Permeability function for oil sands tailings undergoing volume change during drying

Feixia Zhang,D.G Fredlund,G Ward Wilson

doi:10.1139/cgj-2016-0486

Abstract

The coefficient of permeability function is an important unsaturated soil property required when modeling seepage and contaminant transport phenomena. Inaccuracies in the estimation of the permeability function can lead to significant errors in numerical modeling results. Changes in void ratio and degree of saturation are factors that influence the permeability function. Presently available methodologies for estimating the unsaturated permeability function make the assumption that there is no volume change as soil suction is changed. As a result, volume changes are interpreted as changes in degree of saturation. The commonly used estimation techniques for the permeability function are reasonable for soils such as sands that experience little volume change as soil suction is changed. On the other hand, inaccurate results are generated when soils undergo volume change as is the case with oil sands tailings. Revisions to previous methodologies are proposed to render the estimation of the permeability function more suitable for simulating the drying process associated with soils that undergo high volume changes. The revised methodology independently analyzes the effect of volume changes (i.e., changes in void ratio) and degree of saturation changes (i.e., changes in S-SWCC (degree of saturation - soil-water characteristic curve)). Laboratory data on thickened oil sands tailings are presented and interpreted within the context of the proposed methodology.

Highlights

Background on SWCC, shrinkage curve and permeability functions Literature review on the role of the SWCC The SWCC describes the relationship between the amount of water in the soil and its corresponding soil suction, and the drying relationship differs from the wetting relationship (Tami et al 2004)
The influence of a change in the degree of saturation is presented as a relative permeability function
The quality of the fit of the S-SWCC affects the quality of the estimated permeability function

Summary

Introduction

Background onSWCC, shrinkage curve and permeability functions Literature review on the role of the SWCC The SWCC describes the relationship between the amount of water in the soil and its corresponding soil suction, and the drying relationship differs from the wetting relationship (Tami et al 2004). The shrinkage curve equation proposed by Fredlund (2000) is used in this study as the basis for separating the effects of volume change and degree of saturation effects when estimating the permeability function for high volume change soils.

Results

Conclusion