Geotechnical profiling of a surface mine waste dump using 2D Wenner–Schlumberger configuration

Mapping the subsurface in slope stability analysis of disposal areas is difficult, especially the disposal layering materials that are assumed to be homogeneous instead of their real conditions. Moreover, the hoarding activities on high slope form layers based on the nature of the rock mechanics with large materials or boulders rolling down to the toe of the slope, while small ones are held at the top. Each layer formed, however, has certain geotechnical characteristics. The aim of this study is to determine the profiling of disposal material using a geoelectrical method known as Wenner–Schlumberger configuration with a line length of 450 m and also to find the resistivity value for mine waste materials based on an empirical number, which is a number that is obtained from the result reading compared to the actual condition in the field. The study was conducted on an in-pit dump with an estimated height of 150 m and a thickness of 50 m, and the data obtained were processed using RES2DINV software. The results showed that the subsurface cross-section has three layers consisting of bedrock with a resistivity of 50–70 Ωm, contact zone with 30–50 Ωm, and disposal material layer with 1–30 Ωm, which can be used for the slope stability analysis. This concept is very helpful for the geotechnical analysis on high mine waste dumps or sloping basement zone. This study focuses on the resistivity value for waste dump materials, which has not been clearly mentioned in the previous studies.

Characterization and Economic Potential of Historic Tailings from Gravity Separation: Implications from a Mine Waste Dump (Pb-Ag) in the Harz Mountains Mining District, Germany

In contrast to modern tailings from froth flotation, little is known about historic tailings from gravity separation. However, they may be of economic interest due to their higher metal grades compared to modern tailings. As an example for these types of historic tailings, the inner structure, as well as the economic potential (Pb, Zn, Cu, Ag, Sb), of the old Bergwerkswohlfahrt mine waste dump in Germany were studied. The investigations focused on textural, geochemical, and mineralogical properties. For this purpose, an extensive drilling program was undertaken. The drill cores were subsequently analyzed with a laser-induced breakdown spectroscopy (LIBS) core scanner to obtain the detailed spatial distribution of potentially valuable elements. The fine-sized residues could be differentiated into different layers, all of them including valuable metals in varying proportions. The strong variations in stratification and in metal distribution over short distances are caused by the batch-wise deposition of the tailings. This heterogeneity within short distances has to be taken into account for future exploration of these types of deposits. The application of a core scanner using LIBS is very convenient for detailed spatial analysis of drill cores, however, the calibration effort, particularly for heterogeneous sample material, is proportionally large. The valuable metal content for Bergwerkswohlfahrt was estimated to be 8000 metric tons of Pb and 610,000 ounces of Ag. Although of limited economic value, recycling might finance future remediation costs. Furthermore, the occurrence of historic tailings in nearby clusters may present further recycling opportunities.