On consistent nonlinear analysis of soil-structure interaction problems

Nonlinear soil-linear structure computational strategy is commonly accepted in the community of geotechnical engineers using advanced finite element software for solving complex soil-structure interaction problems. However, further design procedure of the structural elements is carried out using increased values of the computed elastic stress resultants. It is absolutely not clear whether this method is conservative and, therefore, whether safe or not. To tackle this problem, a fully consistent nonlinear analysis of a deep excavation protected by the diaphragm wall is analysed here. The subsoil is modelled using the Hardening Soil model, while reinforced concrete is modelled using the modified Lee-Fenves model enhanced by the Eurocode 2 (EC2)-compatible creep module, developed by the author. It is shown that the commonly used nonlinear soil-linear structure computational strategy may yield insufficient amount of reinforcement from the ultimate limit state (ULS) and serviceability limit state (SLS) points of view. A consistent and conservative method of combining fully nonlinear analysis and the rules imposed by the EC2 is proposed.