Numerical tool for prediction of sand boil reactivations near river embankments

The article presents a three-dimensional (3D) finite element (FE) model of the groundwater flow beneath a river embankment, aimed at developing a simple and reliable numerical strategy for the identification of hydraulic conditions that cause the reactivation of sand boils in flood defense systems prone to recurrent backward erosion piping. The seepage model is calibrated on a cross section of the Po River, where a large natural sand boil has been periodically observed during past high-water events. Monitored river water levels, piezometric measurements, and geotechnical testing data have been used for the calibration study. The numerical analysis proposes a suitable way to simulate a preexisting eroded zone, identifies the key parameters to be collected in the field, and discusses the criteria for the assessment of piping reactivation. The sensitivity analysis proposed herein enables one to identify the set of model parameters capable of capturing field evidence.