A study was conducted to evaluate the properties and processes influencing the rate and magnitude of volume decrease and strength gain for oil sand fine tailings resulting from a change in bitumen extraction process (caustic versus non-caustic) and the effect of adding a coagulant to caustic fine tailings.
Laboratory flume deposition tests were carried out with the objective to hydraulically deposit oil sand tailings and compare the effects of extraction processes on the nature of beach deposits in terms of geometry, particle size distribution, and density. A good correlation exists between flume deposition tests results using oil sand tailings and the various other tailings materials. These comparisons show the reliability and effectiveness of flume deposition tests in terms of establishing general relationships and can serve as a guide to predict beach slopes.
Fine tailings were collected from the various flume tests and a comprehensive description of physical and chemical characteristics of the different fine tailings was carried out. The characteristics of the fine tailings is presented in terms of index properties, mineralogy, specific surface area, water chemistry, liquid limits, particle size distribution and structure. The influence of these fundamental properties on the compressibility, hydraulic conductivity and shear strength properties of the fine tailings was assessed. Fourteen two meter and one meter high standpipe tests were instrumented to monitor the rate and magnitude of self-weight consolidation of the different fine tailings materials. Consolidation tests using slurry consolidometers were carried out to determine consolidation properties, namely compressibility and hydraulic conductivity, as well as the effect of adding a coagulant (calcium sulphate [CaSO4]) to caustic fine tailings. The thixotropic strength of the fine tailings was examined by measuring shear strength over time using a vane shear apparatus.
A difference in water chemistry during bitumen extraction was concluded to be the cause of substantial differences in particle size distributions and degree of dispersion of the comparable caustic and non-caustic fine tailings. The degree of dispersion was consistent with predictions for dispersed clays established by the sodium adsorption ratio (SAR) values for these materials. The biggest advantage of non-caustic fine tailings and treating caustic fine tailings with coagulant is an increased initial settlement rate and slightly increased hydraulic conductivity at higher void ratios. Thereafter, compressibility and hydraulic conductivity are governed by effective stress. The chemical characteristics of fine tailings (water chemistry, degree of dispersion) do not have a significant impact on their compressibility behaviour and have only a small influence at high void ratio (low effective stress). Fine tailings from a caustic based extraction process had relatively higher shear strengths than comparable non-caustic fine tailings at equivalent void ratios. However, shear strength differences were small and the overall impact on consolidation behaviour, which also depends on compressibility and hydraulic conductivity, is not expected to be significant.
| Identifer | oai:union.ndltd.org:LACETR/oai:collectionscanada.gc.ca:AEU.10048/1497 |
| Date | 11 1900 |
| Creators | Miller, Warren Gregory |
| Contributors | Chalaturnyk, Richard (Civil and Environmental Engineering), Scott, J. Don (Civil and Environmental Engineering), Sego, David C. (Civil and Environmental Engineering), Wong, Ron (Civil Engineering, Univeristy of Calgary), Gupta, Rajender (Chemical and Materials Engineering), Joseph, Timothy (Civil and Environmental Engineering), Chalaturnyk, Richard (Civil and Environmental Engineering), Scott, J. Don (Civil and Environmental Engineering), Sego, David C. (Civil and Environmental Engineering) |
| Source Sets | Library and Archives Canada ETDs Repository / Centre d'archives des thèses électroniques de Bibliothèque et Archives Canada |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | 5778969 bytes, application/pdf |
| Relation | Miller, W.G., Scott, J.D., & Sego, D.C. (2009). Flume deposition modeling of caustic and noncaustic oil sand fine tailings. Canadian Geotechnical Journal, 46. 679-693, Miller, W.G., Scott, J.D., & Sego, D.C. (2010). Influence of the extraction process on the characteristics of oil sands fine tailings. CIM Journal, 1 (2), 93-112, Miller, W.G., Scott, J.D., & Sego, D.C. (2010). Effect of extraction water chemistry on the consolidation of oil sands fine tailings. CIM Journal, 1 (2), 113-129, Miller, W.G., Scott, J.D., & Sego, D.C. (2010). Influence of extraction process and coagulant addition on thixotropic strength of oil sands fine tailings. CIM Journal, 1 (3), Miller, W.G., Scott, J.D., & Sego, D.C. (2011). Effect of extraction water chemistry on the self-weight consolidation of oil sands fine tailings. CIM Journal, 2 (1) |
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