Abstract: The engineering application of present calculation methods for foundation pit’s springback deformation is limited due to a large number of required parameters and cumbersome calculation process. In this paper, the ratio of plastic deformation to total soil compression deformation was defined as the plastic development coefficient β, and on this basis, a new practical estimation method for the springback deformation was proposed. The expression of β can be deduced by the relationship between void ratio and compression deformation. The calculated depth of rebound soil can be estimated according to the influence of unloading ratio R on springback deformation. Ignoring the spatial effect of soil stress distribution in the center of deep foundation pit, and assuming that the gravity stress field of central pit bottom soil is uniform before and after excavation, we hence obtained the calculation method. The method was used to calculate the central springback deformation of a foundation pit (depth 17.9m) in Shanghai. By comparing calculated results with monitoring data, this method was proved to be feasible, and recommendations of prediction correction and engineering application were given.

Key words: soft soil, springback of foundation pit, loading and unloading of soil, plastic development coefficient, rebound deformation