Settlement of Existing Structure Due to Construction of a Tunnel in Layered Soil

Metro construction in congested urban areas often involves the excavation of new tunnels. Tunnel construction induces the ground settlement above and the prediction of greenfield settlement is well established for homogeneous soil conditions and can be estimated using semi-empirical or numerical modeling. This paper investigates the influence of ground surface settlement caused by tunnel construction in layered soil on existing structures using numerical modeling. The numerical modeling has been done by keeping the soil condition similar to the actual scenario with multi-layered soil like clay, silt and sand. The numerical method is validated by comparing it with the field settlement values. The study illustrates the results for two varying parameters such as the centre-to-centre distance between tunnel and loading of structure. The results show that the effect of tunnelling on the foundation lies within two times the tunnel diameter from the centre line of the tunnel and the displacement beneath the foundation increases with increasing the surcharge.