Perforated shallow foundations are commonly used as mudmats to support subsea infrastructure such as pipeline end manifolds and terminations. The perforations may be included in the foundation design to allow water to escape during installation, or to reduce uplift resistance on decommissioning. Perforated geometries, often involving a single perforation, can also be efficient for larger gravity-based foundations. However, perforations decrease the available foundation bearing area, which reduces the capacity of the foundation during operation. This paper examines the impact of the degree of perforation on undrained vertical bearing capacity. Centrifuge model testing has been undertaken to investigate both surface and skirted foundations on undrained clay, with a perforated area ranging from 0 to 64% of the total foundation area.A corresponding numerical study has been undertaken using adaptive finite element analysis. The results allow the reduction of vertical bearing capacity for a given degree of foundation perforation to be estimated.
