An improved volume measurement for determining soil water retention curve

The complete determination of soil water retention curve requires the sample volume to be measured, in order to calculate its void ratio and saturation degree. 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 volume displacement method. This paper proposes a simple method to avoid cracking, by limiting friction and adhesion boundary effects, to allow for an unrestrained shrinkage of the sample. Such modification of the technique decreases the error of measurements by the factor of three.