Monitoring and Maintenance of Soil Engineering Structures on the A43 Motorway.

The A43 motorway was designed to fit into the Arc en Maurienne valley. The layout was adapted to steep and very deeply-cut mountainous relief with complex geology in a site of rock, scree and alluvium. It crosses previously constructed traffic lanes and water engineering structures. The engineers faced major difficulties in ensuring the stability of structures located on delicately-balanced sites and improving the valley's environmental aspect. Through two examples of sensitive structures located on evolving sites, this article presents the monitoring operations and the maintenance work carried out to keep the motorway in service. Each of these two structures corresponds to a very different environment. The first, consisting of bridges and access embankments on compressible layers in the Rieu Sec region, was designed to support a very high amplitude of settlement. The second, consisting of a tunnel and retaining walls in the Les Sorderettes area, concerns a very steep slope exposed to instability where the hydrogeological conditions still cause problems.ing their execution and some years after being opened to traffic. The systems for monitoring and maintenance weredesigned and applied in line with the development of the respective sites, which are still classified as sensitive. For the covering abstract see ITRD E139491.