Rennes metro – Line B | France

Sensitive underground work

As part of work to extend the metro network in the Breton capital, Rennes Métropole appointed Semtcar to build line B through the heart of the city. The new, entirely automated line will be almost 15km long, including 8km of tunnel.

The tunnel route traverses various districts of Rennes and its geotechnical influence zone includes many sensitive (ancient and classified) buildings. The sensitivity of these buildings, combined with the density of construction and population inherent in any urban centre, and complex geological and geotechnical factors, required particular attention to the risk of deformation.

Adapted monitoring

In 2013, Sixense were appointed by the consortium (led by Dodin Campenon Bernard and Spie Batignolles TPCI) to provide services to monitor the structures and ground in the influence zone of work on the new metro line. Sixense conducted this monitoring with its partner Quarta.

Construction work on the stations began at the start of 2014. The monitoring team were responsible for installing all of the sensors and instrumentation at each of the nine stations and six shafts (two access shafts for the tunnel boring machine and four safety shafts), as well as data acquisition and processing throughout the project. In summer 2014, it was decided to deploy the Centaur automated topographic monitoring system in order to continuously measure surface settlement of roads in the areas above the route of the tunnel boring machine.

For four years, Sixense provided its expertise to measure the impacts of the works in real time, in order to help manage the risks associated with the construction of underground structures in this sensitive urban environment.