First Breakthrough on Andora-San Lorenzo al Mare Section on Genoa-Ventimiglia Line DuallingOn 24th September, 2006 in San Bartolomeo al mare, next to Cervo torrent valley, tunnelling ended at the Collecervo-San Simone tunnel, the longest on the new Andora-San Lorenzo section. Tunnelling commenced on 12th December, 2005. The 18,825 m-long section, whereof 16,224 metres of tunnel (86%), is the second phase of the doubling of the Genoa-Ventimigla railroad. Completion of the 3,479 m-long Collecervo-San Simone tunnel marks a major milestone for the completion of the new line. Average daily progress was 12 linear metres/day. The tunnel has been bored by an Herrenknecht TBM. The machine has a total length of 150 metres including the back-up; an outside diameter of 11.84 m, a nominal diameter of 10.84 m and a net inner diameter of 10.7 m; an installed power of 4,000 kW supplied by 10 engines to rotate the cutterhead; a total installed power of 500 kW; a maximum tunnelling speed of 100 mm per minute; a progress of 1.7 m each time a segmental ring is installed and a total weight of 1,200 tonnes.The cutterhead is equipped with 64 disc cutters assembled and bolted in recesses in the axial zone of the cutterhead. The front and edge cutters are mounted independently in recesses with one or more discs arranged according to a pattern spacing them at regular distance, with the edge cutters slightly out of line with the front cutters so that they do not interfere with each other. The cutterhead is also equipped with a system of nozzles through which water or foam is sprayed to eliminate dust, to cool the cutters and to lubricate the face. Visit www.herrenknecht.comEach 400 kW engine provides energy to allow the rotation of the cutting head while 20 pairs of 40 pistons give the necessary thrust to the progress of the machine. The maximum available thrust is 10,000 tonnes/minute. A computerized system calculates the direction of excavation by comparing instantly the position of the TBM with respect to the theoretical axis. The operator can therefore correct the direction of excavation according to the indications given by all the on-board instruments. The average advance speed achieved to date is 12 metres per day, which is much more that the advance that could be achieved using traditional means. An average advance of at least 16 metres/day approximately is expected. The machine is operated by 65 technicians who work every day in 24-hour shifts. The TBM has been assembled at a base camp in Andora, uphill of the first tunnel, the Collecervo tunnel, in an immense, well-organized working area, situated between the highway viaduct and the old rail tracks, just uphill of the municipality. At the base camp, an immense shed has been erected for the production of the precast segments, adjacent to a concrete plant and a spacious storage area equipped with an overhead travelling crane. Spoil from the digging is temporarily stored near the road awaiting transport to the final dump site.The tunnel dimensions allow a complete segmental ring to be transported by two trucks. A ring is formed by six segments plus a crown segment. Each segment is 170 cm wide and weighs 8.5 tonnes. The entire production cycle, transport to the TBM and grasp inside the tunnel by the erector are based on these dimensions. The segmental lining is 40 cm thick. The segment moulds and carousel plant have been supplied by CIFA. Click here to read more about the production of the precast segments. Visit www.cifa.com At the exit of the tunnel, the TBM will continue on its way outdoor for some tens of metres in Cervo torrent valley, using an appropriate reinforced concrete structure to access to the subsequent tunnel, the 2,618 m-long Caighei tunnel, which is expected to be finished in about six months. Once that second tunnel is completed, the next phase will consist for the TBM to travel through the Castello tunnel - which is being excavated by traditional methods due to peculiar geological conditions - before commencing to bore the 3,291 m Gorleri tunnel that ends in Impero valley. When the 620 m Impero viaduct, currently under construction, is completed the TBM will drive the 354 m Bardellini tunnel. That last TBM-built tunnel will divide in two parallel tunnels for priority tracks on the Ventimiglia side.In general, all the tunnels on the section are single-bored twin-track tunnels having a crown radius of 5.25 metres. The tunnels are classified in two categories according to the tunnelling method that has been adopted. The first group includes those driven by the TBM: Collecervo-San Simone, Caighei, Gorlieri and Bardellini, for a total of about 12 km. The second group includes those dug by traditional methods: Castello, Caramagnetta, Poggi and Terra Bianca, for a total of about 3,800 metres.Considering the poor geological conditions of the subsoil, in the tunnels built by traditional digging method crews will use an excavator equipped with ripper to achieve a better profile and optimal reinforcement of the face. Fibre glass rods supplied by ATP, steel arches from Guida, a Sika shotcreting pump and welded mesh supplied by Edil Rules-Leon Bekaert are all in use to support these tunnels. The Castello tunnel is driven from the two ends and progress has reached about 40%. To date, progress at these tunnels is at 13%. Visit www.bekaert.com/building, www.sika.ch and www.atp-pultrusion.comThe tunnels built by traditional process of construction feature a cross section of about 13 metres. The net diameter after cladding has to be equal to 10.5 metres at least, given that the crown lining thickness ranges from 90 to 100 cm, and that primary reinforcements with steel arches and shotcrete have a thickness of 25-30 cm. The outer cross section is 125 sq m, whereof about 100 sq m for the top heading and 25 sq m for the invert.As far as geology is concerned, the entire section is characterised by San Remo flysch and arenaceous marly flysch with joints spaced out at a few centimetres in the most weathered stretches and at 1.50 metres in the stretches of better quality.Mucking-out in the TBM-driven tunnels is done by a conveyor belt that spans from behind the tunnel face to outside. The spoil falls through the slots and manholes in the cutterhead, then a screw collects and transfers the excavated material on the 1,000 mm-wide conveyor belt, which has a capacity of 1,500 tonnes/hour. The belt conveys the spoil until the temporary dump at the entrance. For the tunnel excavated by conventional method, the muck haulage is carried out by wheel vehicles, a Fiat Hitachi loader and 3- to 4-axle trucks. Visit www.hitachi-c-m.comThe EUR319 million contract has been awarded to a JV of Spain's Ferrovial and Italian contractor Cossi. In addition to the tunnels, the project also includes six viaducts totalling 1,430 metres (8% of the route), a station in Imperia and two stops in Andora and Diano. Visit www.ferrovial.es and www.cossi.comThe contractors and subcontractors employ 350 workers, while the construction manager, contractors and subcontractors employ 70 technicians. Work at the sites is supervised by Italferr and managed in accordance with Act 494/96 dealing with safety aspects at mobile and temporary sites. The predicted end of works is August 2008. The whole railway section, which is programmed to enter in service in July 2009, has a progress of about 25%. The total investment amounts to EUR505 million, of which EUR319 million for civil works. Click here and it/86. Visit www.rfi.it/files/varie/Andora-SanLorenzo_8.pdf and www.italferr.it 40/06.