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Soletanche Bachy France carries out work to waterproof the Vioreau dam in Loire-Atlantique

As part of a vast dam modernisation project, the Loire-Atlantique departmental council has awarded lot 2 (waterproofing of the foundation and drainage) to Soletanche Bachy.

The Vioreau dam, located in the town of Joué-sur-Erdre, is primarily intended to supply water to the Nantes-Brest canal. It allows water to be stored during the winter period in order to top up the low water level during the navigation period.

 This gravity dam, built in 1834, is 13.7m high and 131.6m long, creating a reservoir holding around 7.5 million cubic meters.

Lot 2 works will begin once the reservoir has been partially emptied. The works on the upstream section of the dam include:

  • A grouting curtain 20m deep in the bedrock beneath the structure, executed using the GIN method in order to partially watertight the subsoil in contact with the ground/structure and improve the mechanical characteristics of the fractured zones,
  • A cutoff wall in secant jet grouting columns about 6m deep in the central part where an alluvial zone has been identified.

And on the downstream section of the dam:

  • A drainage network by means of oriented drains with varying azimuths drilled directly into the masonry using the Hi’Drill process.

During the call for tenders, project designers from the Eurofrance design office allowed the design of 3D plans for the various phases of work, making it possible to check the machinery’s kinematics.

The injection methodology was studied by the technical department, based on recent feedback from rock injection work.

The preparation period is coming to an end, making way for the start of injection and jet-grouting work for a period of five months from mid-April.

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