Evaluation of Capacitance Sensor for Suction Measurement in Silty Clay Loam

Measurement of soil suction is needed to develop soil-water characteristic curve, which is a mandatory input for behavioral modeling of unsaturated soil. One of the limitations of suction measuring instruments is its inability to capture wide range of suction existing in soil from near saturation to a near dry state. A recently available capacitance sensor (CS) is a promising, compact instrument for measuring wide range of soil suction, continuously, which makes it an ideal choice for several field studies. However, there are limited studies that evaluate the appropriateness of this sensor for wide range of suction measurement in different types of soils. This study critically evaluates the usefulness of CS for measuring low to high suction in a silty clay loam soil used as surface layer in a landfill cover system. This study reveals that the CS can precisely measure matric suction up to 1700 kPa for silty clay loam. Beyond 1700 kPa, the sensor measured low suction as compared to the well-established relative humidity technique. An empirical corrective procedure was proposed in this study for CS measurements greater than 1700 kPa. The corrective procedure is soil specific and depends on the reliable range of CS measurements, which need to be explored in detail.