Numerical Modeling of Lime-Cement Columns Using PLAXIS 2D and 3D

Sammanfattning

This thesis investigated numerical modeling of lime–cement column (LCC) reinforced embankments using PLAXIS 2D and PLAXIS 3D. For 2D, the Volume Averaging Technique (VAT) which is a homogenization method was used, in which thesoil was modeled using S-CLAY1S and the columns using the MNHard model. Theaim was to evaluate VAT in PLAXIS 2D for reproducing the behavior of the Nödingetest embankment with focus on Serviceability Limit State (SLS). In addition, twosimplified 3D analyses were conducted. One using the same material models as in theVAT for comparison between 2D and 3D and the other using the Concrete Model forthe columns to assess alternative, potentially less conservative modeling approaches.The study confirmed that the VAT is a practical and sufficiently accurate tool forserviceability analyses of LCC-reinforced embankments. This due to its efficiency,advanced constitutive models, and reliable settlement and pore pressure response.3D simulations captured transition zone and arching effects which was not includedin VAT. Besides this variation the comparison of the VAT and 3D revealed thatVAT is a simplification of a 3D problem in a 2D plane-strain model, but still witha very close accuracy.For column models, MNHard gave more stable and realistic settlements, while theConcrete Model produced more conservative larger settlements due to its drainagetype limitations. The concrete model however showed a high potential for capturingadditional column behaviors and failure mechanisms making it potentially interesting for Ultimate Limit State analysis (ULS).A limitation of this thesis was the lack of comprehensive laboratory data for calibrating the input parameters required for the numerical models. In addition, thecomparison between column models was limited by the lack of measured settlementdata, making it difficult to evaluate the accuracy of the Concrete Model.Suggestions for further work include strengthening the link between VAT and theSwedish method, analyzing deformation mechanisms, exploring VAT for ULS, improving the Concrete Model for LCC columns, and including creep effects for floatingcolumns.