Analysis on the mechanical behavior of the influence of deep excavation in soft soil on ground surface settlement

Combined with the common estimation method for the ground surface settlement, an analysis was conducted on the ground surface settlement and the retaining structure of a deep excavation in a subway station of Ningbo soft clay area, and the influences on the ground surface settlement produced by the construction technologies, including excavation during construction, reinforcing the supporting stiffness and changing the mechanical behavior of soil, were discussed. Based on a comparison, it is concluded that appropriately increasing the supporting stiffness at the early stage of excavation may be benefitial to reducing the ground surface settlement, and timely treating with the passive zone at the bottom of retaining wall is helpful to reduce the deformation of the wall. Strengthening the 3 m depth at the bottom of retaining structure by deep concrete mixing method may effectively control the ground surface settlement. Deep excavation is a dynamic construction process. During the construction process, the maximum settlement point gradually goes far away from the retaining wall consistently with a distance of the excavation depth for each step and finally stabilizes within the range of the excavation depth. During the construction, it is recommended to continuously adjust the control objective and monitor dynamically to ensure the safety of surrounding environment.