Application of the GPR and ERT methods for non-invasive examination of a flood dike

As part of the NAWA-EMMAT project, geophysical surveys were carried out on selected sites in Poland, i.e. on the flood dike and in the surrounding of the concrete water dam. The goal of the surveys was the non- invasive detection of loose zones in the flood dike and fractured zones located in the subsoil of the water dam. Terrain geophysical measurements were conducted with the use of electrical and electromagnetic methods as well as applying seismic methods. Due to the limitations of the length of this paper, only selected results recorded on the flood dike using selected geophysical methods, i.e. electrical resistivity tomography (ERT) and ground penetrating radar (GPR) are presented. The presence of several higher hydraulic permeability zones in the dike was suggested by the results of the ERT method. The GPR method allowed, due to its high resolution, to identify small leakage zones in the body of the dike. An attempt at a quantitative interpretation of the geophysical data was made; for this purpose, the synthetic results obtained from numerical modelling of electrical and electromagnetic fields were applied. For proper construction of numerical models and further interpretation, the results of geotechnical sounding, geological drilling and the results of petrophysical measurements were also used