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

Abstract

This thesis investigated numerical modeling of lime–cement column (LCC) rein forced embankments using PLAXIS 2D and PLAXIS 3D. For 2D, the Volume Aver aging Technique (VAT) which is a homogenization method was used, in which the soil was modeled using S-CLAY1S and the columns using the MNHard model. The aim was to evaluate VAT in PLAXIS 2D for reproducing the behavior of the Nödinge test embankment with focus on Serviceability Limit State (SLS). In addition, two simplified 3D analyses were conducted. One using the same material models as in the VAT for comparison between 2D and 3D and the other using the Concrete Model for the columns to assess alternative, potentially less conservative modeling approaches. The study confirmed that the VAT is a practical and sufficiently accurate tool for serviceability 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 included in VAT. Besides this variation the comparison of the VAT and 3D revealed that VAT is a simplification of a 3D problem in a 2D plane-strain model, but still with a very close accuracy. For column models, MNHard gave more stable and realistic settlements, while the Concrete Model produced more conservative larger settlements due to its drainage type limitations. The concrete model however showed a high potential for capturing additional column behaviors and failure mechanisms making it potentially interest ing for Ultimate Limit State analysis (ULS). A limitation of this thesis was the lack of comprehensive laboratory data for cali brating the input parameters required for the numerical models. In addition, the comparison between column models was limited by the lack of measured settlement data, making it difficult to evaluate the accuracy of the Concrete Model. Suggestions for further work include strengthening the link between VAT and the Swedish method, analyzing deformation mechanisms, exploring VAT for ULS, im proving the Concrete Model for LCC columns, and including creep effects for floating columns.