Comparative Analysis of Load Transfer Behavior in Piled versus Geosynthetic Encased Column Embankment Models

Abstract

Significant progress has been made in understanding load transfer mechanisms in piled embankments reinforced with geogrids. However, knowledge remains limited regarding foundations incorporating semi-rigid supports, such as encased granular column. This study compares the performance of granular base layers in embankments supported by concrete piles and granular encased columns. Physical modelling with transparent soils and digital imaging techniques were employed to investigate mechanisms that are otherwise inaccessible through conventional experimental methods. A transparent sand was used to simulate the granular base, while transparent synthetic clay formulated with Laponite RD® represented the underlying soft soil. Settlements, deformation patterns and load transfer mechanisms are analyzed using Digital Image Correlation (DIC). Results indicate that piled embankments with rigid supports exhibit significantly lower vertical displacements than those with semi-rigid columns. However, differential settlements were higher in GRPS models due to their greater stiffness compared to encased granular columns. The mobilization of tensile forces by geosynthetic reinforcement was found to be directly associated with differential settlements between the supports and the soft soil. Incorporating geogrid as geosynthetic reinforcement in the granular layer was observed to effectively mitigate settlements in both GRPS and GRCS embankments, each through distinct mechanisms.