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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.
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Formation of a Dispersed Soil Arch in Embankments Supported by Columns with Cap Beams and the Development of System Efficacy
The process credited for high efficacy of embankment pile support systems is the formation of soil arches in the embankment fill. The specific system considered in this presentation is one with cap beams over rows of columns inserted through soft clay to support an embankment fill. Such a system lends itself to a two-dimensional analysis. A formation of distinct arches, as conjectured in many design approaches, was not confirmed. However, based on the calculated stress distribution and the major principal stress trajectories, one can identify “dispersed” arches spanning the distance between two neighboring cap beams. The dispersed arching was not identified in low embankments, whereupon the settlement of the soft soil, a collapse mechanism propagated through the entire embankment height causing differential settlement of the embankment crown. This study was focused on the efficacy of the pile support system and on better understanding of the mechanisms behind the differential settlement at the crown of the embankment.
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- Award ID(s):
- 1901582
- PAR ID:
- 10402308
- Date Published:
- Journal Name:
- Geo-Congress 2022 GSP 336
- Page Range / eLocation ID:
- 221 to 230
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Conference Paper:
- https://doi.org/10.1061/9780784484067.023
