Class A predictions for centrifuge modelling of uplift induced instabilities of river embankments

Flood events caused by the collapse of water-retaining earthworks are recognized as one of the most impactful natural disasters, affecting both urban and rural environment, as well as society and economy. The understanding of the peculiarities of different failure mechanisms is crucial for explaining the causes of breaching and assessing the safety of both new and existing earth infrastructures, under different hydraulic loading scenarios. This paper investigates the potential instability of the landside slope induced by high uplift pressures beneath the toe of a river embankment. This complex failure mechanism is largely influenced by the stratigraphy of the foundation soil and it might occur when embankment is constructed on alluvial plains with silty or clayey blankets overlying sandy soil strata, which act as preferential flow channel between the water basin and the landside. Results of a numerical predictive study carried out with the finite element method (FEM) on an unsaturated river embankment model, characterized by this peculiar subsoil layout, are presented and discussed. The impact of different thickness of the fine-grained layer on the potential failure mechanism has been evaluated, showing that this mainly affects the onset time of failure and the hydrometric level associated with its triggering. The analyses here presented provided fundamental insights for the design of a physical model test in a centrifuge.