Visco-Hypoplastic Model for Structured Soils

The Visco-hypoplastic constitutive model is developed for fine-grained soils and reproduces the viscous behavior of these materials such as creep, relaxation and rate dependence. The model adjusts to the Butterfield's compression law at isotropic states. Nevertheless, it is not able to simulate the influence of the structure in the materials mechanical behavior and hence, an extension has been proposed herein. This extension introduces a new state variable representing the material structure defined as the ratio of the preconsolidated mean stress at intact and remolded states for the same material. The structure follows a degradation law which accelerates after yielding and decreases until the remolded state is reached. The overconsolidation ratio OCR and the material stiffness increase along with the structure values. The structure influence in the stiffness is reproduced by modifying the Butterfield's compression law at the elastic range. Simulations on a high structured soil show satisfactory results, and a numerical implementation for FEM has been developed.