Combining two methods for the measurement of hydraulic conductivity over a wide suction range

Abstract

The hydraulic conductivity of unsaturated soils can span several orders of magnitude. The measurement of hydraulic conductivity over a wide suction range is a challenging task for decades. In this study, numerical tests are carried out to check the assumption, error sources, and applicable conditions of the wetting front advancing method and instantaneous profile method. Based on the numerical test results, a digital wetting front advancing method is proposed to measure hydraulic conductivity of unsaturated soils in the relative high suction range and the traditional instantaneous profile method is found to be robust in measuring hydraulic conductivity in the low suction range, e.g. for soil with a degree of saturation above 0.9. Further, a combination of the digital wetting front advancing method and the traditional instantaneous profile method is implemented in the same soil column test and leads to an accurate soil hydraulic conductivity function over a wide suction range. The proposed method is applicable to various soil types and the test duration is only 1 ~ 5 days, thus makes the measurement of hydraulic conductivity a routine experiment for unsaturated soil mechanics.