Construction methods · Caissons and marine foundations

Jack-up platforms

A barge with legs that are lowered to the seabed and then jack the hull above the waves, giving a steady drilling or piling deck in 5-40 m of water. Weather-independent once elevated, it is the platform behind most bored pile work at sea.

How bridges get built · Caissons and marine foundations · Jack-up platforms

Also called: self-elevating platform, jack-up barge, SEP

Concept diagram (TheBridgeEng)

How it is done

Tow or self-propel to the pier position; survey the seabed for the leg footprints.
Lower the legs, preload each with the hull weight to check punch-through, then jack the hull to the air gap.
Work from the deck; jack down and move to the next pier in a weather window.

Where it fits

Bored piles, drilling investigation, pile caps and pier construction at sea and in estuaries; water 5-40 m.

Where it does not

Very soft seabeds with punch-through risk, rock outcrops, strong currents beyond the leg capacity.

Plant, pace and money

PlantJack-up 30-90 m with 100-300 t crane, legs to 60 m.

ProductivityMoves take a day; the deck then works around the clock.

CostUSD 20,000-80,000 per day; the game's jack-up rate.

Risks and controls

What goes wrong

Punch-through of a leg during preload (the major jack-up accident), leg damage, collision.

Quality assurance

Site-specific leg penetration assessment, preload records, weather limits enforced.

Examples

All Gulf sea bridges, Hong Kong-Zhuhai-Macau, Incheon; the game assigns jack-ups to water piers deeper than 6 m.