Use of thermal conductivity sensors to measure matric suction in the laboratory

Abstract

The measurement of soil suction is pivotal to the application of soil mechanics principles in geotechnical engineering practice related to unsaturated soils. Volume change, shear strength, and seepage analyses all require an understanding of the matric suction in the soil. This note summarizes the use of thermal conductivity sensors to measure matric suction in the laboratory. The thermal conductivity sensor is described along with its mode of operation. A brief description is given of the procedure for calibrating thermal conductivity sensors using a pressure plate apparatus. The measurement of matric suction can be performed in the laboratory on Shelby tube samples. The laboratory measurements of matric suction can be adjusted for the effect of overburden pressure in the field. The required equilibration time for suction measurements is discussed along with details of the test procedure. The applications of the measured suction values to design are briefly discussed.Key words: matric suction, negative pore-water pressure, thermal conductivity sensor, laboratory, undisturbed samples.