Volume 33, Issue 5 (September 2010)
Principle and Prototype Testing of a New Matric Suction Sensor
A new principle for matric suction measurement is proposed, based upon strain measurement of a contiguous porous material of high air-entry value (AEV). In theory, this allows for the measurement of matric suction without the associated errors due to cavitation or hysteresis for suctions below the AEV. Results from testing a prototype sensor made from a deformable porous material with a high AEV (S=0.85 at 5 MPa) are presented. Deformation of the prototype was determined by means of attached electrical resistivity strain gauges. Matric suction is then inferred from the strain measurements using poroelasticity theory. Tests performed in a drying artificial silt show that matric suction values inferred using the prototype sensor showed reasonable agreement with corresponding values obtained using a tensiometer, a psychrometer, and with suctions established using axis-translation. Mean absolute errors of matric suction measurement were 8, 16, and 100 kPa for ranges of 0–150, 50–300, and 300–1200 kPa, respectively.