Completion of a gigantic earthworks project

To integrate this structure into the landscape, more than 420,000 m³ of material had to be moved over a 750 m length, with excavations up to 25 m deep. This also necessitated major ground stabilisation measures. "With a view to preserving and optimising resources, the stripped earth will be reused throughout the project," explains Romain Bodson, works manager. As a reminder, the cut-and-cover is the first of eight structures that will make up this new 4.4 km road, which will considerably improve traffic flow in the municipality to the north of Luxembourg.

The gauge will have a clear height of 5 m for normal traffic and 5.50 m for exceptional transport.

After more than a year of earthworks, the structure has already begun to take shape at the bottom of this impressive trench. The first concreting operations for the foundations and walls began after the summer break, and the Ferrac workers are now busy assembling the structure's dense reinforcement. "The foundations are 1.5 m thick and the middle wall is 6.5 m high," says our site manager. The next major stage will be concreting the vault of the cut-and-cover tunnel, a real challenge, especially in terms of deadlines.

"This tool will enable three walls to be concreted simultaneously - the outer walls, the central wall and the vault - in 12.5 m sections. The difficulty lies in the sustained rhythm of one phase per week. Every Friday, around 400 m³ of concrete will be poured. On Monday, we will remove the formwork to reposition the carriage and carry out the reinforcement work, which is complex because of the geometry of the structure.

To ensure that these eight months of intensive concreting, divided into 23 phases, go as smoothly as possible, the teams have already put in place optimisation strategies. "We have designed a template for prefabricating the vault reinforcements, with more than 80 parts to be assembled. A new stage that promises to be as intense as it is exciting!