Diffused arching in embankments supported by non-compliant columns with capping beams

Abstract

A column-supporting system for embankments on soft soils is analyzed using the Finite Element Method. The numerical problem has boundary conditions similar to that of a trap-door, but, contrary to the classical trap-door studies, the focus in this paper is on the load transfer to the supporting columns measured by the system efficacy, and on the critical embankment height that prevents differential settlements on the embankment surface. The stress state simulated in the embankment rapidly evolves in the first stages of the soft soil settlement, measured by millimeters, but the changes to the elastic–plastic stress field developed are marginal in the subsequent stages of settlement simulated up to 10 cm. The displacement field in low embankments with a height comparable to the column spacing is dominated by the failure mechanism with shear bands reaching the embankment crown, causing differential settlements on the embankment surface. In higher embankments, the failure mechanism is confined to the lower portion of the fill, and no differential settlements were detected on the embankment surface. It was suggested that a hypothetical diffused soil arch formed above the failure mechanism, with a shape approximately following the principal stress trajectories. This conjecture was made based on the presence of elevated stress along the symmetry plane of the embankment-column periodic cell. Numbers related to system efficacy and critical height are reported for a limited set of model parameters, but the qualitative outcome of the study is likely applicable to a wider variety of embankments.