Two and Three-Dimensional Modeling of DM Columns under Embankments

Abstract

Deep mixed (DM) columns have been commonly used to increase bearing capacity of soft soil and reduce total and differential settlements of embankments. In most analyses (especially numerical analyses) of embankments over DM columns, two-dimensional models are commonly used for simplicity. However, it is not clear how well the two-dimensional (2D) models represent the behavior of embankments over DM columns that are typically installed in a three-dimensional (3D) pattern, such as a square or triangular pattern. In this study, 2D and 3D numerical analyses were conducted to show the comparisons of their results including maximum settlements and vertical stresses. In the 2D analysis, individual DM columns and the soil between these columns are converted to several DM walls parallel to the centerline of the embankment. The DM walls are assumed to have equivalent moduli or strength averaged from the individual DM columns and the soil between these columns based on their areas and moduli or strengths. The comparisons show that the 2D model calculates slightly (conservatively) larger maximum settlements at the base of the embankment than the 3D model if the DM walls/columns are within the elastic limit. However, the 2D and 3D models produce very different results of vertical stresses on the top of DM walls/columns.