While underground excavation work has reached nearly a quarter of the 164 km of tunnels to be built for the Lyon-Turin base tunnel, over the last few months major progress has been made in the above-ground works in France and Italy.
In France, the laying of the new railway viaduct over the Arvan River began on 10 December. The viaduct in the plain of Saint-Jean-de-Maurienne is part of the works for the railway interconnection with the historic line managed under delegated contract by SNCF Réseau.
This viaduct will allow for a change to 7 tracks, compared to the current 2.
All the works necessary for the management of excavated material are under construction. The material treatment plant in Saint-Julien-Montdenis is being assembled next to the railway junction specially created by TELT to evacuate part of the excess materials. The 5 km of conveyor belts that will transport materials between excavation sites, processing sites and storage sites are also being installed.
In Italy, the installation of the first ramp of the new Chiomonte motorway interchange on the A32 motorway is being completed, which will be used It will be used to move vehicles from the construction site of the base tunnel, thus avoiding impacting local traffic. Also at San Didero, where the new car and truck terminal is being built to replace the one in Susa, the structural element that overlays the A32 motorway was laid at the beginning of December. Now both ramps (in the direction of Turin and in the direction of Susa) will have to be connected to the motorway route in order to link up with the car and truck terminal where trucks can stop and refuel before the ascent to the Fréjus tunnel.
Underground, work is proceeding on 14 excavation faces using the conventional method. At Saint-Julien-Montdenis, excavation with explosives continues on the two fronts from the west entrance of the base tunnel, which in November progressed by 213 metres reaching a total of more than 2,560 metres on the two tubes from the entrance.
Excavation is also continuing in the sixth by-pass, which has reached a length of over 41 metres.
In the Saint-Martin-la Porte cavern, the head of the TBM was assembled, concluding the installation of the first of the seven base tunnel TBMs. This tunnel boring machine will have to dig the 9 km base tunnel parallel to the one already built by the Federica TBM. Underground excavation between Saint-Martin-la-Porte and La Praz is also progressing on the technical and logistical caverns and some sections of the base tunnel towards both Lyon and Turin.
Finally, on the Avrieux platform, the construction of the base tunnel ventilation shafts continues with the work of a robot for the automated concrete lining. This innovative system secures cavities at a depth of 350 metres without direct human intervention. After consolidating the first shaft, including installing the ‘sarcophagus’ tool to form a metal ring around the walls so that the cavities can be filled in completely, the robot is now tackling the second shaft.
