The Mont Blanc tunnel has reopened following extensive work to repair the damage caused by the terrible fire of March 1999. Safety margins are now extremely high, especially in terms of resistance to and reaction to fire. To this end the ANAS (the Italian National Roads Authority) has published a circular containing directives for the construction of tunnels, in which stainless steel, thanks to its characteristic stability and resistance to high temperatures, is cited as the material of choice for the fabrication of, for example, the smoke extraction fans and lighting systems. The ceiling cladding, for which EN 1.4404 (AISI 316L) corrugated stainless steel sheet with a thickness of 0.5 mm was chosen, satisfies the demands of functional performances (impermeabilisation, drainage, fire insurance), durability (corrosion resistance, stability over time, minimum maintenance) and fabrication (cold forming during bending, weldability). An area of no less than 20,000 square metres has been covered. The system used to anchor the fibrecement cladding panels (3 metres high, the full length of the tunnel) is composed of anchors (made from bar stock) and profiled ribs in EN 1.4404 (AISI 316L) stainless steel.
(From âInossidabileâ? 148, June 2002)
