Experimental investigation of the undrained response of a shallow skirted foundation subjected to vertical compression and uplift

There is current uncertainty regarding the transient uplift capacity of skirted foundations, relative to compressive capacity, and also the time over which uplift can be sustained. In this paper, the first of these issues is addressed through half and full model tests conducted at 200g in a drum centrifuge. Undrained vertical bearing capacities in compression and uplift were measured in the full model tests, while the failure mechanisms were examined using Particle Image Velocimetry (PIV) analysis of the images captured during half model tests, aiding interpretation of the measured bearing responses. The study showed that a reverse end bearing mechanism can be mobilized in uplift and that undrained vertical bearing capacity factors of similar magnitude can be expected in compression and uplift, even for a foundation with relatively shallow embedment. The results are promising for optimizing shallow skirted foundation design for a range of offshore structures that experience transient uplift loading.