Construction of a wildlife crossing over the A3 motorway

As part of the project to widen the A3 motorway to 2x3 lanes, the Ponts et Chaussées have entrusted us with the construction of a new ecoduct that will allow wildlife to travel in complete safety.

Located on the Franco-Luxembourg border, the structure not only has impressive dimensions, but also an original geometry. The ecoduct will be shaped like an arch, tapering at its highest point. It will be made up of two very wide piers on either side of the roadway. These parameters make its construction all the more complex, especially as the work will be carried out close to the motorway, where traffic is heavy.

With a length of 67 m, the ecoduct will span the tracks over a width of 40 m and reach a height of 8.60 m.

The structure is made up of a dense metal and concrete structure, the vaulted piers of which have been produced using a curved concreting carriage that allows the walls to be 12.5 m long.

Once the base of the vaults was complete, formwork tables were installed above the road to proceed with the reinforcement and concreting of the vault. An operation to be carried out in September 2023 that began in the early hours of the morning

They are in fact three-dimensional, revolving around a longitudinal axis and varying in height from 1.5 to 4 m. This involved meticulous reinforcement and formwork work, which was also made to measure. They required 120 m³ of concrete each.

Once the concreting was complete, the waterproofing, guardrail, safety barrier, backfill and landscaping work followed, while the site installations gradually disappeared from view with the dismantling of the two assembly tables and the crane, and then the resumption of traffic under the motorway.