The A1 Autostrada, known as Autostrada del Sole (Motorway of the sun), runs for 750km from Milan to Naples, via Bologna, Florence and Rome. Not only is it the longest motorway in Italy, it is considered to be the key corridor in the country’s highway network.
To improve safety, reduce congestion and consequent environmental pollution, a new section of the A1 was proposed in 2001 through the Apennines between Bologna and Florence, known as the Variante Di Valico. This 58km ‘New A1’ would feature 23 viaducts and 22 tunnels. Towards the southern end of this extension was ‘Lot 12’ between Poggiolino to Aglio. The 4.5km route was characterised by complex geological and topographical terrain and included 3 viaducts and 5 tunnels.
Some of the tunnel portals emerged into complex Apennine clay formations, exacerbated by the presence of active or dormant landslides. The tunnel portals had to be carefully designed and constructed to stabilise, retain and consolidate the ground and required monitoring inside and outside the tunnels.
The Buttoli tunnel typified these ground conditions. Buttoni features two parallel tunnels of 490m (North) and 546m (South) with an excavated area of 190m2 . Each carriageway has a width of 11.95m per tube, thereby achieving three lanes (two running and 1 emergency) of 3.75 m wide each.
Lot 12, Variante di Valico required considerable technical and organisational commitment to stabilise and retain the portals, maintaining the land-value and cultural area of Mugello.
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