Evaluation of oil sands thickened tailings consolidation and shear strength parameters using 3 geotechnical testing techniques

Authors: Kabwe, LK; Wilson, GW; Barsi, D Download Paper Open access courtesy of:

DOI https://doi.org/10.36487/ACG_repo/2655_03

Cite As:
Kabwe, LK, Wilson, GW & Barsi, D 2026, 'Evaluation of oil sands thickened tailings consolidation and shear strength parameters using 3 geotechnical testing techniques', in AB Fourie, M Horta, M Oliveira & S Wilson (eds), Paste 2026: Proceedings of the 28th International Conference on Paste, Thickened and Filtered Tailings, Australian Centre for Geomechanics, Perth, pp. 1-14, https://doi.org/10.36487/ACG_repo/2655_03



Abstract:
The stability of a tailings dam depends upon the strength of the tailings. Approximately 1.3 billion cubic metres of mature fine tailings (MFT) from Canadian Oil Sands mines are stored in tailings dams. The MFT need to be treated to achieve solids contents and strengths sufficient to support dams’ reclamation. Thickening is one of the potential technologies for converting MFT into a material with sufficient strength to support trafficability. Characteristics that can be reasonably investigated at the design stage, and may contribute to foundation failure, include shear strength, compressibility and permeability. In this research, these 3 characteristics for thickened tailings (TT) were evaluated using the large strain consolidation with shear strength (LSC-SS), consolidated-drained direct shear (CD-DS), and consolidated-undrained triaxial (CU-TR) testing techniques. The TT tested had a high sand content of 61% and exhibited dense sand behaviour. The characteristic stress–strain curve showed a peak stress at a relatively low strain and, thereafter, the stress decreased. Results showed that the TT was less compressible with a compression index Cc of 0.04. The hydraulic conductivity K decreased by one order of magnitude (i.e. 10-8 to 10-9 m/s) as the void ratio decreased from 1.3 to 0.92. The LSC-SS technique provided an effective friction angle (') value of 19.3°. The CU-TR and CD-DS tests provided effective friction angle (') values of 36 and 46°, respectively. These 2 values of ' confirmed that the TT behaved as a dense sand. The LSC-SS test that uses the vane shear device yielded a lower value of ’ due to various factors, including the rotation rate, vane insertion disturbances, and vane shape which destroyed the fabric and decreased its ’ value. The reconstituted and consolidated TT sample had a low effective cohesion (c’) value of about zero. The results of the strength parameters, compressibility, and K are crucial in any stability analyses of slopes against failure and landslides.

Keywords: large strain consolidation, direct shear, triaxial testing, angle of internal friction, cohesion

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