Effect of extraction water chemistry on the self-weight consolidation of oil sands fine tailings

CIM Journal, Vol. 2, No. 1, 2011

W. G. Miller, J. D. Scott and D. C. Sego

As part of an overall study of properties and processes influencing consolidation of oil sands fine tailings resulting from different extraction processes, self-weight consolidation tests were performed. Fourteen 2 m and 1 m high standpipe tests were instrumented to monitor the rate and magnitude of consolidation of seven fine tailings materials. Tests provided valuable information about the variation of consolidation related to differences in fine tailings material properties that result from a change in bitumen extraction process (caustic versus non-caustic). In addition, the effect of adding a coagulant to caustic fine tailings was measured. Test results are presented and discussed in terms of consolidation rate, long-term volume decrease, compressibility, and downward drainage. Non-caustic fine tailings had faster initial consolidation, which is important in tailings ponds for reducing storage capacity and returning decant water at a faster rate to the extraction plant. Similar results were obtained for caustic fine tailings with a coagulant addition. However, long-term settlement of the different fine tailings appears to converge to a similar value over time because it is then governed by effective stress.

Keywords: Oil sands, Fine tailings, Compressibility, Hydraulic conductivity, Consolidation, Large strain, Volume decrease, Settlement, Effective stress, Sodium adsorption ratio