Performances of Two High Capacity Tensiometers

Abstract

Two High Capacity Tensiometers (HCT) have been developed at the University of Napoli Federico II (UNINA) using a design layout similar to that of Ridley and Burland (1993). One of the HCT includes a O-ring sealing and a high air-entry value disk (HAEV) to protect a water-saturated measurement chamber from desaturation. The second one eliminates the O-ring in the attempt to enhance the time-response and improve the mechanical design for the calibration in the “negative” pressure range. Two different pre-conditioning devices have been developed to water-saturate the HAEV and the measurement chamber. The HCT may also be calibrated in the same chamber by applying positive values of water pressure to the first prototype, and positive value of air pressure, to the second prototype, for ‘negative’ calibration. A number of free evaporation tests and matric suction measurements against preconditioned soil samples are presented in the paper and discussed in order to highlight the performances of the two HCTs.