Thomas Pabst

1. Large amounts of waste rock are generated by mining operations and are generally stored on the surface in piles or dumps [1–4]. Waste rock piles are constructed by repeatedly dumping waste rock ...

Explicitly modelling tailings consolidation behaviour contributes to improve integrated management approaches and accurately estimate the storage capacity of tailings storage facilities (TSFs) to better predict their static and dynamic stability. However, slurry tailings demonstrate a highly non-linear evolution of stiffness and hydraulic conductivity during consolidation, thus significantly complexifying the determination of their hydromechanical properties. In this study, an approach to update Mohr Coulomb parameters and simulate the continuous evolution of hydraulic conductivity and stiffness of tailings materials with the reduction of the void ratio was proposed and embedded in a finite difference code to more realistically simulate the evolution of material properties during sequential loadings. The model was validated using laboratory column tests and various predictive functions were tested to estimate hydraulic conductivity for field applications. Finally, the developed approach was applied to a simplified model of tailings impoundment to illustrate practical applications. Results from this study indicated that the approach developed was able to capture the non-linearity properties of tailings during consolidation, and that using continuously updated stiffness and hydraulic conductivity could induce significantly different magnitude and rate of consolidation than models with constant properties. Predictive models such as Kozeny–Carman and Kozeny–Carman Modified models also gave a satisfactory estimation of tailings behaviour, at least for preliminary studies. The simple modifications to the numerical codes proposed in this paper could therefore significantly improve the numerical simulation of tailings behaviour in the short term and contribute to a better planning of deposition plans.

Large amounts of waste rock are produced during mining operations and often disposed of in large piles. Particle size segregation usually occurs during waste rock disposal, which can lead to high variations of particle size distribution (PSD) along the pile slope, increasing the risk for hydrogeotechnical instabilities. Determining segregation in situ is, therefore, critical to implement control measures and optimize deposition plans. However, characterizing PSD at field scale remains challenging because of the large dimensions of the pile, the instability of the blocks and the steep slopes. In this study, images, covering a 1400 m wide and 10 m high section of a waste rock pile, were taken and analyzed using image analysis to characterize segregation along the slope of the pile. PSD curves in different sections along the slope were determined and the segregation degree and characteristic diameters (e.g., D₁₀, D₅₀, D_80,D₉₅) were quantitatively compared. Results allowed to quantify segregation along the vertical direction of the pile, showing that segregation degree increased from − 0.77 ± 0.39 in the top (finer zone) to + 0.4 ± 0.14 in the bottom (coarser zone). Significant lateral heterogeneity was also observed with maximum diameters varying between 80 and 180 cm in the bottom section. Such segregation and lateral heterogeneity could induce significant variations of waste rock properties, with, for example, hydraulic conductivities varying by more than 2 orders of magnitude within the pile.