Consistent preload calculations for jackup spudcan penetration in clays

Onshore bearing capacity methods have conventionally been used to predict the penetration of offshore jackup spudcans into the seabed. However, the Brinch Hansen depth factor has a step change in value at the point at which the lateral dimension of a footing equals its embedment. For soft clay seabeds, where penetrations can be greater than the spudcan diameter, the step produces a spurious, unrealistic prediction of punchthrough. A small modification is proposed to the depth factor to avoid this. Some consistent modifications are proposed for several related calculations.