What does the term open/covered trench mean?

The open trench consists of digging a large opening from the surface in order to free up the space necessary for the tramway to pass. To secure this structure, a concrete slab, called a "raft", was made at the bottom of the excavation and concrete walls, called "sails", were built on either side. Once this work is completed, part of the trench is covered by a concrete structure called a "roof slab", which closes the structure.
The trench then becomes covered on this section and improvements can be made on the surface.

As part of the extension of the T7 tram, open and covered trenches will be built at both ends of the tunnel, at the level of the RN7 and the Parc de la Mairie. They will ensure the transition between the surface sections and the underground part of the tunnel.

For more information, find the methodologies of civil engineering works thanks to the video dedicated to civil engineering works.