Evaluation of candidate polymers to maximize geotechnical performance of oil sands tailings

Abstract

Oil sands fluid fine tailings deposits are challenging to reclaim due to their inherently high natural water content, low permeability, and low strength. Combinations of polymers and/or coagulants are used by operators to improve the dewatering and strength properties of the tailings. However, considerably more work has been done to evaluate polymer performance with short-term dewatering metrics rather than with long-term metrics such as consolidation properties. This paper evaluates the potential of four novel polymers for use in fluid fine tailings treatment compared to a commercially available polymer and untreated tailings specimen. The performance of the polymers was assessed through initial screening with respect to short-term dewatering, evaluation of the consolidation and strength properties using large strain consolidation tests, shear sensitivity in pipeline transport, and finally, large strain consolidation modelling to appraise the relative potential performance under different strategies, such as terrestrial or aquatic reclamation options. One polymer exhibits remarkably fast dewatering at high void ratios, while another demonstrates dense and shear-resistant flocs. The paper discusses each polymer's distinctive tailings fabrics and how their unique merits and limitations would benefit different reclamation eventualities. Finally, potential improvements of the polymers are suggested for future assessment.

Consolidation and unsaturated properties of in-line flocculated fluid fine tailings and centrifuged tailings from oil sands mines

“…The important conclusion is that the C-Cake will consolidate much faster at lower void ratios than 1.6. The speed of consolidation is the benefit of centrifugation (Wilson et al 2018;Abdulnabi et al 2021).…”

“…The properties of the ILF-FFT and C-Cake samples, tested by LSC, are compared with those using the Tempe cell technique to assess the effects of the treatments. The LSC technique is tedious and time-consuming and takes several months to one year to complete an oil sands tailings test (Amoako et al 2020;Abdulnabi et al 2021). Such lengthy laboratory tests affect practical engineering design as rigorous timelines drive the engineering industry.…”

Large strain shearing behaviour of untreated and polymer treated clayey silt slurry specimens

“…Owing to the increased application of forms of PT, studies to characterise the effects PT may have on post-deposition geotechnical behaviour of the treated slurry have been undertaken. Broadly, these studies have indicated the following effects of PT: lower consolidated densities at a given vertical effective stress and higher permeability at a given density (Jeeravipoolvarn et al 2009;Yao 2012;Manzotti et al 2014;Beveridge et al 2015;Gholami & Simms 2015;Reid & Boshoff 2015;Riley et al 2015;Znidarcic et al 2015;Reid & Fourie 2016, 2018aAbdulnabi et al 2022), higher undrained shear strengths at a given density (Jeeravipoolvarn et al 2009;Yao 2012;Beier et al 2013;Manzotti et al 2014;Cooling & Beveridge 2015;Gholami & Simms 2015;Reid & Fourie 2016Abdulnabi et al 2022) and higher CSL elevation (Reid & Fourie 2016), and various contrasting outcomes when examining the effects of PT on brittleness in undrained monotonic or post-cyclic shearing (Beier et al 2013;Gholami & Simms 2015;Reid & Fourie 2017) and drastically different penetrometer responses (Reid and Fourie 2018a), with a summary of recent studies provided by Reid and Fourie (2018b).…”

“…The effect of PT on the normal consolidation line (NCL)/critical state line (CSL) elevation and undrained strength at a given density has potentially important applications given the prevalence of methods based on the CSL to characterise the state and liquefaction susceptibility of tailings (Robertson et al 2000(Robertson et al , 2019Jefferies & Been 2015;Morgenstern et al 2016;Jefferies et al 2019;Arroyo & Gens 2021;Reid et al 2021). While the CSL measured in the work of Reid and Fourie (2016) adopted the conventional approach of defining the CSL using triaxial compression tests, a question that follows is whether, at shear strains higher than can be applied in the triaxial test (e.g.…”

Large-Strain Consolidation Analysis Accounting for Time-Dependent Effects in Clayey Tailings and Soft Soils

“…An accurate large-strain consolidation (LSC) analysis plays a critical role in the management of deposits of soft geomaterials, as such an analysis is required to estimate depth profiles of density, strength, and rate of settlement, all of which are important for the management of tailings (Carrier 1983;Abdulnabi et al 2022) and other soft sediments (Schiffman 1982). The current standard of practice for consolidation analysis, specifically for tailings, especially clayey tailings, is to employ analytical or numerical solutions based on Gibson's one-dimensional (1D) finite strain consolidation theory for saturated clays .…”