Kabwe, LK, Kone, M, Sorta, A, Wilson, GW, Scott, JD & Ulrich, AC 2013, 'Measurements of unsaturated soil properties of old and new mature fine tailings', in M Tibbett, AB Fourie & C Digby (eds), Mine Closure 2013: Proceedings of the Eighth International Seminar on Mine Closure, Australian Centre for Geomechanics, Cornwall, pp. 159-170, https://doi.org/10.36487/ACG_rep/1352_14_Kabwe (https://papers.acg.uwa.edu.au/p/1352_14_Kabwe/) Abstract: The Geotechnical Centre at the University of Alberta decommissioned two research standpipes in 2012 that had been monitored for 30 years. These 10 m high standpipes were filled with mature fine tailings (MFT) collected from Syncrude’s Mildred Lake tailings pond. Samples were collected from Standpipe 1 prior to decommissioning to determine basic physical properties and unsaturated soil properties of the MFT. A summary of measured soil properties, including soil water characteristic curve (SWCC) and its associated shrinkage curve, are presented. The atmospheric drying of the MFT was compared using the original untreated MFT and three treated fine tailings: flocculated thickened tailings (TT) with 49% solids content, flocculated TT with 1% flyash and in-line flocculated (ILF) MFT with 32% solids content. Results show that the residual bitumen has an effect on the rate of evaporation of MFT with a low solids content. The free bitumen forms a film on the surface of the MFT, which decreases drying from deeper layers and reduces the actual evaporation. The results provide new insights into the atmospheric drying of MFT.