Deformation and Force Numerical Analysis of Deep Foundation Pit in Soil-Rock Dualistic Stratum

Based on the finite element calculation software Plaxis, the numerical simulation of the deep foundation pit of the Nanjing Metro Engineering Second-Bridge-Park Station was carried out. The calculation results were in good agreement with the monitoring values of the surface settlement 5m away from the foundation pit as well as two typical horizontal displacement of the pile, indicating the reliability of the model. The model was used to analyze the soil deformation, surface settlement, pile displacement and pile stress in the soil-rock combination stratum. The results showed that the pile deformation mainly occured in the soil part in the deep foundation pit of soil and rock combination stratum. Moreover, the maximum displacement was below the middle part of the soil part; the maximum surface settlement was located 0.35H away from the pile (H was of excavation depth); the sudden change of the pile body was basically at the boundary between the soil and the rock as well as the bottom part of the pit, which showed that the deformation of the foundation pit of the soil-rock combination stratum was closely related to the thickness of the soil layer and the excavation depth of the foundation pit. Numerical simulation using Plaxis software could provide a proof for the design and construction of foundation pits.