Assessing compressibility and hydraulic conductivity relationships of oil sands tailings derived from a combined constant-pressure filtration and incremental cake compression test

A filtration-consolidation (F-C) technique is proposed to determine the non-linear consolidation constitutive relationships for compressibility (e – σ') and void ratio-hydraulic conductivity (k – e). A single constant filtration pressure was applied to three different oil sand tailings slurries, including two samples of fluid fine tailings (FFT) known for their high plasticity, and a mixture of FFT and sand tailings classified as a material with low plasticity. This was done using OFITE’s Multi-Unit filter press to observe the pressure-dependent behavior of the average specific cake resistance. Incremental compression pressure was also used to determine equilibrium cake porosities at different filtration pressure levels. Filtrate flux measurements and calculated equilibrium cake porosities were used with an iterative non-linear curve fitting algorithm to determine empirical parameters of constitutive equations. Comparison with multi-step large strain consolidation (MLSC) tests shows F-C test compressibility data closely matching MLSC test data within the F-C pressure range. Nevertheless, the hydraulic conductivity trend observed in the F-C test resembled that of the MLSC test, albeit being one order of magnitude lower. Overall, the F-C test offers a rapid method to assess the filterability of oil sands tailings and to derive the large strain consolidation behavior of the tested samples.