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Grouting works kick off for Soletanche Bachy France in Mauves-sur-Loire

At the beginning of the year, the Loire-Atlantique departmental council awarded the grouting works contract for the two bridges crossing the Loire at Mauves-sur-Loire to the consortium formed by Soletanche Bachy France (lead contractor)/ETPO/Gaïa-Terre Bleue.

Between Mauves-sur-Loire and Divatte-sur-Loire, the RD31 road crosses the Loire via two bridges: the Grand Pont de Mauves (482m) and the Pont de la Pinsonnière (90m).

The original foundations of the 11 supports for these two 19th-century structures consist of a sluice wall made up of wooden piles and sheet piles and, inside this sluice wall, wooden foundation piles driven into the alluvium. A trench, 3m deep below the low-water level at the time, was dredged and filled with lime concrete to protect the heads of the wooden piles.

This work was completed in the 1970s and 1980s, with the placement of riprap and concrete starlings on seven of the 11 piers.

Due to changes in the level of the Loire, the lime concrete is no longer constantly submerged, exposing the wooden foundations to an aerobic environment threatening their integrity, while also creating a risk of erosion of the material.


The aim of the project, designed by Terrasol, is to extend the life of the existing structure by grouting the lime concrete of the 11 bridge piles to re-establish overall cohesion. The grouting will be carried out from platforms to be installed alongside the piers from the river. Work will then be carried out to renew the riprap and repoint the piers.

The work will have to be adapted to the life-cycles of the local fauna and flora, requiring the project to be carried out over two years in 2023 and 2024 (with work undertaken between June and November). The project’s strict environmental requirements meant that a specialised design office needed to be brought in to support the consortium throughout the course of the works.

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