Nonlinear Soil Stiffness Modeling for Sustainable Foundation Design and the Green Transition of the Built Environment

Optimizing the life cycle of buildings within the green transition must also encompass foundations, which significantly influence material consumption and the embodied carbon of structures. Accurate settlement prediction is a cornerstone of sustainable design; however, engineering practice often relies on simplifications, such as assuming a constant soil deformation modulus, that lead to oversizing of foundation elements. This paper examines two types of shallow foundations, an isolated footing and a raft, founded in sandy subsoil, and compares calculation outcomes obtained using five approaches: a code-based method, parameters derived from oedometer tests, parameters from triaxial tests, and two Janbu variants that account for stiffness increasing with depth. The results reveal substantial variability in predicted settlements, ranging from underestimation with the code-based approach to overestimation with the oedometer method. The most realistic predictions were obtained using triaxial parameters and the nonlinear model, which better capture the actual deformation mechanisms of the subsoil. Although the primary aim of this study is to improve the technical accuracy of settlement prediction, these findings also demonstrate that precise geotechnical modeling naturally supports resource efficiency and contributes to sustainable construction as a secondary, yet measurable, outcome of rational design.