Engineers Australia

A new practical modification to the pressure plate extractor for measuring the wetting portion of SWCC

Wael M Albadri, Mohd Jamaludin Md Noor and Israa J Alhani


Soil Water Characteristics Curve (SWCC) is a graphical representation of the soil’s ability to retain water. To fully understand the soil behaviour of retaining water, a complete cycle of drying and wetting of SWCC should be measured. In common practice, SWCC measurement is limited to the drying phase only, as all the SWCC apparatuses can measure it, unlike the wetting phase which needs special attachments, modification or even certain apparatus. The pressure plate extractor in its ordinary configuration can only measure the drying phase of SWCC. This paper presents a practical modification on the pressure plate extractor (PPE) so that it is able to measure the wetting phase as well. For the purpose of verification, SWCCs from the modified apparatus and the double-walled triaxial test were measured and compared. The results from both apparatuses have shown very good agreement.