Field suction measurements are especially important for pavements constructed on unsaturated expansive soils. Since subgrades supporting pavements can experience high suctions during dry seasons, field sensors that can measure high suctions in subsoils are necessary. In this research, thermal conductivity based soil suction sensor was evaluated for matric suction measurements at several sites. Filter paper method was used in the laboratory suction measurements and these results are used for comparison with the field suction measurements with the sensors. Soil water characteristic curves derived from both laboratory and field measurements showed close agreements. Volume change measurements using swell and shrinkage tests were separately conducted on the subgrade soils retrieved from the instrumented test sites. With the sensors used, the laboratory and field monitored suction data showed the need for an adjustment or shift of the time factor to obtain accurate values of high suctions. The influence of total suction on the volumetric swell and shrinkage characteristics of the soils were addressed.
Samenvatting