Choice of Soil Constitutive Models in Numerical Analysis of Foundation Pit Excavation Based on FLAC3D

The selection of soil constitutive model is very important in numerical analysis of foundation pit excavation. In the process of foundation pit excavation, the stress path of soil in different areas is different. And the stress path has a significant influence on the mechanical parameters of soil. Therefore, the selected constitutive model should be able to reflect the influence of stress path. FLAC3D 6.0 embeds directly usable hardened soil model and small strain hardened soil model, which expands the application range of the numerical method in geotechnical engineering. Based on FLAC3D, the applicability of common soil constitutive models including linear elastic model, Mohr-Coulomb (MC) model, hardened soil (HS) model and small strain hardened soil (HSS) model for foundation pit engineering are studied. It is founded that the linear elastic model is not suitable for the analysis of foundation pit excavation. MC model has poor applicability for shallow foundation pit excavation, but the increase of excavation depth improves its applicability in some extent. HS model and HSS model can reasonably describe the deformation of surrounding soil and supporting structure in the process of excavation, and HSS model can consider the elastic nonlinearity in the small strain range, hence the numerical results are closest to the measured results. The results can provide a theoretical basis for selecting a reasonable constitutive model for foundation pit engineering numerical analysis based on FLAC3D in the future.