Comprehensive geotechnical and geochemical characterisation of two diamond ore tailings

Abstract

Physical and chemical stability of tailings deposits sometimes have conflicting priorities, yet they are rarely examined congruently in a comprehensive research program. This paper presents an investigation of the combined geotechnical and geochemical behaviour of two samples of diamond ore tailings. Detailed basic and advanced geotechnical laboratory characterization 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 compliance with regulatory concentration criteria. The cation and anion concentrations of the expelled water were analyzed 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 the 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 the sample was not exposed to the atmosphere. The geotechnical and geochemical implications of both tailings treatments are discussed.