Innovative construction solutions for tunnel safety systems
Crezza, a company specialized in concrete prefabrication, which has been working since 1992 in Italy and abroad on works of national importance, has recently been a protagonist of several motorway infrastructure projects that have brought out the ability to find tailor-made solutions and the more innovative side of the Valchiavenna reality.
New precast solutions for renovation of road tunnels
Tunnel safety is a cornerstone in the tunneling sector, and for this purpose, Autostrade per l’Italia has made itself the committer of numerous renovation and redevelopment interventions for motorway tunnels throughout the peninsula, assigning to specialists and leading national companies – including Crezza – for the respective maintenance lots. The structural renovation of old construction tunnels has required the study of customized solutions to adapt to the existing structures and meet the durability needs demanded by the client.
Crezza has responded to these specific requirements by leveraging its technological know-how and the experience gained over decades of motorway projects. The outcome was twofold:
- The development, design, and installation of new tunnel linings consisting of a precast concrete arch made up of three elements – two piers and a cap – resting on a newly rebuilt low wall;
- The realization of a metallic armour-plate for motorway tunnels to provide a tunnel lining with the thinnest possible thickness, aimed at reducing the depth of milling of the original linings.
Structural Renewal of Del Fico Tunnel and San Bernardo Tunnel on the A12 Motorway
The technical solutions conceived and developed by Crezza were carried out in the framework of two infrastructure renovation projects on Ligurian motorways, specifically for two tunnels on the A12 stretch between Genoa and Sestri Levante: the Del Fico Tunnel and the San Bernardo Tunnel.
The Del Fico Tunnel, built in the 1960s and 240 meters long, featured two artificial sections at the entrances and a natural central section, and it required the structural renovation of the tunnel’s caps, low walls, and piers, with the realisation of new lighting systems, waterproofing systems, drainage systems, and new paving. The maintenance intervention involved an initial phase of milling the original linings for partial demolition, followed by the installation of precast special lattice segments in a wedge shape: 100 concrete elements, each composed of two piers and a cap, to form a precast arch for the tunnel’s new lining. The components were prefabricated by Crezza and then installed directly on-site by the same company with remarkable speed, despite the reduced milling thickness.
The San Bernardo Tunnel, located on the same stretch of the Ligurian motorway, is shorter (91.75 meters) and underwent a structural renovation and secured, which also included waterproofing and water drainage. In this case, Crezza’s experts opted not for precast segments but for the construction of a metallic armour-plate to offer a more durable and high-performing solution to the stress factors associated with the excavation section, without forgetting the availability of small milling spaces. Crezza, in collaboration with its partners in the Temporary Association of Companies (ATI), built a galvanized metal framework consisting of curved metal beams, sheets, and fixings, which was then installed directly on-site.
Discover more details about the two motorway tunnel projects on the A12 carried out by Crezza.
