One of the large-scale field waste rock experiments (test piles) conducted as part of the Diavik Waste Rock Project was deconstructed, providing a spatially located set of geochemical, mineralogical, and particle-size distribution samples. Geostatistical analyses were conducted for sulfur and carbon content and saturated hydraulic conductivity, which affect the geochemical evolution of waste rock, to investigate the spatial dependence of these parameters. Analyses included population statistics, experimental semi-variogram estimation, and theoretical semi-variogram fitting. Population statistics were calculated for additional data sets from samples collected during the construction of the test piles. The population statistical analyses indicated that log-normal distribution provided the best fit for all investigated data sets. Experimental semi-variograms were estimated for the spatially located data set (test pile deconstruction) using the classical estimator, and theoretical semi-variograms were fitted. This investigation showed that the spatial distribution of sulfur, carbon, and hydraulic conductivity within the core of the test-pile experiments can be approximated using a log-normal distribution with a mean and standard deviation calculated using the samples collected during construction of the piles, and that little to no spatial relationship was present for these parameters at the scale of sampling. That the saturated hydraulic conductivity of the matrix material can be represented by the same statistical distribution throughout the test pile is significant because water flow, as well as mineral surface area and reactivity are dominantly controlled within the matrix portion of the test pile. Reactive transport simulations are included to demonstrate the influence of the matrix material on effluent geochemistry.

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.