Analysis of weak points for dykes and dams
Case study: Geophysical and geotechnical investigation of dykes

Dykes must be judged related to its stability and hydraulic conditions. Therefore the building ground in the dyke body as well as in the area before and behind the dyke has to be investigated. The homogenous areas and weak points have clearly to be separated.

A suitable combination of geophysical and geotechnical investigations delivers the best solution of the problem. A 2D-geoelectrical measurement and the accompanying exploration by drillings is the best alternative for an exact survey of the underground conditions along dykes and dams.

The example of a dyke investigation in the area of middle Germany, with the resistivity depth section of a 2D-geoelectrical measurement at the upper part and the accompanying underground section at the lower part, is showed in the figure.

Homogenous areas, which are described in detail with the old drillings (BS) and the new ones (RKB), are separated in the result of the geoelectrical investigations. In the figure the information profit for the underground model, related to the geophysical investigation, is clearly discernible. The transition from the cohesive to the incoherent dyke body at station 9220 m is well visible by the sharp border between low (green-yellow colour) and high (red colour) resistivities and can be definitely interpreted.

The results of the underground investigations are the basis for the further hydraulic and stability analysis. The dyke conditions can be clearly analysed with these results and suitable redevelopment suggestions can be presented.

Our company has been successfully investigated more than 200 dyke kilometres with the combined geophysical-geotechnical investigation method since 2005.

Fig. 1: Vertical resistivity section after 2D inversion and longitudinal subsoil section