Geotechnical properties of centrifuged oil sand fine tailings

The main objective of this study was to determine the geotechnical properties of centrifuged oil sand fine tailings for surface deposition. A material with 60% solids (e = 1·5) was obtained using a bench-scale centrifuge. The fine-grained material (52% clay fraction) with a moderate water adsorption capacity (w _l = 40% and w _p = 20%) indicated an air entry value of 1000 kPa and a residual suction of 30 000 kPa. The correct way of representing the soil water characteristic curve for tailings was found to be the one based on degree of saturation along with simultaneous volume change measurements. The tailings mainly dewatered during normal shrinkage while remaining saturated whereas volume reduction was negligible beyond the shrinkage limit. Likewise, dewatering under an effective stress of 160 kPa was found to be 67% along with a compression index of 0·36. The saturated hydraulic conductivity measured 3 × 10⁻¹⁰ m/s that decreased marginally during consolidation and rapidly (10⁻¹⁰ to 10⁻¹⁸ m/s) due to suction application.