Abstract: Time-effect exists in the process of deep excavation due to the creep property of soft soil.In this article, the excavation process of a deep excavation in Ningbo city is simulated using SSC model and finite element software PLAXIS,and the deformation characteristics of retaining structures and deep excavation are analyzed.Results revealed that the horizontal displacement of diaphragm wall, ground settlement and inner force of retaining structure increase with the increasing of construction time; while the rheological effect of foundation upheaval is not obvious. Secondly, the positions of the maximum horizontal displacement of diaphragm wall correspondingto various construction stages shift towards the deep with the increasing of excavation depth. However, the maximum ground settlement at different construction stages almost happens about 10m away from the pit wall. On this basis, an equation is established between cumulative maximum ground settlement and cumulative construction time.Moreover, curves of the bending moment and shear force of diaphragm wall vs.excavation depth at different construction stages are identical and display S-shape.Finally,support structure simpede the further development of the horizontal displacement of diaphragm wall and the ground settlement. The deformation of supporting structures and the sharp change of internal force could be effectively controlled by applying support in time. The conclusions offer guidance to the construction of deep excavation in Ningbo city to ensure the safety of construction process.

Key words: soft soil of Ningbo city, numerical simulation, time-effect, deep excavation, creep