Abstract: In order to study the influence of water content on the strength and deformation of slip soil, select a large scale landslide’s slip soil is selected to conduct consolidated-drained triaxial shear test with different initial saturations. Study the volume strain of unsaturated soils is studied by adopting a new gas and water converting device. The results show that the water content has great influences on the strength of slip soil; the higher the initial saturation is, the lower the strength value is. Strength parameter c with saturation is the ladder-like drop relationship; and linear relation could be established between strength parameters ? and initial saturation. The higher water content is, the smaller the soil sample’s volume deformation is; and the parameters of Duncan-Chang model such as K, Kb, and G are affected largely by water content; and then the linear formula could be established between the initial saturation and these parameters of Duncan-Chang model. But other parameters of Duncan-Chang model such as n, m, F, Rf, and D, which are little affected by water content, have little difference value under different initial saturations, so the averages are made as the model parameters under different saturations.

Key words: slip soil, water content, external volume strain, strength, deformation