Installation procedure for thermal conductivity matric suction sensors and analysis of their long-term readings

Thermal conductivity matric suction sensors have enabled continuous and long-term measurement of matric suction and temperature, even in remote locations. Long-term temperature and matric suction readings were obtained from below two thin-membrane-system sites in Torquay and Bethune, Saskatchewan. The method used to install the sensors and the data acquisition system is presented. An understanding of the subgrade soil suction and temperature changes throughout the year was obtained from the data. The change in matric suction and temperature with depth and distance was also determined. Observation of the amplitude and frequency of the fluctuations in the temperature readings provided a better understanding of the changing trends. Environmental effects, such as hysteresis associated with drying and wetting of the sensors and the effect of the ambient temperature on the sensors, were found to influence the matric suction readings. Several correction factors have been proposed to eliminate the influence of the ambient temperature, and the correction methods are compared.