Andorra Builds Dos Valires TunnelThe Principality of Andorra is in southwest Europe on the Mediterranean slope of the eastern Pyrenees between France and Spain. It is a small country, maybe 35 or 40 km in diameter, and consists of seven or eight towns, the largest of which is Andorra la Vella (21,000 inhabitants). To the north, the country borders France with a common frontier of 56.6 km and to the south it has a common frontier of 63.7 km with Spain's Catalan counties of Cerdanya, Alt Urgell and Pallars Sobirà. It is a mountainous country with narrow valleys, a surface area of 468 sq km and an average altitude above sea level of 1,996 m. The country is known for skiing, duty-free shopping, and cheap gas.Two road tunnels are currently in service in Andorra: Envalira (1 x 2,859 m), close to Pas de la Casa at the French border, and Sant Antoni (2 x 225 m). Click ad/11. Another two tunnels are under construction: Pont Pla (a 1,250 m-long single bored bidirectional tunnel, formerly named Grau de la Sabata, with a safety tunnel parallel to it) and Dos Valires, where tunnelling started recently. Civil engineering at Pont Pla is finished and equipment of the main tunnel and safety gallery is well advanced. Opening is programmed for June or July 2006. Click ad/12. Andorra has plans to build five new tunnels at short and medium terms and six others at long and very long terms. Read E-News Weekly 48/2005 for details.The Dos Valires tunnel consists of three tunnels of similar length, with a twin one-way tunnel and a service tunnel in between. The length spans 2.950 metres, awaiting to define the exact length of the cut-and-cover pieces at each mouth. The main tunnels feature a 63.9 sq m section while the service bore has a 16 sq m section. In addition, there will be 11 cross passages between the traffic tunnels and through the longitudinal service tunnel, of which eight will be pedestrian (18 sq m) and three for vehicles (34 sq m). Each main tunnel will carry two 3.5 m-wide lanes, 0.75 m shoulders and 1 m sidewalks. As for the geology, most of the tunnel crosses phyllites and metagreywacke with quartz and presence of shales at the western mouth. Some graphite and the presence of sulphates has been detected, in small proportions. The constracting JV includes Dragados, Obras Subterraneas and local construction company Trebisa. The work management has been contracted to Eurogeotecnica, Enginesa, Euroconsult and Suport Enginyers Consultors. It has been decided to execute the main tunnels with the new Austrian tunnelling method, in top heading / bench sequence by means of jumbos while the service tunnel will be driven by a 4 m-diameter TBM. There will be two or three drives, depending on the project phase. Four possible supports have been defined, which foresee the use of bolts and shotcrete in different pattern and thickness (sections I, II and III) and steel arches and invert for section IV. The shotcrete (28,442 cu m) is reinforced by Wirand FS3N steel fibres supplied by Maccaferri (1,279,900 kg). They are 33 mm-long 0.75 mm-diameter fibres, in dosage of 40 kg/cu m. The bolts will be 25 mm in diameter while the steel arches will be THNs 16.5 and 29 and HEBs 180. The project also plans mass concrete pouring in the main tunnels (38,100 cu m). The concrete plant has been supplied by Degussa. The machinery employed are a Rocket Boomer 353 ES from Atlas Copco and a Tamrock Minimatic, a Himec 9810 platform supplied by Normet (it is predicted to introduce further on another Normet platform, the 9910), a Case CX240 excavator equipped with Krupp hydraulic hammer, two Putzmeister shotcreting pumps, a Mercedes 2629 concrete mixer truck and a Manitou steel arch erector. Visit www.atlascopco.com, www.tamrock.sandvik.com, www.normet.fi, www.casece.com, www.putzmeister.de, www.maccaferri.com and www.degussa.comTecsol has executed the canopies of steel pipes at the portals. The first blasts have commenced. Tunnelling is scheduled to end in late September 2008. The muckaway method for the TBM-driven tunnel is being studied, it could possibly be done by conveyor belt, while conventional loaders usually mobilised for this type of works are used for the main tunnel. They include two Cat loaders and a Wagner ST8 wheeled loader for the first metres of the service tunnel. Visit www.cat.com. Read E-News Weekly 19/2004 & 44/2002. View pictures here. 48/05. Click image to enlarge