Bearing capacity of caisson foundations under combined loading

Caisson foundations are usually subject to combined loading both under working conditions and during exceptional events such as earthquakes and tsunamis, during which the foundation experiences states of stress close to its bearing capacity. In this paper, failure envelopes of rigid and massive cylindrical caisson foundations are investigated via a set of parametric 3D push-over Finite Element (FE) numerical analyses. In particular, different (i) initial loading factors , (ii) caisson embedment ratios H/D and (iii) drainage conditions have been accounted for. The soil-caisson foundation interaction failure domains, defined in the N-Q-M generalized load space, have been derived and critically discussed providing a comparison with similar results available in the literature. Numerical results are also validated against both upper and lower bound Limit Analysis (LA) solutions. The numerical results presented in this work can be analytically interpreted and used (i) for the evaluation of the performance of a caisson under static conditions with respect to both serviceability and ultimate limit states and (ii) to develop an elastic-plastic macro element model for caisson foundations.