Comprehensive geotechnical and geochemical characterisation of two diamond ore tailings

The physical and chemical stability of tailing deposits sometimes have conflicting priorities, yet they are rarely examined congruently comprehensively. This paper presents an investigation of the combined geotechnical and geochemical behaviours of two samples of diamond ore tailings. Detailed basic and advanced geotechnical laboratory characterisation tests were conducted to evaluate the particle size distribution, hindered sedimentation, compressibility, hydraulic conductivity and undrained shear strength of both tailings. Furthermore, duplicate specimens to evaluate the drainage effluent’s geochemical compositions were conducted to evaluate the compliance with regulatory concentration criteria. The cation and anion concentrations of the expelled water were analysed at different consolidation stages, along with other basic geochemical index properties such as pH, redox potential and electrical conductivity. Both the geotechnical large strain consolidation testing and geochemical pore fluid collection were performed in a controlled-temperature environment to represent the cold climatic regime at the mine site. Tests were performed in a walk-in freezer with a nominal ambient temperature of 4–5°C. Moreover, the drainage effluent from the large-strain consolidation geochemical duplicates was collected using an innovative sampling system that ensured that the sample was not exposed to the atmosphere. The geotechnical and geochemical implications of both tailing treatments are discussed.