A one–dimensional elasto-viscoplastic macro-element model for creep analysis of shallow foundations on sand

Footings on sand can exhibit considerable long-term creep settlement. However, most settlement prediction methods account for creep by using either a reduced long-term equivalent sand stiffness or applying an arbitrary time correction factor. In this paper, a novel elasto-viscoplastic macro-element model for shallow foundations on sand under vertical loading is developed that provides a simple and efficient tool for footing settlement prediction explicitly accounting for creep in a realistic manner. By incorporating an isotach relationship postulated for the load-settlement behaviour of shallow foundations on sand, the macro-element is constructed based on the non-stationary flow surface theory and the time effect is incorporated using visco-plasticity. The proposed model, which requires only three input parameters, is shown to be capable of satisfactorily reproducing the load-settlement responses of footings tested in the field and in the geotechnical centrifuge at typical working loads. The proposed model can also reproduce effects seen in practice such as post-creep stiffening and settlements induced by unload-reload cycles.