The electrical resistivity tomography method in the detection of shallow mining cavities. A case study on the Victoria Cave, Cartagena (SE Spain)

Former mining areas which have been under intensive mining activity raise some geotechnical concerns. The main concerns that can arise are, for example, foundation problems on buildings placed on these mining areas, and the damage to roads resulting in potholes. These are due to the collapse of the mining cavities from natural alteration processes during the course of time. In order to check its reliability, the electrical resistivity tomography (ERT) method was tried out on a selected area of La Sierra Minera, where the location and orientation of the main caves are well known. This technique was chosen because the climate of the study area is semi-arid and the cave space is occupied by air, so the electrical resistivity contrast between the cave itself and the host rock could be expected to be high. The geophysical results have shown a close correlation with the position of known caves but further have highlighted the position of new cavities previously unknown before employing the ERT method. The discovery has been corroborated by speleologists' inspection of the area. The ERT method has therefore proved to be very effective and suitable in providing sufficient subsurface information on shallow cavities.