Numerical investigation on the effect of initial water content on dynamic responses of unsaturated sandy and clayey embankments

High water contents and poor compaction during construction have been reported to cause severe embankment damage during earthquakes. In this paper, a fully coupled soil-water-air finite element method is adopted to reveal the failure mechanism of unsaturated embankments subjected to earthquakes. And the dynamic responses of sandy and clayey unsaturated embankments with different water contents and dry densities are carefully investigated. It is found that the sandy embankments compacted above the optimum water content (OWC) during construction have a sliding potential triggered by liquefaction during earthquakes, while the sandy embankments compacted at or below the OWC only show slight subsidence due to the contribution of suction to soil strength. The stability of the clayey embankments worsens with increasing water content. The clayey embankments with a high water content exhibit substantial subsidence at the crest and bulging at the laterals, which are different from the failure mode of sandy embankments during earthquakes. •The seismic behavior and failure mechanism of unsaturated embankments are investigated by soil-water-air fully coupled finite element analysis.•The influences of initial water contents and compaction qualities on the dynamic responses of embankments are discussed.•The different failure modes of sandy and clayey embankments are examined.