Bearing capacity in layered soil: Experimental investigations and numerical simulation

• Applicant: Dr.-Ing. Elisabeth Seibel
• Subject Area: Geotechnics, Hydraulic Engineering
• Term: since 2025
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 571134285

Even though the basic mechanisms of ground failure in homogeneous soil are now well understood, there are hardly any reliable investigations to describe the failure mode, especially in layered soils. Punching of footings through a dense top layer (sand) on soft subsoil with low bearing strength (clay) has mainly been treated as a plane-strain problem using numerical methods; meaningful experimental investigations are lacking. This is where the proposed research project comes in, with the overarching aim of analysing the complex behaviour of foundations on layered soil. To this end, experimental investigations and numerical methods will be combined. 1g tests on model strip foundations in a test box with a layered soil structure and corresponding large-scale tests on rectangular foundations in a large test pit constitute the basics of the investigation. Preliminary numerical investigations have already identified essential aspects to be considered in the model tests. In addition to standard measuring methods, the deformation behaviour should be recorded using novel, non-destructive testing and visualisation techniques. 3D photogrammetry will be used in the model box tests to identify and visualise the soil failure pattern. In the large-scale tests on rectangular foundations, the failure pattern will be identified by utilising modern fibre-optic measurement (DFOS) with suitable sensors in addition to conventional methods (excavation). The influence of the undrained shear strength of the clay layer will be captured using different types of clayey soil and variations in consistency. Experience with these clays is available from a previous DFG project. The tests will be analysed and simulated using 3D FEM calculations based on non-linear material models. After calibrating the FEM models from the test results, a detailed numerical parameter study will provide further insights into the behaviour of foundations on layered soils. The result should be a consistent, analytical calculation method that also takes into account the 3D effects of ground failure in layered soil. From this, recommendations will be derived for transfer to geotechnical practice. The expected test results can be used to calibrate and validate other material models in the future. Insights from the testing technology can also be transferred to other types of model tests and practical applications. The research project builds on previous own theoretical research on ground failure on homogeneous and layered soils. It is expected to contribute to our understanding of the behaviour of foundations on layered soils and the description of the respective failure patterns.

• DFG Programme: Research Grants