Volume 34, Issue 5 (September 2011)
Characterization of Transparent Soil for Unsaturated Applications
Experimental characterization of unsaturated soils is of primary importance to further understanding of fundamental behavior, as well as allow for accurate modeling and predictions, of constitutive and field behavior. In the laboratory, the most common research methodology used to investigate the hydraulic behavior of unsaturated soils involves placing the unsaturated soil in a column apparatus with measurements of pore pressure and moisture content being made at discrete locations distributed along the elevation of column. These types of tests have provided many valuable insights into unsaturated flow phenomena; however, there are some limitations with this methodology including the discrete nature of the measurement points. In this paper, an alternative method is proposed which aims to combine the use of digital image analysis with a transparent soil to avoid the ambiguity of traditional boundary image measurements of moisture content in column experiments. At 100% saturation, the transparent soil particles appear invisible and allows for the ability to see through the soil mass. Any air bubbles will be visible within the soil voids and as a result, at varying degrees of saturation less than 100%, the soil will become progressively non-transparent. The relationship between pixel intensity of the unsaturated soil and degree of saturation is defined and validated. This relationship allows definition of the degree of saturation throughout the column profile thus giving the opportunity to verify and further develop constitutive models for unsaturated hydraulic behavior.