Geotechnical-geophysical investigations in the Mbuji-Mayi region, Congo

An Electrical Resistivity Tomography (ERT) survey was carried out in the Mbuji-Mayi region in the south-central part of the Democratic Republic of the Congo to investigate the lithology and compactness of the underground geological formations at a future drinking water-treatment plant site. From two ERT profiles, high resistivity values were observed in the upper layer up to several hundred Ω⋅m, which was correlated with the uppermost soil layer and dry sands. In the deeper layers, the resistivity values decreased to tens of Ω⋅m, indicating the notable presence of a sandy layer with water content, rather than basement materials, as was expected. In addition, some lateral variations along the profile lines were observed, which are thought to be related to the heterogeneity of the sand mineralisation content and the degree of water infiltration due to different porosities of the sands. This information is in good correlation with previous geotechnical survey data and drillings in the area. For each ERT profile, we describe the general conditions of the geological formations, as inferred from the geotechnical survey data and two-dimensional images of inverted apparent resistivity presented as true resistivity images. The findings of this study are expected to serve as supporting material in order to correlate with future studies.