Strengths and Infinite Slope Stability of Unsaturated Soils

Shallow landslides often occur in unsaturated soil slopes under seepage conditions. The shear strength of unsaturated soils is one of the key factors in evaluating the stability of these slopes. Due to the high nonlinearity in the strength envelope of unsaturated soils, the common criteria cannot fully capture the strength characteristics of all unsaturated soils. Based on effective stress with a matric suction, a power-type strength criterion was proposed for various unsaturated soils from literature studies. In addition, performance of the power-type strength criterion was better than that of two commonly used strength criteria for modeling test data on various unsaturated soils. Furthermore, the proposed strength criterion was applied to analytically assess the factor of safety of the infinite slope under the steady seepage condition by considering the effect of grain size and porosity.