ABSTRACT
The objective of ASPI Network’s Tunnel Renewal Strategy is the extension of tunnel linings’ life cycle (i.e., additional 50 years) through the construction of new, structurally autonomous shell structures, replacing the original linings and ensuring suitable performance under seismic events. Since there is the need to limit the impact on highway traffic, program implementation requires innovative technical and technological solutions, that is the optimization of structural interventions, the automation and speeding up of operations, the maximization of work productivity and flexibility in terms of sites and logistics in order to allow rapid job site start-up and dismantling, by only closing at night time. For the design of pilot interventions aimed at testing alternative technical solutions, following tunnels - built in the late 1950s and early 1970s - were identified: Castello 1 left (Highway A10 Genoa - Ventimiglia), San Fermo right (Highway A09 Milan - Como) and Colle Marino left (Highway A14 Bologna - Taranto). In all the cases, preservation of original intrados profile was planned (crown radius and platform width). In Castello 1 left and San Fermo right tunnels, the new shells remain within the original lining intrados profile, after partial milling or hydrodemolition (required in presence of temporary nailing or concrete containing asbestos fibers), while in Colle Marino left the new crown is inscribed in the existing one thanks to platform lowering 65cm, which was made possible by the absence of altimetric constraints at tunnel portals. New shells consist of Steel Liner Plates in Castello 1 left, a high-performing shotcrete arch integrated with three-dimensional steel mesh panels (Ram-Arch system) in San Fermo right, and prefabricated arch slabs with rear concrete casting (on new cast in place invert) in Colle Marino left.
