Experience gained from the construction of earthfill dams and the unpleasant disasters concerning the artificial embankments have urged scientists, engineers and public authorities to develop methods for their characterisation and monitoring. Of these methods, the indirect geophysical techniques, especially the widely known spontaneous potentials (SP) method, have been used for the identification of seepage zones within the structure of the embankment (Merkler et. al., 1989). Although the method has proved to be highly cost-effective for locating seepage zones, it can't be taken into consideration due to the lack of reliable quantitative interpretations to estimate the depth of the anomalies. Among other techniques, the potentialities of employing the highly promising Geoelectrical Resistivity Tomography (ERT) can be explored to solve this kind of problems because resistivity data can be inverted to give more reliable models. These can be very useful both in characterising the embankment's internal structure and in monitoring the continuity of impermeable diaphragms, usually constructed to prevent/minimise piping, that could result in incalculable consequences. As concerning the first problem, ERT can aid in characterising the fine structure thus leading to the identification of the presence of loose and probably permeable zones. While in the second case, a specific approach can be developed to study the diaphragms either those made of bentonite or of reinforced concrete. In this paper, we present a case study conducted over part of an earth embankment along one of the effluents of the Po River (NE ltaly). The area is characterised by a recent cover of alluvial deposits with prevailing sandy silt sediments, alternated by low permeability clay levels. The geophysical survey comprised several ERT profiles carried out both parallel and perpendicular to the embankment's main axis to accomplish a final 3D model for the embankment itself and of the impermeable bentonitic diaphragm placed just near its upstream side (Fig. 1 ).


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