Tailings and Mine Waste Conference

Slurry to soil clay behaviour model : using methylene blue to cross the process / geotechnical engineering divide Wells, Patrick Sean; Kaminsky, H. A. W.


The models and formulae used to describe the behaviour of materials vary based on the history of the individuals and groups who defined the area of study. In the case of tailings behaviour, two main disciplines describe either end of the processes with very little in the way of common descriptors to bridge the base scientific and engineering principles. Process Engineering dominates the descriptions for tailings materials in their suspended solids or liquid slurry state. Based on various incarnations of rheology, including terms such as viscosity or yield stress, as well as material and chemical descriptors such as clay content, particle specific gravity, pH, and ionic concentration, all contribute to a well-defined behaviour model. Geotechnical Engineering dominates the descriptions for the same materials, once they have dewatered sufficiently to be described by the Terzaghi principle. Terms such as effective stress, pore water pressure, permeability, and coefficients of consolidation are used to monitor and predict the behaviour of these materials once deposited. Tailings engineering straddles these two disciplines and practitioners need to be fluent in both descriptions. However, these two areas do not readily translate and there are many cases where similar terms actually provide very different meaning (“water content” being one prime example). One area which could bridge the gap for clay-dominated tailings is through the methylene blue index (MBI) measurement and its clear correlation to rheology / strength, as well as correlations to liquid and plastic limits. This paper uses data from tailings in the oil sands of northeastern Alberta, Canada to show the relationship between MBI and the gradual transition from slurry to soil.

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