Herstal viaducts

This project to rehabilitate the Walloon infrastructure network, started in May 2014, consisted of rehabilitating (complete replacement of structures, reinforcement of beams and piles, thickening the concrete slabs and repair work on the supporting framework) and enlarging (creation of emergency stopping lanes and an acceleration/deceleration lane) of a ‘triple’ viaduct spanning successively the Albert Canal, the Chertal site and the Meuse. Three objectives were pursued: improving the durability of the structures, reducing congestion at this point of particularly high traffic density, and optimizing user safety.

The keying, that is joining the two structurally separate road decks, was an arduous task for the team. The old upstream structure and the new structure needed to be be connected by a 1.5 m concrete slab. This delicate operation could be undertaken only after adjusting the levels and slopes of the two road decks. For this, some 1,000 tons of ballast were placed, so as to play with the elasticity of the existing structure and to induce the necessary corrections. Readers need to know here that a stream of heavy trucks can produce vertical deformations of up to about 25 cm! The other challenges were the coordination and logistics of the slab, as well as accessibility and navigation, given the need to keep road and canal traffic flowing at all times. For this reason the work was divided into six successive phases in order to maintain three traffic lanes operating in both directions during most of the duration of the site.