Strength Model of Unsaturated Clays with Adsorptive Effects

The interactions between liquid phase and solid matrix in unsaturated clays can be divided into capillary effects and physicochemical effects according to their formation mechanism. The physicochemical effects (that is, the adsorption effects) become significant at low saturation degrees. However, current strength models for unsaturated soils almost are established on the basis of capillary mechanism, and the contribution of adsorption effects to soil strength is neglected. A binary-medium shear strength model is firstly proposed, involving the capillary and adsorption effects. The unsaturated clay is assumed to consist of two ideal parts, i.e., the ideal capillarity part and the ideal adsorption part, and then the corresponding ideal strength formulas are established. Furthermore, a participation function is used to reflect the degrees of capillary effects and adsorption effects. Finally, predictions are performed on the shear strength of unsaturated clays. After comparing predicted results and exiting test results, it is shown that the proposed model can well describe the strength of unsaturated clays.