Field and laboratory geotechnical properties of oil sands tailings beach deposits in flume tests

William Anglow, G. Ward Wilson, Dave C. Sego, Louis K. Kabwe, Jianmin Kan

In the proceedings of: GeoRegina 2014: 67th Canadian Geotechnical Conference

Session: Laboratory and Field Testing

ABSTRACT: TOTAL E&P Canada Ltd. is performing beaching studies in test flumes using mature fine tailing (MFT) with different sand to fines ratio (SFR) at the Saskatchewan Research Council (SRC) facility in Saskatoon, SK. Results of measurements carried out on a test flume 0.25 m wide x 0.5 m height x 8.0 m length indicate that the fines content increases with increasing distance away from the discharge point (i.e., 11% fines at 2 m) to the toe of the beach slope (i.e., 15% fines at 7 m). Results also show that the hydraulic conductivity (k) measured at the same locations decreases with increasing fines content. A comparison of the in-situ data indicates that the k measured in the horizontal direction (kh) was slightly lower (~2 times) than that measured in the vertical direction (kv). A comparison of laboratory test data for undisturbed samples, however, does not show a significant difference between the measured kh and kv. Results of the soil water characteristic curve (SWCC), drying test and direct shear measurements indicate that the beach deposits are characteristics of sand/silt materials with a slight difference in texture. Results of this study are of value for the oil sands industry for the disposal, management and modelling of hydraulically deposited oil sands tailings. RÉSUMÉ TOTAL E & P Canada Ltd. effectue des tests d'épandage en canaux inclinés pour les résidus fins d'extraction (MFT) avec différents rapports sable/fines (SFR) au Saskatchewan Research Council (SRC) à Saskatoon, SK. Les résultats des mesures effectuées sur un canal de 0,25 m de large x 0,5 m de haut x 8,0 m de long indiquent que la teneur en particules fines augmente avec la distance a partir du point d'alimentation de décharge (11% fines à 2 m) jusqu'au point de décharge du canal (15% fines à 7 m). Les résultats montrent également que la conductivité hydraulique (k), mesurée aux mêmes emplacements diminue avec l'augmentation de la teneur en particules fines. Une comparaison entre les données in-situ indique que k mesurée horizontalement (kh) est légèrement 2 fois inférieure à celle mesurée verticalement (kv). Cependant, une comparaison des données de laboratoire pour les échantillons non perturbés ne montre pas de différence significative entre kh et kv. Les résultats de la courbe caractéristique de l'eau du sol (SWCC), des essais de séchage et de cisaillement direct indiquent que les dépôts d'épandage ont les caractéristiques similaires des matériaux sable/limon avec une légère différence dans leur texture. Les résultats de cette étude sont de valeur pour l'industrie des sables bitumineux pour l'entreposage, la gestion et la modélisation des résidus de sables bitumineux déchargés hydrauliquement. 1 INTRODUCTION The disposal and reclamation of oil sands tailings have emerged in recent years as primary concerns governing the operations in the oil sands industry. Traditional disposal methods involved the discharge of total tailings in ponds and impoundments. Upon tailings deposition, the solids in the tailings stream segregate with the sand forming dykes and beaches, and about one-half of the fines and most of the water flowing into a tailings pond. Upon settling for two years these fluid fine tailings (FFT) reach a solids content of around 30% and are then termed mature fine tailings (MFT). The tailings are predominately medium-fine sand, but contain from 5% to 40% fine silt and clay and bitumen by mass. Concern about the growing volume of MFT resulted in the Energy Resources and Conservation Board (now Alberta Energy Regulator, AER) establishing new requirements for oil sands fine tailings (ERCB 2009). The objective was to reduce the amount of fluid tailings being produced by requiring 50% fines capture in dedicated disposal areas (DDAs). In light of this directive, the oil sands industry has been intensively researching possible improvements to tailings management practices, including the use of non-segregating composite and thickened tailings (TT) discharge (Matthews et al. 2002, Chalaturnyk et al. 2002) as well as heavy mineral recovery techniques from the tailings streams (Ciu et al. 2003). However, tailings are still mainly deposited as slurries, and the understanding of the depositional behaviour of the tailings slurry is of critical importance. Furthermore, the stability of the tailings beach formed upon deposition affects the integrity of the impoundment as a whole due to the susceptibility of the tailings sand to both static and cyclic liquefaction failures (Lade 1992, Pastor et al. 2002). Tailings beach studies have therefore become an integral part of the design and sustainable operation of tailings disposal sites. Blight et al. (1985) showed that field conditions prevailing in the tailings beach could be adequately modelled to a smaller laboratory scale with the use of flume tests. The authors further highlighted the influence of the fines captured by the beach and their migration

RÉSUMÉ: eld and laboratory geotechnical properties of oil sands tailings beach deposits in flume tests

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William Anglow; G. Ward Wilson; Dave C. Sego; Louis K. Kabwe; Jianmin Kan (2014) Field and laboratory geotechnical properties of oil sands tailings beach deposits in flume tests in GEO2014. Ottawa, Ontario: Canadian Geotechnical Society.

@article{GeoRegina14Paper305,author = William Anglow; G. Ward Wilson; Dave C. Sego; Louis K. Kabwe; Jianmin Kan,title = Field and laboratory geotechnical properties of oil sands tailings beach deposits in flume tests,year = 2014}