An improved volume measurement for determining soil water retention curves

The complete determination of soil water retention curves requires the sample volume to be measured in order to calculate its void ratio and degree of saturation. During drying in the pressure plate apparatus, cracks often appear in the sample altering its deformation and evaporation patterns. Consequently, this causes a significant scatter in the volume measurement when using the volume displacement method. This paper proposes a simple method to avoid cracking, by limiting friction and adhesion boundary effects, to allow for unrestrained shrinkage of the sample. Such modification of the technique decreases the measurement error by a factor of three. Copyright © 2007 by ASTM International.