2D-Electrical Resistivity Imaging for Sike Survey: Impact of the a Priori Information Management

In France, EDF (Électricité De France) is in charge of managing the large hydraulic structure stock dedicated to producing hydroelectricity. This responsability is associated with high economical and safety issues. Electrical Resistivity Imaging (ERI) is being widely used on earth embankment dikes, either for extensive survey of large sections (a few km) or for higher resolution surveys on shorter sections (a few 100m). However, the processing of extensive longitudinal survey with conventional 2.5D software is likely to yield image artefacts. This study aims to show that a bad management of the dike complexity in the inversion process is the origin of these artifacts. To overcome this limitation, a new inversion algorithm specially created to take into account the complex behaviour of the dike is presented. This development aims at filling the gap between more classical 2D and purely 3D approaches, by optimising a compromise between acquisition cost and model reliability. Applied to real data sets this tool supplies a new understanding of the interpretation capability of the inversion results.