Filter paper method for suction measurement using electrical resistivity

The filter paper method is an economical, easily accessible, and simple-to-use method to measure total or matric suction over a wide suction range. Difficulty in handling the filter paper can result in inaccurate water content determination of the filter paper leading to poor estimation of the suction. This paper examines the feasibility of using electrical resistivity of the filter paper in the non-contact mode to determine equilibrium time and to infer the total suction. It was shown that for a specific set-up, electrical resistance (ER) can be used in place of electrical resistivity. Relationships between ER and water content of the filter paper and between ER and total suction were first established. Finally, a prototype set-up is used to demonstrate how it can be used to measure the total suction of soil specimens. It was demonstrated that ER of the filter paper can be used to provide a reasonable estimate of total suction greater than 100 kPa with an error between-18 and +10%. Better accuracy can be achieved if each filter paper is calibrated before use.