Three-dimensional method for constitutive relationship of overconsolidation unsaturated soil

The generalization of constitutive model has great significance in describing the three-dimensional mechanical behaviors of soil. The Mises criterion cannot reflect the effect of Lode's angle on deformation and strength of material and the g(θ) method cannot reflect the effect of stress level on those on the π plane. To overcome these problems, an approach named transformed stress method considering the effect of Lode's angle is proposed without adding any extra parameter and can be simply applied to numerical analysis. Combining the constitutive model proposed by authors with the transformed stress method based on SMP(spatially mobilized plane), three-dimension of overconsolidated unsaturated soil is realized; continuous transition from shear yield to shear failure is achieved. Many characteristics including hardening, softening and dilatancy of overconsolidated unsaturated soil with different Lode's angles are described and compared with test data.