Pore Size Distributions of Soils From Mercury Intrusion Porosimeter Data

Abstract Soil water characteristic curves are routinely determined by the pressure plate and pressure membrane techniques. Similar curves can be derived from pore size distribution curves obtained by the mercury intrusion porosimeter technique. Mercury is forced under pressure into previously oven‐dried and evacuated samples. The applied pressure is increased in discrete steps and the volume of pores intruded between pressure steps is obtained. Equivalent pore sizes corresponding to the applied pressures are calculated with the pressure of displacement equation. This technique allows analysis of many samples per day and has therefore an advantage over standard methods. Soil water characteristic curves of eight soils ranging in clay content from 0 to 57% were determined by the pressure plate and pressure membrane technique and compared with similar curves derived from mercury intrusion data. Results obtained by the two techniques agreed well for soils which do not shrink or swell with changes in water content, but not for samples with swelling clays.