Preliminary evaluation of Speswhite kaolin as a physical analogue material for unsaturated oil sands tailings

ABSTRACT: Thin-lift deposition of treated oil sands tailings is currently investigated as a potential solution for creating a trafficable cap layer for future reclamation activities. To determine the optimal thickness of the cap layer, physical modeling experiments using the 50g-ton geotechnical beam centrifuge at University of Alberta were proposed. Prior to the deposition of fresh layers, the cap layer is often unsaturated due to freeze-thaw and atmospheric drying. In this paper, Speswhite kaolin is investigated as the candidate for a physical analogue of unsaturated oil sands tailings. Due to its high brightness and repeatability, Speswhite kaolin has been widely used as a modeling clay in geotechnical centrifuge experiments. However, its suitability of simulating unsaturated tailings with high clay content was rarely considered in the past. Two different sample preparation methods using Tempe cells and air-drying to create blocks of unsaturated Speswhite kaolin are evaluated. Undrained shear strength was measured by the miniature vane shear device and unconfined compression test while drained shear strength was determined by the direct shear device. Test results showed that the two materials behaved similarly in drained conditions while Speswhite kaolin exhibited a higher shear sensitivity in undrained conditions. Test results also showed different drying behaviour between the two materials: Speswhite kaolin dries faster, more uniformly and to a higher void ratio than treated oil sands tailings. Potential causes behind these observations are discussed in the paper.