Proceedings Tailings and Mine Waste 2015 Vancouver, BC, October 26 to 28, 2015 Benchmarking of large-strain consolidation, sedimentation, and creep process for oil-sands tailings Krishna Chaudhary Murray Fredlund Hai Hua Lu Lianmin Xu SoilVision Systems Ltd. ABSTRACT Recent efforts in numerical modeling of the tailings consolidation processes for oil-sands tailings have raised fundamental questions related to the processes of large-strain consolidation and sedimentation. At which point does consolidation dominate? What about the sedimentation process? What about creep? The numerical modeling of the consolidation of oil-sand tailings becomes challenging if the fundamental process has not yet been established. This paper examines each of these three theories and how they relate to existing benchmarks. The performance of individual processes of large-strain consolidation, sedimentation, and the creep processes are studied. The benchmarking of single and multi-stage consolidation models is examined in light of their application the layered deposition currently proposed in industry. The performance of each theory in light of Standpipes 1 & 3 from the University of Alberta is examined in light of how each theory matches reality. The performance of each theory related to oil-sand and non-oil-sand materials is examined and reviewed. From this paper it is desired that further clarity relating to the reasonable application of each theory can be obtained for future studies and applications of the numerical methodology. Key Words: Numerical modeling, oil-sands tailings, large-strain consolidation, sedimentation, creep 1 INTRODUCTION Oil-sands mining operations in Northern Alberta produce enormous volumes of high water content tailings composed of sand, silt, clay, and a small amount of bitumen. The disposal or deposition of the tailings poses a challenge to the engineers because of its unique long-term settlement behavior. The very slow consolidation behavior of this material is believed to be caused by the extensive clay dispersion from the Clark hot water extraction process that dictates chemical interaction between clay, water, and residual bitumen and results in a significant reduction of the material’s hydraulic conductivity (Jeeravipoolvarn et al. 2009). The University of Alberta established two 10 m high, 0.9 m diameter standpipes in 1982 filled with oil-sands fine tailings in one standpipe and a mix of the fine tailings and tailings sand in the second standpipe to investigate and understand the long-term consolidation behavior of the fine tailings. The second standpipe was subsequently emptied and refilled with a new mix of material after 2 years and termed as standpipe 3 (Jeeravipoolvarn et al. 2009). In the oil-sands industry, fines are defined as <45 μm. Several researchers (Jeeravipoolvarn et al. 2008a, 2009; Pollock 1988; Suthaker 1995) have attempted to numerically predict or match the experimental data using large-strain consolidation (LSC) theory (Gibson et al. 1967, 1981; Somogyi 1980). However, the application of large- strain consolidation theory to predict the compression behavior of oil-sands fine tailings did not provide a satisfactory agreement with the experimental data (Jeeravipoolvarn et al. 2008a). This issue of disagreement leads to the question: “What is missing in the consolidation theory?” This indicates that there is either a lack of proper constitutive relationships for the problem or the correct physics of the problem is yet to be understood.