Mont Blanc - Aosta A5 Motorway, Courmayeur - Morgex Section - Lot 2, Italy

The Monte Bianco - Aosta project involves the construction of the Courmayeur-Morgex section, Lot N°2, part of the A5 highway connecting the Mont Blanc tunnel to the Aosta-Turin highway. This lot covers the stretch from km 0.00 to km 4+155, diverting traffic from the center of Courmayeur. The route includes an open-air section from the Entrèves area to the entrance of the "Dolonne" tunnel, and an underground section up to the Lallà viaduct.

The construction took place in a geologically complex area, requiring consolidation works and the construction of large-diameter structural wells to stabilize the excavations. The open-air section is protected from avalanches with an earth-reinforced dune, a palisade, and an avalanche barrier. Two viaducts span the Dora di Veny, measuring 270 m and 290 m respectively, with a central span of 110 m to minimize piers in the riverbed.

To protect users from avalanches, a bridge-tunnel with an A-frame structure was adopted, and the overall metal structure weighs about 5,785 tons. From the bridge, access is provided to artificial tunnels, extensions of the "Dolonne" tunnel, measuring 129.95 m and 102.80 m. The "Dolonne" tunnel features two bores of 2,847 m and 2,902 m, with six spaced lay-bys to enhance safety. The excavation was carried out using traditional methods, with explosives and mechanical excavation in rock sections.

The "Dolonne" tunnel includes a water drainage system with two D30 cm concrete pipes under the pavement, doubling the drainage capacity and facilitating repairs. This project improves road accessibility, reduces traffic congestion, and enhances road safety.