Geotechnical-geochemical and operational considerations for the application of dry stacking tailings deposits – state-of-the-art

Abstract

Filtered tailings (FT) deposition is experiencing a worldwide growing application as a potential alternative to overcome several constraints associated with land use and fresh water availability in areas near mining operations. Implementation of FT deposition can significantly reduce the volume of the tailings dam; the result is a lower impact on the project development area compared to conventional slurry and thickened tailings deposits. Furthermore, the associated costs and the physical and environmental risks, during both the overall tailings disposal operation and closure, may be significantly reduced. Water and land use can be reduced not only in arid to semiarid regions, where the FT technology is currently being applied, but also in rainy regions. A comprehensive study of the implementation of the FT technology is required because of two major issues: (1) project development areas characterised by total annual rainfall higher than 1,000 mm and seismic activity higher than 8 Mw, and (2) very fine tailings types generated in the mine process plant. These factors push geotechnical-geochemical engineering knowledge to the limit and make the industry develop novel technologies for tailings filtration and transportation to meet new necessities. This paper presents geotechnical-geochemical considerations, including the rheological, thickening, filtering, and desiccating tailings characteristics obtained through an extensive laboratory testing program. The testing program examines a number of key parameters: the density and moisture requirements for the FT compaction, the criteria for the required area for the FT deposition for its subsequent compaction, criteria to meet the long-term physical and chemical stability during the FT disposal operation and closure, and the associated water management plan. This paper also describes experience regarding the criteria for the selection of FT equipment and transportation systems, their implementation and operation, and the operation and management of the FT deposit as a whole. Finally, future trends of FT applications associated with both the new generation of tailings filtration and transportation systems and the combined application of other tailings disposal technologies, such as the co-disposal of tailings and mine waste, are discussed.