Centrifuge Modeling of Stability of Embankment on Soft Soil Improved by Rigid Columns

Earth platforms supported by rigid columns provide an effective solution for embankments founded on thick deposits of soft soils. Nevertheless, the failure mechanisms and associated soil–structure interactions remain inadequately comprehended, particularly for structures such as columns with caps or ground beams. Recent studies have reported sporadic incidents of basal instability in rigid column–supported embankments over soft soil. To gain further insight into this issue, this study investigated the foundation settlement, failure mode of rigid columns, and ground stability under staged embankment construction by centrifuge model tests. Different ground improvement schemes (head conditions) are compared, including columns, capped columns, and columned ground beams, along with natural ground as a base model. Test results show that the potential slip surfaces for embankments on soft ground are almost circular in shape, with or without capped column support. Rigid columns exhibit different failure modes across the improved domain: compression failure under the crest, bending failure under the shoulders, and tensile/bending failures near the toe. Under critical conditions, the columns near the toe collapse first, followed by the adjacent columns beneath the slope and center of the embankment. In contrast, the column failure sequence is unclear for the beam scenario. Capped columns were found to reduce the foundation displacement significantly. Given equivalent area coverage ratios, columned beams demonstrate greater efficacy in controlling ground deformation than capped columns. The interconnecting beams form a strong foundation that mitigates overstressing of subsoil, thus reducing differential and final settlements. Finally, the stability of the ground reinforced with rigid columns under embankment loading is discussed, taking into account the fracturing of columns and the function of caps and ground beams.