Tensiometer saturation and the reliable measurement of soil suction

Abstract

Recent advances in the technology for measuring matric suction have permitted the direct measurement of gauge pore water pressures lower than −100 kPa—that is, absolute tensions. This significant accomplishment has opened up a realm of research possibilities into the nature and behaviour of unsaturated soils. However, the widespread exploitation of this technology has been limited by the lack of a commercially available tensiometer capable of measuring high suctions, and by the complex and highly experience-driven nature of the filter saturation process. Much of the research on the direct measurement of matric suction has focused on achieving the maximum attainable suction value with high-pressure-range devices and large saturation pressures. However, there are many applications in physical modelling and laboratory testing where smaller suction ranges are of interest (< 400 kPa), illustrating the need for more sensitive, lower-pressure-range devices. As a consequence of the lower pressure range of these devices, the devices cannot be subjected to the high saturation pressures described in the literature. As a result, additional investigations into the processes involved in filter saturation are required. This paper investigates the importance of high initial saturation, and presents conditions for quality-assured suction measurements.