Bearing capacities of spudcan foundations in clay after penetrating through a sand layer

Layered seabeds are prevalent in many emerging provinces and sand-over-clay soil stratigraphy is particularly problematic. However, the behaviour of spudcans under combined vertical (V), horizontal (H) and moment (M) loading in such layered soil stratigraphy is not well understood and VHM yield surfaces are not defined. Centrifuge model tests in the literature have shown that a sand plug trapped underneath the spudcan increases the vertical capacity, but its effect on the horizontal and moment capacity has not yet been investigated. A set of geotechnical centrifuge test has been reported to establish the VHM yield surface of a spudcan that has been installed through a layer of sand into underlying clay. This paper is a follow-up analysis of the centrifuge testing result. Numerical simulations are presented to derive the bearing capacity factors, investigating the effect of the trapped sand plug underneath the spudcan and the backfill soil. Findings from the testing and numerical simulations are discussed.