Soil suction measurement using the Xeritron Sensor in two different types of infiltration tests on a swelling soil

摘要

A new suction sensor has been developed that can measure the entire range of suction. It works on the basis of vapour equilibrium and measures relative humidity, from which total suction can be directly calculated. The sensor is a Xeritron XN1018 relative humidity sensor from Hygrometrix. The Xeritron Sensor was chosen because of its wide range of measurement, accuracy, small size and durability. The sensor measures relative humidity from 0-100%. It is enclosed in a stainless steel casing and has electronic connections embedded in strong epoxy. The Xeritron Sensor was modified so that it could be compacted inside triaxial specimens. The modified sensor is just 7.7mm in diameter and 37.5mm long. Calibration results are shown to display the Xeritron Sensor's wide measurement range. Finally, a suction comparison is presented from two types of infiltration tests performed in the triaxial cell. Boundary conditions applied during the two infiltration tests are constant pressure and constant volume. Results show a distinctive suction response during infiltration tests due to boundary conditions. Suction decrease occurs at a faster rate during constant pressure tests compared to constant volume tests. However, during the constant volume test, suction equilibrates to a lower value compared to the constant pressure boundary condition.