Slope stability of expansive soil under fissure influence

Expansive soil is a kind of fissured soil. The slope stability of the expansive soil is strongly influenced by fissures. The fissures cause remarkable decrease of the soil strength. The uniform layer of the expansive soil is divided into layers with different strength properties due to depth of the fissures. Rain water in the fissures forms seepage, which increases the sliding moment of the slope. The fissures develop with time. All these factors obviously influence the slope stability. A method for slope stability of the expansive soil based on the conventional slice method is developed. The slope of the expansive soil is divided into 3 sub-layers, the layer with fully developed fissures, the layer with partially developed fissures, and the layer with- out fissures. The approximate determination methods for fissure depth, surface of sub-layers and phreatic line of seepage in fissures are given. The proposed method reflects the mechanism of slope failure of the expansive soil and can simulate many characteristics of slope failure of the expansive soil, such as that the sliding mass body is shallow, gentle and drawing-shaped, and that the sliding happens seasonally, directionally and after long time. The computed results of an example show that the developed method is reasonable and practical.