Assessment of Liquid Saturations in Sand by Image Analysis Suwasan Sudsaeng 1,a , Siam Yimsiri 2,b , and Suched Likitlersuang 1,c 1 Department of Civil Engineering, Chulalongkorn University, Bangkok, Thailand 2 Department of Civil Engineering, Burapha University, Chonburi, Thailand a suwasans@gmail.com, b ysiam@buu.ac.th, c fceslk@eng.chula.ac.th Keywords: optical density, liquid saturation, image analysis, immiscible fluid, unsaturated sand Abstract. This research investigates the relationship between optical density and liquid saturations in unsaturated sand using multispectral image analysis technique. The tested liquids are water, diesel, and parafin liquid. The experiments are performed on two-fluid phase systems (water-air, diesel-air, and parafin liquid-air) and three-fluid phase systems (diesel-water-air and parafin liquid-water-air). Water is dyed with Brilliant Blue FCF, whereas diesel and parafin liquid are dyed with Red Sudan III. Using consumer-grade digital cameras, two images of sand specimens with various liquid saturations are taken with two different band-pass filters. The analysis results show that, for the sand and investigated fluids, the optical density defined for the reflected luminous intensity is a linear function of the degrees of fluid saturation for each spectral band and for any two- and three-fluid phase systems. Introduction Subsurface and groundwater contamination with organic products is a serious health and environmental problem in many parts of the world. These organic products are often associated with halogenated compounds used as industrial solvents or petroleum hydrocarbons, which can be classified as a light non-aqueous phase liquid (LNAPL) because of its lower density than water. When released into the ground, it can persist in the environment due to its negligible solubility in water. To remediate LNAPL-contaminated sites in an efficient manner, a complete understanding of contaminant infiltration behavior is essential. This understanding should be based on an accurate numerical model which has been validated against quantitative laboratory experiments. However, there have been few multiphase flow experiments where dynamic monitoring of pressure and saturation distributions of NAPL, water, and air are presented. Generally, the non-destructive methods used to measure fluid saturations [e.g. 1, 2, 3, 4] do not allow the acquisition of dynamic fluid saturation distribution in the entire flow domain at one time. Therefore, this study investigates the application of the multispectral image analysis method [5] to obtain the relationship between an average optical density and degrees of liquid saturation in sand. Multispectral Image Analysis Method (MIAM) The Multispectral Image Analysis Method (MIAM) [5] is an alternative tool to measure dynamic LNAPL, water, and air saturation distributions in 2-D three-fluid phase laboratory experiments. This technique provides a non-destructive and non-intrusive tool for multifluid flow imaging of systems with rapid change. It provides the relationship between an Average Optical Density (AOD) and degrees of liquid saturation in sand. The optical density (D r ) is defined in terms of reflectance as shown in Eq. (1).         − = 0 log I I D r r (1) where I r and I 0 are intensities of reflected light and light that would be reflected by an ideal white surface, respectively. Applied Mechanics and Materials Vols. 256-259 (2013) pp 494-498 © (2013) Trans Tech Publications, Switzerland doi:10.4028/www.scientific.net/AMM.256-259.494 All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of TTP, www.ttp.net. (ID: 202.28.78.12-06/11/12,09:26:05)