In April 1999, rapid spud can penetration was experienced while pre-loading a jack up rig at the Anding–A platform. The bow leg punched through a stiff clay layer at 11 meters, which caused the hull to tilt, resulting in all the three legs becoming bent and damaged.
After repairing the rig, it was towed back to the platform, and 26 inch diameter holes drilled in a grid pattern to break up and weaken the stiff clay layer below the aft spud can foot prints. This procedure subsequently allowed the rig to be pre-loaded and jacked up safely.
This "Swiss Cheese" technique of pilot hole drilling has been found successful in allowing an independent leg jack-up rig to be safely positioned on locations where the presence of a thin layer of stiff clay, underlain by soft / weaker soils, indicates the potential for punch-through. It is may also be useful in enabling a jack-up rig to be positioned on a location where there is a compatibility problem between rig spud-can spacing, and existing footprints.