Abstract: The hydraulic conductivity function of unsaturated soil spans several orders of magnitude. Traditional measurement methods often take several months, and it is difficult to measure the hydraulic conductivity in the full suction range. In order to realize the rapid measurement of hydraulic conductivity in the full suction range, the wetting front advancing method is combined with the instantaneous profile method (here referred to as the combined determination method) in this study. A self-developed soil column infiltration device was used to measure the hydraulic conductivity of Qinghai silty clay in the full suction range under different dry densities. The test results show that in the combined determination method, the wetting front advancing method is suitable for the measurement of hydraulic conductivity in the high suction range ( > 25 kPa), while the instantaneous profile method is suitable for measuring the hydraulic conductivity in the low suction range ( ≤25 kPa). The hydraulic conductivity determined by the two methods in the overlapped suction range is basically consistent. The combined determination method can reduce the measurement time of hydraulic conductivity in the full suction range by about one week with good accuracy. In addition, the error sources of the two measurement methods are also analyzed and discussed in this work. The results show that the combined determination method can realize the rapid measurement of hydraulic conductivity in the full suction range, which is expected to make the measurement of the hydraulic conductivity of unsaturated soil become a routine test in soil mechanics.

Key words: full suction range, rapid determination, hydraulic conductivity, wetting front advancing method, instantaneous profile method