As a type of shallow foundation, a mudmat serves as the seabed support structure for
subsea wells, pipeline manifolds, and pipeline terminations. The shallow foundations
are usually designed with perforations to facilitate installation and removal, but
the influence of these perforations has not been fully understood. This paper presents
a method to analyze the bearing capacities of both two-dimensional (2D) and three-dimensional
(3D) perforated shallow foundations using finite element analysis. The soil was idealized
as a Tresca material, with the undrained strength increasing linearly with depth.
The outcome indicates that perforations have nonnegligible effects on the bearing
capacity of shallow foundations. The bearing capacity decreases with increasing perforation
ratio, R, and the degree of reduction increases with the increase of the dimensionless
ratio kB/S-uo, where k is the shear strength gradient, B is the width of the foundation,
and S-uo is the shear strength at the mudline. For 2D shallow foundations, there exists
a critical perforation ratio, R-c; when the perforation ratio is lower than the critical
perforation ratio, the perforated foundation does not lose its bearing capacity. For
3D shallow foundations, the bearing capacity decreases directly with the increase
of perforation ratio, R.