Abstract: This paper presents some recent advances in the stability analysis of expansive soil slopes by the Changjiang/Yangtze River Scientific Research Institute. Types and distributions of fractures were investigated through researches on the expansive soils in the middle route of the South-to-North Water Diversion Project. It was revealed that differences existed between the fractures of expansive soils of the upper and the lower portions of “ the depth of atmosphere influence ” . The initial fractures in the lower portion were found to be obviously directional. By dilatancy analysis for the expansive soils with the same initial water content and water absorption, high linear relationship was obtained between the swelling strain and the mean stress in the semi  logarithmic coordinate. The determination of strength and new test method of expansive soils were provided considering heterogeneous anisotropic and nonlinear properties of the strength of expansive soils. The failure mechanism of expansion soils slopes was analyzed, and the deformation modes were also given. The overall stability of expansive soil slopes not only depended on gravity, but was also controlled by the strength of fracture planes ； while the destabilization of the shallow soil body was mainly subject to the expansive deformation under moistening. Stability analysis methods were employed for expansion soli slopes with two deformation modes, and the results indicated that the slope stability could be precisely reflected by stability analysis achievements using strength test values.

Key words: South-to-North Water Diversion Project ,  expansive soil  ,   slope  ,   stability  ,   fractures  ,  computed tomography  ,   deformation mode  ,   stability analysis method