Combining Geophysical Techniques (Eri, Ip, Tdem and Gpr) for the Characterization of Mining Waste

In old abandoned mining districts, waste materials were accumulated without prior sealing of the substrate, so there is currently a significant risk of contamination of soils and surrounding waters. In recent years, some of these mining dams have undergone a reclamation and sealing process to alleviate this problem. The current work analyses the efficiency of the characterization of these structures with different geophysical techniques and their use in monitoring the effectiveness of the isolation performed. This research was carried out in the old mining district of Linares-La Carolina (southern Spain), and electrical resistivity imaging (ERI), induced polarization (IP), ground penetrating radar (GPR) and time domain electromagnetic method (TDEM) techniques were used.The combination of ERI and IP made it possible to characterize the internal structure of abandoned mining dams, defining the geometry of these deposits and assessing the potential risks they entail. In addition, percolation zones of mining leachates were detected that indicate defects in the sealing stage.The TDEM technique was a good complement to the two previous techniques in terms of calculating the depths to detect the bedrock on which the mining dam is located. Regarding GPR techniques, while the research depth reached is scarce for any of the frequencies of antennas used (100, 250 and 500 MHz), this technique is useful since it provides detailed information of the last stages of filling, as well as being able to characterize the encapsulation performed during sealing.