Punch‐Through Instability of Jack‐Up on Seabed

A punch-through failure of a jack-up platform can occur as a result of an overall instability of the structure on the seabed even when the seabed has bearing capacity increasing with depth. The instability is analogous to the overturning of a top-heavy ship and to the Euler buckling of an inelastic strut. The instability starts when a small tilt of the structure causes an increase in the reaction on a penetrating leg which is greater than the increase in bearing resistance associated with the added penetration. The limiting weight and height to which a jack-up remains stable on a given foundation depends on the sequence of jacking and preloading of the legs.