Geotechnical design study
The project involves the restoration and reinforcement of a quarry tunnel that has been abandoned since the 1990s. This 3.4 km tunnel connects the Montagnole quarry to the Vicat cement works at La Reveriaz in the municipality of Chambéry. Originally equipped with a railway track and a locomotive, it was used to transport materials, thereby reducing road traffic associated with the operation. As part of the resumption of operations, plans are in place to install a conveyor belt to transport aggregates.
The tunnel is largely unlined and passes through marl layers that have weathered and partially collapsed over time. The project therefore involves securing the entire length of the tunnel, clearing the collapsed material, reinforcing or creating support structures in the unstable marl sections, and draining or collecting water from the rock mass.
Setec Terrasol’s assignment began with a literature review of available archive data, followed by a site survey of the gallery and surface area carried out by a geological engineer.
This preliminary analysis resulted in a geological summary formalised by a geological cross-section of the structure and the drafting of a geotechnical hypothesis note describing the methods used to justify the support structures.
In a second phase, Terrasol
produced the detailed design calculations justifying the retaining profiles to be implemented to ensure the safe operation of the tunnel.
Terrasol
also dimensioned the reinforcement of the foundation slab to which the conveyor belt supports will be anchored
