Insulation covers with capillary barrier effects to control sulfide oxidation in the Arctic

Abstract

Insulation covers can be used for the reclamation of tailings storage facilities located in the Arctic. However, this approach can be vulnerable to changes in climatic conditions as its long-term performance is based strictly on controlling the temperature of tailings. A more robust alternative could be the use of insulation covers with capillary barrier effects because they control both the tailings temperature and oxygen flux. This study assesses the potential for an insulation cover with capillary barrier effects using laboratory tests and a field experimental cell. Material characterization indicated that the fine-grained compacted waste rock is a suitable material for constructing a moisture-retaining layer. A 2 m thick field experimental cell was constructed in which temperatures and unfrozen volumetric water contents were monitored for 3.5 years. Results showed thaw depths periodically reaching the reactive tailings and temperatures at the tailings–cover interface greater than 0 °C for 39–57 days each year. The degree of saturation in the moisture-retaining layer was almost always greater than 80%–85% when temperatures at the tailings–cover interface exceeded 0 °C. Yearly oxygen fluxes passing through the moisture-retaining layer were calculated to be less than 2 mol/m2/year, thus confirming the effectiveness of the cover as an oxygen barrier.