Combined Geophysical Surveys for the Characterization of a Reconstructed River Embankment

The characterization of earthen and concrete river embankments plays a pivotal role in the hydrogeological risk assessment and is typically carried out with techniques that provide only punctual information (e.g., visual inspection, geotechnical soundings, etc.) In order to improve the extension and the completeness of the characterization procedure, applied geophysics provides several methods that, moreover, are also non-invasive, cost-effective and rather quick to use. In this work, we consider a 100-meter long river embankment located in the Veneto region (north-eastern Italy), reconstructed after its collapse due to an extreme rain event in 2010. This artificial levee consists of a bouldering structure hosting a jet-grouting wall in the central part that still does not assure an appropriate embankment waterproofing. Therefore we combined electrical resistivity tomography, multi-channel analysis of surface waves, and ground penetrating radar to investigate the heterogeneities of both the reconstructed and the natural parts, as well as the mechanical properties of the grouting wall. The results show this inner septum as a relatively conductive mean with evident discontinuities, which can be related to the infiltration phenomena taking place. Finally, our outcomes are validated thanks to several geotechnical soundings.