Small Strain Soil Constitutive Models HS-SMALL & RU+MCC – Calibration and Verification

The paper presents two reasonably advanced constitutive laws for soil. First one is a hybrid of the Modified Cam Clay and a new RU (reload, unload) development, and it is author's conception. The second one is a HS-small model by Benz. In the RU+MCC model, the Modified Cam Clay model, which is an isotropic elastoplastic hardening, describes normal consolidation behaviour - plastic model originated by Burland in 1967 within the critical state soil mechanics. This model describes realistically mechanical soil behaviour in normal consolidation states. The RU part is designed to ensure more adequate soil responses to reloading paths, particularly in the range of small strains. The HS-small model is an improvement of HS model originated form Schanz and Vermeer. This concept base on cap yield surface with incorporation of two hardening mechanisms, stiffness variation at small strains, densification mechanism, Rowe's dilatancy and some others. The author in the FEM computer code Z_SOIL.pc has implemented the RU + MCC model. The HS-small model has been implemented into the same software by Truty. To test the influence of the small strain nonlinearity on soil - structure interaction as well as to exhibit the ability of the proposed model to simulate realistically this effect, a comparative study based on the FEM solution has been carried out. As a benchmark, a trial loading test of strip footing was used. The calibration process has based on advanced laboratory and field soil tests like resonant columns, triaxial test, dilatometer test and many others. (paper)