Numerical issues in modelling DCM column-supported embankments featuring post-yield strain-softening : 2D simplified vs 3D models

The conversion of three-dimensional (3D) column-supported embankments into two-dimensional models based on the equivalent area approach (2D-EA) has been discussed in the literature. However, no study has been conducted yet considering deep cement mixing (DCM) columns undergoing post-yield strain-softening governed by plastic strains in columns. Therefore, in this paper, above issue is discussed considering 2D-EA and 3D finite element models, simulating the column behaviour using an extension of the Mohr-Coulomb model (EMC), which can simulate softening beyond yield as a function of plastic deviatoric strain. Results show that the performance predicted by the 3D and the 2D-EA models are significantly different if the same strength degradation model simulating softening is assigned to the EMC model in 2D-EA and 3D finite element models. Hence, a method is proposed to quantify the parameters for the EMC model when converting a 3D field embankment into a 2D-EA model or vice versa.