Modelling soil-structure interaction in offshore conditions with a Sanisand model.

The soil-structure interface is one of the most critical aspects in geotechnical engineering, as it concerns a thin zone at the contact between the structure and the surrounding soil where shear stresses and strains concentrate. In this study, the soil-structure interaction problem has been analysed based on the evidence of an experimental campaign carried out at the Purdue University’s geotechnical laboratory, which focused on evaluating sand-steel interface response for offshore infrastructures. A modified version of the direct shear test was used to carry out the experiments on Rohsand 3152 sand samples, considering different steel plate roughness. Two test types were conducted: the constant normal load (CNL) and the constant normal stiffness (CNS) interface tests. The aim of the thesis was to calibrate a finite-thickness interface element based on the experimentally observed results of CNL and CNS tests in order to numerically investigate the response of offshore foundation structures when in contact with coarse-grained soils. For this purpose, the advanced constitutive model Sanisand was used and implemented in a single Finite Element (FE) model using the commercial software Abaqus FEA. The comparison between the numerical model results and the experimental outcomes was judged overall satisfactory.