What are the terms of construction of the tunnel?

The construction method chosen to dig the tunnel is the tunnel boring machine.

For a tunnel boring machine to start digging, it must have a thickness of earth above it at least equal to its diameter, i.e. about ten meters in the case of a monotube (tunnel accommodating both directions of tram traffic). It is necessary to make an open and then covered trench to allow the gradual descent of the tramway. The precise length of the trench depends on the slope of the natural terrain and the maximum permissible slope threshold for the operation of the tramway: it is about 300m. The entrance shaft of the tunnel boring machine is made at the end of the cut-and-cover, once the appropriate depth has been reached. The tunnel boring machine then continues its descent until it reaches the average depth of the tunnel on the route, which is about 20 metres. These elements will be specified in the rest of the studies once the route has been stabilized. The longitudinal profile allowing the depth of the tunnel to be visualized in relation to the natural terrain over the entire route will be shared in this timeframe.