Each year hydraulic structures such as levees and earth dams are hit by disorders that can lead to their collapse. A dike reinforcement method such as the deep soil mixing gets interest for its reinforcement capacity at moderate cost. We report on the use of a non-destructive technique to effectively assess the proper achievement of these structures and their evolution in time. More particularly, 2D-electrical resistivity imaging (2D-ERI) was used to assess a cut-off wall. We evaluate the benefits and limitations of three acquisition techniques (longitudinal, transversal and cross-hole). To complete the interpretation, we performed a comprehensive geotechnical study to make a diagnosis of the structure. Each inversion result is combined with numerical modelling that enlightens limitations of the acquisition techniques and improve the interpretation. Results show that 2D-ERI can present a real benefit for the assessment of cut-off walls even if the dimensions of the cut-off wall limit the detectability of deep heterogeneities.