Centrifuge modelling of river embankments on homogeneous and layered subsoil

In the present context of climate change, the frequency of floods has increased, and their consequences are exacerbated by growing urbanization. Consequently, river embankments are recognized as strategic structures, crucial for safeguarding human activities against flood events and for the virtuous management of territories. Given their significant length, their variable geometrical and geotechnical properties, the irregular characteristics of the foundation subsoil, the assessment of the stability of river embankments requires the application of reliable and realistic methods. The response of a river embankment to hydraulic loads is strongly influenced by the hydromechanical properties of the soils constituting its body and the subsoil stratigraphy. This paper presents the results of four centrifuge tests aimed at investigating two specific aspects that could significantly affect the embankment's response: i) variations in the levee's degree of saturation due to changes in water content, induced by soil-atmosphere interactions and fluctuations in water levels; ii) the presence of a sandy layer hydraulically connected to the river in the foundation subsoil, potentially leading to the development of uplift pressures or piping beneath the toe, ultimately causing the embankment to fail. Centrifuge tests were conducted on small-scale embankment models characterized by trapezoidal-shaped cross-sections and constructed using a compacted silty clayey sandy mixture. These embankments were placed either above a fine-grained foundation layer or a layered subsoil consisting of a shallow fine-grained stratum overlying a highly permeable sand layer, directly connected to the river. To monitor the model's response to the imposed hydraulic boundary conditions, the middle section of the embankment was instrumented with miniaturized tensiometers, pore pressure transducers, and displacement sensors.