On the Saudi Red Sea coast, a bridge is being built over a mangrove forest without placing a single temporary structure in the water.
The method is a pile and girder integrated machine that drills, drives piles, and erects girders from one moving platform.
1. The Project
Laheq Island Bridge connects the mainland to Laheq Island in the Red Sea destination.
The total length is about 2.1 km with a 24 m wide deck.
It carries six traffic lanes plus two lanes for pedestrians and cyclists.
Foundation piles extend about 35 m below the seabed.
The key 2.17 km section of the main line crosses about 30000 m2 of mangroves.
2. Why Conventional Methods Did Not Fit
Shallow water and tidal flats usually call for a temporary steel trestle or piling barges.
A trestle means hundreds of temporary piles, a full installation and removal cycle, and direct damage to mangrove roots.
Barges need dredged channels and raise turbidity.
3. From Water to Air
The machine travels along the bridge axis supported only on completed piles, precast cap beams, and precast girders.
The front cantilever pre bores the hole and drives the pile.
A precast cap beam is then placed on the new pile group.
The girder is lifted and set, and the machine advances to the next span.
It uses a six leg support system with pressure sensing on each leg.
Each advance is limited to 0.6 m with millimetre level hydraulic adjustment.
4. Where the Machine Came From
The first machine of this type was developed in China in 2022 for an expressway expansion.
It is 92 m long, 13 m wide, and weighs 575 t.
It has a 48 m effective span and a 16 m cantilever working reach.
More than three times the efficiency of conventional single span construction was reported.
For Laheq, two new units were built.
Unit 1 entered production in June 2025, five months after the concept stage.
Unit 2 followed, and both now work toward each other from the north and south.
5. Engineering Points to Watch
Span length is governed by the machine, so the method suits long viaducts with repeated short spans.
Precast cap beams and girders must be fully standardised.
Machine loads sit on newly installed piles and cap beams, so early stage capacity and construction stage checks govern.
Pile verticality and position tolerances become critical because the deck follows directly.
6. Takeaway
A bridge always crosses an environment.
How it is built often decides more of the environmental footprint than the final structure itself.
When the foundation and superstructure move forward together from above, temporary works disappear and the ground below is left as it was.
Leaving nature in place while connecting people and places is the direction this method points to.
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