Vacuum-anchor

In large scale oceanic civil engineering, vacuum-anchors are used to anchor gravity-based structures[1] (such as the Troll A Oil Platform) in the soft bottomed muck found on many oil bearing continental shelves and the world's shallower seas.

Fifteen storey tall continuous slip formed support legs under the Troll A Oil Platform in 1000 ft (303 m).[1]

This design is modeled on how the webbed feet of aquatic animals increase the surface area on the ground.

The lowest part of the vacuum-anchors form downward-facing cylindrical cups connecting to the legs of the gravity-based structure. The top of the cups have a valve to exhaust gases and liquids trapped from the sea bottom looking to escape. This is conceptually similar to a tall drinking glass filled with water, then inverted.

When a lifting or sideways force is applied to the cup, the weight and inertia of the enclosed solution must also be displaced. Any material that spills out of the enclosure creates a vacuum that anchors the structure to the soft bottom.