Abstract: Many landslides became unstable after the impoundment of the Three Gorges reservoir, raising awareness of the importance of research on unsaturated soil properties. The authors selected the slip-zone soil and slip-mass soil in riverside No.Ⅱ slump-mass as test objects to investigate the properties of unsaturated soil at Huangtupo landslide in Badong county. We reshaped the samples according to their natural states, and carried out tests on soil-water characteristics and tests on varying-waterhead permeability. The volumetric water content and permeability coefficient of both the soil samples under different matric suction conditions were obtained. Having fitted the soil-water characteristic test curves, we found that the fitted result by Fredlund-Xing's equation was superior to that by Gardner's equation and index attenuation equation. We also found that the characteristic curve could be influenced by the first-level suction during the test. The research result will serve as a guidance for the stability evaluation of reservoir bank during water storage.

Key words: unsaturated soil, soil-water characteristic curve, matric suction, permeability coefficient