunnelling beneath: field investigation and model tests

Urban roadbed foundations reinforced by piles are inevitably influenced by the construction of tunnels underneath. Investigating the soil disturbance effects of shield tunnelling on pile-reinforced foundations is essential for ensuring the safety of upper structures. In this paper, a micro shield tunnelling apparatus was developed to replicate the tunnelling procedure on a scale-reduced model of a pile-reinforced foundation. The law of soil disturbance effects of the tunnel was examined based on in-situ field investigation and model tests. The field investigation results indicate that the excavation of the tunnel results in additional soil settlement, and the ground settlement took a V-shaped profile first and shifted to a W-shaped profile eventually. Model tests on soil settlement show that increasing the pile-tunnel distance helps mitigate the impacts of tunnel excavation, and the reduction of soil stress during construction around the tunnel increased with a greater pile-tunnel distance. The results contribute to the prevention of excessive deformation induced by shield tunnelling beneath roadbed supported by pile-soil composite foundations.