Reinforcement of bridge piling foundations

Built in the 1970s, to connect the towns of Barbâtre and Barre-de-Monts, the Noirmoutier bridge is subject to natural seafront factors: wind, sea salt, strong tides.

The Departmental Council of Vendée closely monitors this type of structure. Moreover it conducted a complete audit of this bridge in 2016. The audit revealed damage to the concrete and steel in places.
That is why the Department launched a 3-year programme to restore the structure of the bridge. In 2019, our teams were involved in the reinforcement of the foundations of piers 5 and 6 of the bridge.

These maritime works necessitated driving piles of great length (24 m long) and pouring 2,800 m3 of concrete.


Description of the works

The flyover connecting the continent to the island of Noirmoutier is 583 m long and 33.5 m high.
It is the largest engineering work in the Vendée department.
This bridge is also a busy route with over 8,700 vehicles per day and peaks in the summer of over 20,000 vehicles.

The structure dates from 1971 and is subject to major aggressive natural factors.
These factors have resulted in damage to the concrete and steel in places, mostly due to strong corrosion from salt.
In particular, the sheet piling comprising the original cofferdams showed important spillovers when the footings and piles of the piers were exposed to strong sea currents.

To consolidate the foundations of the Noirmoutier bridge, the Departmental Council of Vendée selected Charier Civil Engineering.


  • Client: Departmental Council of Vendée
  • Prime contractor: Departmental Council of Vendée
  • Duration of the works: 2018 - 2020
  • Amount: €4,000,000

Distinctive features and constraints

  • Intervention on structure in use
  • Very exposed site (strong sea current)
  • Complex access: by sea, from the bridge

Technical information

Charier retrofitted the foundations of the P5 and P6 piers.
This consisted in creating a new cofferdam by piles driven at a distance of 1.50 m to 3.50 m from the old cofferdam, then using filler concrete to fill the vacuum left between the old and new cofferdams.

Pile driving from the Cezembre self-lifting platform:
  • 900 lm of sheet piling PU28 (390 tons)
  • lengths 23 lm
  • Tie rods and walings: 117 lm
  • Concrete filling, carried out by pumping over a great distance and from a great height (from the beach, passage over the apron of the flyover and down along the piers).
  • 2,600 m3 of concrete
  • 400 lm of piping
  • Pumping height: 35 m
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