In order to improve traffic conditions on the A480, which crosses the Grenoble urban area, AREA wanted to upgrade the section known as TOARC Centre to three lanes. The work involved three major constraints:
- Creation of retaining walls in the Drac embankment made of riprap
- Continuity of traffic on the first two lanes of the A480
- Presence of high voltage lines on the axis of the supports
Originally, the retaining walls were to be made of sheet piles and were to increase the capacity of the A480 while securing the banks of the Drac.
The first stages of the installation of the sheet piles went smoothly, however the size of the riprap blocks forced the consortium to come up with another solution over a linear distance of more than 200 meters.
In the end, a Berliner wall solution was chosen, using metal piles installed with a drill equipped with a down-the-hole hammer.