Abstract: The traditional methods for determining the soil-water characteristic curve (SWCC) in the full suction range always takes several months. To better guide the engineering practice with the theory of unsaturated soil mechanics, the rapid determination of SWCC is particularly important. In this study, a rapid measurement method for SWCC in the wide (full) suction range was developed with the combination of pressure plate method, parallel filter paper method and dew point potentiameter method, and the proposed method was used to test two different soils. Results showed that: i) The experimental data of the parallel filter paper method and that of the serial filter paper method were in good agreement, so the parallel filter paper method can be used instead of the serial filter paper method to shorten the measurement time. ii) When the measured data meet the general shape of SWCC (or meet the requirements of engineering design), the number of tests can be reduced appropriately to improve the measurement efficiency. A complete SWCC can be determined by the proposed combined method with only 10 to 12 points. iii) The measurement method proposed in this study can shorten the measurement time of SWCC testing from several months to 7–10 days. The combined method proposed in this study achieved the rapid and accurate determination of SWCC in wide (full) suction ranges, which is expected to make the SWCC measurement become a routine geotechnical test.

Key words: rapid determination, soil–water characteristic curve, pressure plate method, parallel filter paper method, dew point potentiameter