Combined load capacity of a preloaded skirted circular foundation in clay

Preloaded foundation capacity has recently been a topic of major interest in offshore foundation engineering. The increase in undrained shear strength due to preloading and consolidation enables the foundation to resist a larger environmental load, thereby reducing the size of the footprint. This paper investigates the shape and size of the VHM (i.e., vertical, horizontal, and moment) capacity surface of a skirted circular foundation by comparing both the no-preload and the post-preload responses using coupled small strain finite-element analyses. The influence of the distribution of in situ undrained shear strength, the magnitude of vertical preload, and the duration of consolidation on the foundation's combined capacity are considered. An approach to estimating the post-preload VHM capacity surface of the skirted circular foundation is provided using a new set of formulations that are compared with available solutions for other foundation geometries and soil conditions.