The Impact of Capillary Trapping of Air on Satiated Hydraulic Conductivity of Sands Interpreted by X-ray Microtomography

Abstract

The relationship between entrapped air content and the corresponding hydraulic conductivity was investigated experimentally for two coarse sands. Two packed samples of 5 cm height were prepared for each sand. Air entrapment was created by repeated infiltration and drainage cycles. The value of K was determined using repetitive falling-head infiltration experiments, which were evaluated using Darcy's law. The entrapped air content was determined gravimetrically after each infiltration run. The amount and distribution of air bubbles were quantified by micro-computed X-ray tomography (CT) for selected runs. The obtained relationship between entrapped air content and satiated hydraulic conductivity agreed well with Faybishenko's (1995) formula. CT imaging revealed that entrapped air contents and bubbles sizes were increasing with the height of the sample. It was found that the size of the air bubbles and clusters increased with each experimental cycle. The relationship between initial and residual gas saturation was successfully fitted with a linear model. The combination of X-ray computed tomography and infiltration experiments has a large potential to explore the effects of entrapped air on water flow.

Keywords

residual saturation; porous media; permeability; entrapped air; two-phase flow

Published in

Water
2020, Volume: 12, number: 2, article number: 445
Publisher: MDPI

SLU Authors

• Koestel, Johannes

  • Department of Soil and Environment, Swedish University of Agricultural Sciences
    

UKÄ Subject classification

Soil Science


Publication identifier

DOI: https://doi.org/10.3390/w12020445

Permanent link to this page (URI)

https://res.slu.se/id/publ/105288