AbstractThe load deformation and failure behavior of shallow footings can be described in a macroelement formulation. This paper deals with the study of the failure surface and the definition and validation of plastic load deformation by single surface hardening models. The straightforward application of the plasticity theory to the soil-foundation system makes it possible to extend the given expression for the case of unsaturated soils. This paper studies a small-scale footing test on unsaturated sand for the formulation of the elastoplastic macroelement of shallow footings under a centrally applied vertical load. The influence of soil suction on different parameters associated with the macroelement is studied and calibrated against experimental results. The presented model shows good agreement with the experimental results. Finally, the limitations and still open questions of the approach are discussed in detail.