Abstract
In this paper, several theoretical aspects for preparation of constitutive equations of unsaturated soils are discussed. First, possible pore water states are described. Three states, insular air, fuzzy and pendular saturation are taken into account to examine the mechanical behavior of unsaturated soils. Suction effects are clarified for each state and these are used to interpret the overall mechanical behavior of unsaturated soils. The suction effects can be classified into two categories. One is that an increase in suction induces an increase in effective stresses and the other is that an increase in suction induces an increase in both yield stress and the stiffness of the soil skeleton against plastic deformations. The first suction effect can be estimated by formulating the relationship between suction and shear strength at the wet side of critical state . The second suction effect can be estimated from the state surface concept. The modified Cam clay model with these suction effects is proposed. The performance of this model will be examined in the paper (Kohgo et al., 1993).
