Structural bonding-breakage constitutive model for natural unsaturated clayey soils

The natural clayey soils are usually structural and unsaturated, which makes their mechanical properties quite different from the remolded saturated soils. A structural constitutive model is proposed to simulate the bonding-breakage micro-mechanism. In this model, the unsaturated soil element is divided into a cementation element and a friction element according to the binary medium theory, and the stress-strain coordination for these two elements is obtained. The cementation element is regarded as elastic, whereas the friction element is regarded as elastoplastic which can be described with the Gallipoli’s model. The theoretical formulation is verified with the comparative experiments of isotropic compressions on the saturated and unsaturated structural soils. Parametric analyses of the effects of damage variables on the model predictions are further carried out, which show that breakage deformation of natural clayey soils increases with the rising amount of initial defects.