Cavitation in high-capacity tensiometers: effect of water reservoir surface roughness

High-capacity tensiometers (HCTs) are sensors made to measure negative pore water pressure (suction) directly. In
this paper, a new approach is proposed to expand the range and duration of suction measurements for a newly
designed HCT. A new technique is employed to reduce significantly the roughness of the diaphragm’s surface on the
water reservoir side in order to minimise the possibility of gas nuclei development and the subsequent early
cavitation at the water–diaphragm interface. The procedures employed for the design, fabrication, saturation and
calibration of the new tensiometers are explained in detail. Furthermore, the performance of the developed HCTs is
examined based on a series of experiments carried out on a number of unsaturated clay specimens. An improvement
in maximum sustainable suction in the range of 120–150% of their nominal capacity was obtained from different
surface treatment methods. Moreover, the results show an improvement of up to 177% for the long-term stability
of measurements, compared to the developed ordinary HCTs with untreated diaphragms.