Modelling the creep of deep foundations in soft Gothenburg clays

The design of deep foundations in areas with significant background creep deformation is a challenge. In Sweden, mainly empirical methods have been used in the design of deep foundations. Generally, the predictions have been highly inaccurate, in particular with regards to the long-term deformations. Therefore, a stepwise approach is proposed, which stems from the concept of performance based design. It is shown that with the proposed approach, it is for the first time possible to perform representative back analyses of the long-term response of deep foundations in an environment with ongoing settlements. This is achieved with simplified 2D finite-element analyses using a commercially available creep model. Design assumptions and simplifications are defined based on careful back analysis of relevant case studies in the area that can be found in literature. Finally, the approach is validated by comparison with long-term monitoring of a 22-storey building on a floating piled raft.