Effect of Initial Conditions on the Interpretation of Soil-Water Characteristic Curves (SWCCs) in Geotechnical Engineering

The test procedure for measuring the soil-water characteristic curve, SWCC, have been largely established within the soil physics discipline over a period of several decades. More recently, these test procedures have been incorporated into geotechnical engineering practice. While there are benefits associated with utilizing past experience, further refinement of the analytical procedures used in soil physics are required when estimating unsaturated soil property functions. The primary assumption that has historically been made is that insignificant volume change occurs as soil suction is increased during the drying process. This assumption may be satisfactory for certain soil types and conditions, but in general, the effects of volume change are significant for many soils and must be taken into consideration when estimating USPFs. The shrinkage curve (SC) of a soil can be effectively used to take volume changes upon drying into consideration. The shrinkage curve can readily be measured but there are also a number of means whereby the curve can be estimated with sufficient accuracy. This paper outlines the steps involved in independently assessing the effects of volume change and desaturation on the calculation of unsaturated soil property functions. The shrinkage curve is used to separate the various volume-mass SWCCs required when dealing with various unsaturated soil mechanics problems. The proposed analytical procedure is described for estimation of hydraulic properties for low to high compressibility soils.