An integrated geophysical approach for water infiltration detection and characterization at Monte Cotugno rock-fill dam (southern Italy)

Abstract

This study concerns with an integrated geophysical approach for the detection and spatial-temporal characterization of the water infiltration into the Monte Cotugno dam embankment. This strategic civil infrastructure is the largest rock-fill dam in Europe and represents the nodal point of the water system feeding the Basilicata, Puglia and Calabria regions (southern Italy). Here, we propose an approach based on the combination of geophysical techniques as Ground Penetrating Radar (GPR) and Electrical Resistivity Tomography (ERT) with Thermal-InfraRed mapping (TIR) and geotechnical in-situ measurements. Such an approach was applied for the diagnosis of the Monte Cotugno dam with the aim both to gain information about the geometry of visible micro-fractures in the dam coverage and have a rapid mapping of the dam inner areas affected by water infiltration phenomena. The sensing methods were deployed in a cascade modality, where the Thermal-InfraRed (TIR) method was used for surveying the dam along the overall length in order to achieve information about the dam coverage status. In particular, TIR analysis allowed us to identify five areas affected by significant fractures and coating detachment. Afterwards, GPR surveys were performed on the sloping side of the dam by investigating few areas among those identified by TIR analysis. In this way, it was possible to get indications whether the water infiltration affected the deeper parts of the dam. Lastly, Electrical Resistivity Tomography (ERT) method was applied in order to detect deeper inner areas affected by water leakages. Finally, a joint interpretation of the three sensing methods was confirmed by shallow boreholes (<20m) drilled over the dam crown, which have evidenced the presence of localised water leakages in the dam. In conclusion, the results are encouraging and the integrated use of non-invasive sensing techniques can be considered an effective tool for the diagnosis and short- and long-term monitoring of critical infrastructures as the Monte Cotugno dam.