Determination of soil water content using time domain reflectometer (TDR) for clayey soil

Time domain reflectometer (TDR) has gained popularity among researchers in determination of soil water content due to simplicity and fast. It is a non-destructive tool to carry-out test upon soil. Rapid increment of soil water content and subsequently results in sudden reduction of soil shear strength, will cause detrimental effect to the geotechnical structure. TDR has the ability to measure soil water content on the spot without testing the moisture content of physical sample in laboratory. In this study, TDR uses two parallel probes to measure the resistance of a soil media with pre-determined volumetric water content. The results in previous study have shown that good accuracy in determination of moisture content using TDR especially for sandy and loamy soils, however in clayey soil, are yet to be confirmed. Several factors are identified to significantly affect the accuracy in measurements using clayey soils especially when the moisture content increase. The findings on determination of soil water content for Malaysian clay soil using TDR are summarized in this paper. Similar behavior were observed with past study in which the accuracy in measurement using TDR were reduced as the amount of soil water content increase of more than 30%.