In situ matric suction and moisture content measurements in expansive clay during seasonal fluctuations

In the design of flexible pavements using the mechanistic-empirical pavement design guide (MEPDG), water flow analyses are used to predict changes in the mechanical behavior of unsaturated subgrade soils. However, the water flow analyses in the MEPDG are not well validated using field measurements of moisture content and matric suction with time. A research study was initiated to measure the variation in matric suction and moisture content in an expansive soil during seasonal fluctuations. Specifically, a thermal conductivity-based suction sensor was fully evaluated and calibrated in the laboratory and was later installed with moisture sensors at different sites in Texas. This paper presents a summary of field measurements of matric suctions and moisture contents from a site in Houston. Comparisons of field measurements of matric suctions are compared with those interpreted from the soil water characteristic curve using field moisture content measurements, and a decent match was obtained up to matric suctions close to 800 kPa.