Influence of extraction process and coagulant addition on thixotropic strength of oil sands fine tailings

This study used 6 different oil sands fine tailings derived from 2 extraction processes to determine the influence of extraction processes on the thixotropic gain in strength of fine tailings. In this study, fine tailings derived from the Clark hot water extraction (CHWE) process were referred to as caustic, while fine tailings from the OSLO hot water extraction (OHWE) process were referred to as non-caustic. The influence of adding a coagulant to caustic fine tailings was also examined. The properties and processes influencing the rate and magnitude of volume reduction and gain in strength for tailings produced using the causing and non-caustic extraction processes were evaluated. The 2 main components were flue deposition tests and tests for geotechnical properties of the fine tailings. The thixotropic strength of fine tailings at large void ratios manifested itself as a bonding or gel strength that can prevent initial consolidation or settlement of fine tailings. Differences between the fine tailings' thixotropic strength development were explained based on their physical and chemical characteristics. It was concluded that the different water chemistries of the 2 extraction processes were responsible for the different amounts of dispersion of the clay-shale seams present in oil sands ore, with less dispersed non-caustic fine tailings. 23 refs., 5 tabs., 7 figs.