Second Tunnel Breakthrough at CastellanzaOn 18th November, 2006 the second tunnel for the project to sink underground the railway operated by Ferrovie Nord Milano through Castellanza, on the Milan Cadorna-Saronno-Busto Arsizio-Malpensa line, broke through well ahead of schedule. The first tube broke through on 19th April this year. Click here. Boring of the second tube commenced on 6th July. The project requires to excavate two parallel single-tube tunnels to a depth of 16 metres, with an inner diameter of 7,250 mm and outer diameter of 7,850 mm. The cutting diameter is 8,165 mm. The two tunnels cross under the Olona river to a depth of about four metres under the riverbed and the comprehensive length of the tunnel is 1,853 metres for one tunnel and 1,858.1 metres for the second tunnel. The bored tunnels have been each excavated by a Wirth mechanised shield boring machine. Visit www.wirth-europe.com and www.castellanza.org/default.cfm?docs=fnm/fnm_01.htmActivity at the site is non-stop 24 hours, 31 days per month and employs about 80 people, while 13 workers were working in the tunnel.The comprehensive amount of the works, including the connections with the Italian railways' network and ancillary works, is approx. EUR140 million, whereof EUR37.8 million financed by the region of Lombardy. This major scheme will increase the frequency of train connections with the Malpensa airport and therefore offer a better service to users. The project includes also two shafts (launch and receival) at the ends of the lot, roughly measuring 25 x 25 m and built in open cut using diaphragms walls; four safety exits used for escape of users and access for fire fighters, also built in open cut between diaphragm walls; two structures at the junction with the Olona river acting as ventilation duct, escape exit and access for fire fighters; and four cross passages between each bore built with traditional methods.Before passing under the Olona river, given the vicinity of the tunnel to the rail bridge and road bridge, preventive ground consolidation around the tunnel has been performed by injecting columns of jet-grouting next to each other to form a monolithic shell. The height of the upper surface of the protection works, further to preventive jet-grouting ground treatment, is such that it forms an underwater ceiling. The area of the tunnel path is situated southeast of the Verbano morainic amphitheatre. It thereby substantially comprises glacial and fluvioglacial deposits. From the surface, the ground formation is characterised by a rather typical profile made up of gravels, with sandy-silty matrix and pebbles, of varied petrography.Conventional excavation and sinking of the shafts was done with a Bobcat 442 equipped with a hydraulic hammer. After placement of steel arches, the cross passages are shotcrete lined using a Putzmeister pump and Sika silicate. Visit www.putzmeister.de and www.sika.chA TunnelTec conveyor belt has been used behind the TBM and a small dumper in the cross passages. Visit www.tunneltec.deThere has not been any settlement thanks to the injection of inert material around the profile of the bore. In September, crews set a record by excavating 733 metres. The project will cost EUR39.9 mililion. Click it/33. 48/06.