A Comparison of Total Suction Measurements with Thermocouple Psychrometer, Filter Paper Technique, and Chilled-Mirror Device

Soil suction is one of the most important parameters describing the moisture stress condition of unsaturated soils, and its measurement is equally important for realistic applications of unsaturated soil mechanics. The thermocouple psychrometers, filter paper method and chilled-mirror device are three soil suction measurement techniques that have found their places in describing the behavior of unsaturated soils in geotechnical engineering practice. However, as it is inherent with all the suction measurement methods there are still difficulties and uncertainties associated with these soil suction measurement techniques. In this paper, the filter paper, chilled-mirror psychrometer, and thermocouple psychrometer methods are evaluated and compared based on some recent observations and test results. These methods are used to measure total suctions of some high plasticity clay soils under very strict temperature control conditions. From the test results, the capabilities and limitations of the three methods are analyzed.