 The Group / Major Projects / A29
An investment of 300 million euros funded entirely by Sanef ;
A motorway with economic objectives : linking the major Norman ports (Le Havre and Rouen) to the European motorway network ;
Tightly controlled construction cost : about 5 million euros per km ;
Minimal land occupation ;
Maximum recycling of site rubble to limit the need for quarried material ;
Between Neufchâtel-en-Bray and Amiens, the A29 motorway runs through a rural landscape made up of plateaux, dry valleys and the Bresle valley which separates the counties of Picardy and Seine-Maritime. Each carriageway has 2 lanes and a hard shoulder as standard. This stretch passes through 32 communes and has two junctions (at Poix-de-Picardie and Aumale) and one semi-interchange with the RN29 highway (at Mortemer).
This 755-metre viaduct was the subject of an architectural competition won by the architect Charles Lavigne with the contractor, Razel. At its highest point it is about 40 metres above the valley bottom; it crosses four county roads, the Paris-Le Tréport railway and the river Bresle itself. Built entirely in reinforced concrete, the deck is carried by twelve pylons. Their slender form and the thinness of the deck help the structure to fit elegantly into the valley. The deck was prefabricated on the western side of the valley: it was lifted into place in sections each 30.6 metres in length. To eliminate any risk of pollution during construction, arrangements were made to collect run-off water from the site and to seal the temporary tracks giving access to the piles.
Sanef devised an original procedure : the "Target the environment" scheme to safeguard the environment to the greatest possible extent. This procedure involves making an exhaustive inventory of the environmental constraints in the strip of land covered by the "Declaration of public utility", and resulted in two sensitive areas being identified along the motorway route as a whole, these being the Flamets-Frétils sector and the Bresle valley. In these two areas, particular attention was paid to precisely marking out the route and to the methods of construction used.
A new type of surface
The pavement surface along the Amiens / Saint-Quentin stretch and in certain truck parks was constructed using recycled aggregate, obtained from old wearing courses.
Earthworks
The construction of this stretch required the excavation of some 8 million m3 of material, and the use of 4.5 million m3 of fill. Nearly 1.4 million m3 of material will finally be disposed of.
Bridges on the A29
The stretch comprises 45 bridges as follows :
- 32 bridges over the motorway including 6 specifically for mammals ;
- 13 motorway crossings including a mixed mammal tunnel, a bridge over the A29/A28 interchange and another over the A29/A16 interchange.
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