Non-linear K-G Constitutive Model for Unsaturated Loess

A non-linear incremental constitutive model for unsaturated loess is proposed in this paper on the basis of Fredlund's nonlinear total constitutive law and Domaschuk-Valliappan model (K-G model) for saturated soils. The proposed model can describe the stress-strain-strength behavior and moisture change of remolded unsaturated loess. The influence of matric suction on the strength and deformation characteristics of unsaturated loess is considered in this model. Totally 14 parameters are involved in this model. When the matric suction approaches to zero, this model is degenerated to Domaschuk-Valliappan model. The method of determining all parameters is introduced in detail. The test required are (a) the isotropic compression test by controlling matric suction s constant, (b) the triaxial drained shear test by controlling cell pressure and matric suction s constant, and (c) the isotropic shrinkage test by controlling net mean stress p constant on unsaturated soils. From the test results, all parameters can be determined directly and can be utilized in the numerical calculation. The model is used to predict matric suction changes in a drained triaxial test, good agreement is obtained.