Finite element analysis of soft boundary effects on the behaviour of shallow foundations

The response of a shallow foundation has been investigated by numerical simulations in a series of lg small scale tests using the Finite Element Method. In this numerical study, special attention has been given to the influence of soft boundaries as a measure to counteract boundary effects, since limitations of space were present in the containers used for the experiments. These experiments were carried out on rigid shallow foundations on sand using strongboxes, which are routinely used in thesmall beam centrifuge at Delft University of Technology. Two soil constitutive laws were used: 1) the well-known linear elastic perfectly plastic model, and 2) a hypoplastic model. Soft boundaries have been modelled as a continuum, while soil-soft boundary interaction has been addressed by zero thickness interface elements. Model parameters have been back-figured from free field experiments, since boundary effects were considered negligible in these kinds of experiments. Finally, comparisons between numerical and experimental data showed hypoplasticity performed better than the elasto-plastic model to reproduce some aspects of mechanical boundary effects.