The most effective tunnel lining? Vitreous enamel panels

If you drive up to the Austrian border along the Brenner Motorway, one of Italy’s main arteries of communication with Northern Europe, you will have to go through a great many tunnels. Understandably, every time that you enter one of these tortuous tubes you may have nightmares about getting bottled up inside it, as the dramatic sets of pictures and statistics from the latest disasters (the Mont Blanc Tunnel and the Tauerntunnel) come back to haunt you. But it is just as easy to notice the difference – both technical and psychological – between ‘normal’ tunnels (walls that are naked, peeling and stained, with poor illumination) and the ones whose interiors have been lined with light-coloured panels (cleaner, more luminous and relaxing). In one of these tunnels, there are also luminous signs that clearly mark the edges of the carriageway: the tunnel in question is the one at Funes, near Vipiteno, one of the latest to have been updated.
Today we have come to the local offices of the company that manages this motorway, Autostrada del Brennero S.p.A., to talk to Carlo Costa, a 38 year old engineer who was born in Bolzano but lives in Bressanone. Chief works engineer for the stretch from the border at the Brenner Pass down to Bolzano, Costa has concentrated much of his career on tunnels and increasing their safety ratings to European and international benchmarks.

Carlo Costa was born in Bolzano and lives in Bressanone. 38 years old and married with two children, he graduated in civil and transportation engineering from the University of Bologna in 1991 and is registered as a safety co-ordinator with the Province of Bolzano.
Costa has attended courses and symposia, in particular about safety and the problems arising from large-scale road works in reinforced concrete, and has published technical papers and memoirs in numerous symposia. From 1991 to 1995, he worked at S.E.P.I. in Trento as a technical expert specialising in design, static calculations and site management. In 1995, he won a public competition for a post of designer, site manager and safety co-ordinator during the executive phase of works with the Autostrada del Brennero S.p.A.. Since 1999, he has held the office of chief works engineer for the Brenner to Bolzano stretch of the Brenner Motorway.

“There are more than twelve kilometres of two-lane tunnels along the Brenner Motorway. The motorway runs through the Alps, which makes the problems related to these tunnels more complicated than in other places: not only is the decay of bridges and viaducts accelerated by low temperatures, cycles of freezing and thawing, massive use of chemical antifreeze agents and salts, but we also have the damp air that seeps inside the tunnels, in winter forming icicles that hang from the ceilings. The environmental conditions are made even more difficult by poor luminosity and the fact that there is no third or emergency lane.

“The first internal tunnel renovation work we did was back in 1987-88, in the tunnel at the Brenner Pass. The techniques used for waterproofing have since developed considerably and, after several serious accidents in Italy and other countries, progress has also been made on updating the safety systems, structural statics and tunnel monitoring. Since the work was done on the Brenner tunnel in 1987, we have updated the tunnels of Piè di Castello in Trento, of Fortezza and of Funes. The Fiè tunnel has already been renovated in the southbound direction, while work will be completed on the northbound section during the next winter season.
“Each of these modernisation projects is complex. We try to use every means available and work on multiple shifts, to cut the duration of the roadworks and so minimise the inconvenience for traffic. The latest work to be completed was on both the sections of the Funes tunnel and on the southbound section of the Fiè tunnel, in the stretch between Bressanone and Chiusa. A georadar inspection was conducted before the actual renovation work started: by emitting high frequency magnetic waves, this process provides a complete map of the thicknesses, detecting points where the canopy has deteriorated, any minimal spaces and the cavities that have formed between the rock and the tunnel arch. The next step was to reinforce the linings, to avoid dripping and the formation of puddles and icicles in winter. Concrete mixtures were used to fill these cavities, while the existing lining was demolished, using automated water jets capable of operating selectively on the basis of the thicknesses detected. The lining was then reconstructed by projecting reinforced waterproofing mortars, designed to be resistant to exhaust fumes, onto electrowelded reinforcement netting. Drainage work was also undertaken: storage tanks and pipes for collecting and disposing of seepage were installed along the sides of the tunnels. To complete the modernisation work in the area of accident prevention and safety in case of accidents, new kerbs and footpaths were installed, including the experimental installation of Swarovski diodes, which provide the right degree of light to indicate the boundaries of the carriageway and the traffic lanes.
“All the best installations and plant systems have been used here, of the kind suitable for tunnels more than one kilometre long: two longitudinal rows of lighting fixtures, with stronger illumination at the entrance and exit, to reduce the impact of the changeover from natural to artificial light, including adjustments to cater for the difference between night and day, as well as special counterflow lamps that highlight the contrast between any objects and the background; two rows of fluorescent emergency lamps with an independent power supply; plant systems connected to the motorway control points, where a back-up source is ready to cut in whenever there is an emergency; two groups of ventilators in every tunnel that are activated by automatic control centres in case of fire and channel all smoke and fumes towards the exit at a rate of three metres per second; sensors that monitor the rate of carbon monoxide and nitrogen and how opaque the air is; other sensors built into the tarmac that detect whether the traffic is normal, while infrared cameras monitor the tunnels even when they are full of smoke; a fire prevention system that comprises seven units for emergency fire fighting with powder extinguishers, plus a pressurised water line that does not freeze in winter, complete with a firemen’s hose. In addition, there is a computerised system that enables the parameters governing the plant systems to be adjusted from the service centre and a laser fibre cable that detects when the maximum permissible temperature has been exceeded. Last but not least, all the road signs are illuminated.”

Q: All in all, a high quality technical renovation project, in which vitreous enamel panels also cut a pretty fine figure…
“That is a very fair comment, yes. The lower part of the tunnels is lined with 3 mm thick steel panels coated with vitreous enamel. These enable the tunnels to be illuminated homogeneously and the light to be reflected; they are resistant to the antifreeze salts spread on the roads and to the exhaust gases emitted by the passing vehicles; they make it easy to clean off dust and unburned fuel particles; they are not altered by atmospheric and chemical agents, by chlorides or by exhaust gases; they are sufficiently resistant to the shocks and the increases and decreases in pressure brought about by passing vehicles and they are easy to install and remove.
“This company’s first experience with tunnel lining was in the Brenner Pass tunnel, although in that case it was not vitreous enamel that was used, but panels of reinforced concrete, drenched and coated with white polymer: because of the weight of the materials, among other things, this system created certain difficulties during the phases of production, installation and anchorage, as well as for maintenance. We ran our first tests with vitreous enamel panels in 1993-94. Since the renovation work on the tunnel of Piè di Castello, in Trento, we have extended projects of this kind and in autumn will be refurbishing the northbound carriageway of the Fiè tunnel, as I said earlier. In short: vitreous enamel panels are now the most effective answer to all our needs.”

Q: What more could be done to make this type of lining even more interesting along motorways?
“Since our first experiments and the alterations we have made to the panels, such as rounding off their edges, I would say that their performance has improved considerably. To complete the job, you should aim at having all the safety signs (sign systems, lettering, telephone numbers, emergency services, escape routes, logos and so on) already incorporated into the panels and fluorescent to make them more easily visible. That would be a very interesting option. There could also be other applications – anywhere where there is a need to combine waterproofing and a high quality of reflection with easy cleaning, such as in the lower parts of noise-reduction barriers or on the crash barriers at the tollbooths. As things stand at present, though, I would not advise you to focus on lining tunnel ceilings, which should rather be left visible: that makes it easier for us to identify any structural problems as they develop and before they get a chance to become serious. If the cost-benefit ratios are calculated correctly, there may be other interesting new applications for vitreous enamel panels. They are clearly better than plastics, which do not have all the qualities of resistance, luminosity, competitive prices and so on that I have described so far.”
On the way back from Vipiteno, your correspondent appraised the tunnels with a newly expert eye. I felt much more relaxed now, reassured by the presence of so much technology (even when you can’t see it) and by the safety systems. And I felt particularly grateful for the warm light reflected off the white vitreous enamel panels.

AUTOBRENNERO
The lowest point at which travellers can pass from north to south through the central part of the Alps without having to tackle any more significant obstacles is the Brenner Pass. Through this pass, which stands at only 1,375 metres above sea level, an endless migration of peoples has flowed since time immemorial, some driven by trade, others by wars, others by the search for new places to live.
The Second World War confirmed the importance of the Brenner Pass as an international transit point, although it also caused serious damage to be wrought on this communication artery, which had to be re-established with significant investments in renovation and extension.
The Brenner Motorway, from the Austrian border at the Brenner Pass down to the point where it feeds into the Autostrada del Sole near Modena, measures some 313 kilometres in length.
The company that manages this motorway is the Autostrada del Brennero S.p.A., whose head office is located in Trento. The President of the company is Dr. Willeit Ferdinand, while the Vice-Presidents are Giuliano Barbolino, Manuela Bruschetti, Tiziana Gualtieri and Giovanni Pavesi.
The company’s shares are held by the Autonomous Region of Trento-Aldo Adige, the Autonomous Province of Bolzano, the Autonomous Province of Trento, the Provinces of Verona, Mantua, Modena and Reggio Emilia, the Municipalities of Bolzano, Trento, Verona, Mantua, Modena and Carpi and the Chambers of Commerce of Bolzano, Trento, Verona, Mantua, Modena and Reggio Emilia.
The company’s General Manager is Dr. Massimo Occello.
The company’s Technical Manager is Professor Konrad Bergmeister.
The company has 898 employees and its 2002 balance sheet recorded a profit of € 12,222,989.

 

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