Abstract: This paper studies the strength characteristics of the Hengyang unsaturated granitic residual soils. The soil water characteristic curves of the granitic residual soils were determined by the filter paper method and the consolidated undrained shear tests were performed to analyze the influence of the initial matrix suction and the water content on the strength of the soil. The results indicate that, within the range of tested moisture, the suction of the unsaturated granitic residual soil decreases with the increase of the moisture content, but the moisture content is less affected by the initial matrix suction. Correspondingly, the internal friction angle decreases linearly with the increase of the moisture content and the cohesion changes in a quadratic relationship. The change of the initial matrix suction in relation with the internal friction angle and cohesive is nonlinear.

Key words: Unsaturated Residual Soils, Moisture Content, Matric Suction, Shear Strength