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Gibraltar Tunnel

Generally speaking, tunnels are underground passageways at least twice as long as they are wide and at least 0.1 miles in length or longer. Anything shorter than this is called underpass or chute. Tunnels are built beneath the mountains, seas and cities for transportation, communication and other purposes.

The ancients referred to the 9-mi. wide Strait of Gibraltar as the Pillars of Hercules, and a project is currently under way for a Herculean task — the construction of twin subterranean railway tunnels linking Spain and Morocco. The idea of a fixed link between the two continents dates from the 19th century, when railways became widespread as the new transport system.

Modern interest was revived in June 1979 during a meeting between King Juan Carlos I of Spain and King Hassan II of Morocco. Their agreement was formalized in October 1980 with the Accord de Cooperation Technique et Scientifique entre le Maroc et l’Espagne, signed in Marrakesh, Morocco.

The governments of Spain and Morocco have founded two companies to represent their interests: SNED (Societe Nationale d’Etude du Detroit) and SECEG (Sociedad espanola de Estudios para la Comunication fija a traves del Estrecho de Gibraltar).

Tunnels Laerdal Tunnel: Norway The Lćrdal Tunnel in Norway is the most spectacular tunnel because it is the longest tunnel in the world. It is a 15.2 miles long road tunnel. Its construction started in 1995 and was finished in 2000 and took the title from Gothard Road Tunnel as the world's longest road tunnel. The design of the tunnel takes into consideration the mental strain on drivers, so the tunnel is divided into four sections, separated by three large mountain caves. The caves break the routine, providing a refreshing view and allowing drivers to take a short rest. North East MRT: Singapore The 20 km long North East MRT Line (NEL) of Singapore is the most high-tech tunnel in the world. It is a Mass Rapid Transit line which is considered as the world's first fully-underground, automated and driverless rapid transit line. The line has 16 stations and will take 30 minutes to travel from one end of this line to the other end. This line is the first in Singapore to be entirely underground. Lotschberg Base Tunnel: Switzerland The 21.485 mile long Lotschberg Base Tunnel (LBT), a new railway tunnel cutting through the Alps of Switzerland some 1,312 ft below the existing Lotschberg Tunnel. It is the longest land tunnel in the world that accommodates both passenger and freight trains. Construction started in 2005 and in full scale operation by December 2007. Cu Chi Tunnels: Vietnam Many wondered why the Americans were not victorious against the communists during the Vietnam War. Well, the tunnels of Cu Chi is one of the factors why the Americans withdrawn their forces in the war. These tunnels are an immense network of connecting underground tunnels located in the Cu Chi district of Ho Chi Minh City (Saigon), Vietnam. These tunnels are part of a much larger network of tunnels that underlie much of the country. The Cu Chi tunnels were the location of several military campaigns during the war and were the Viet Cong's base of operations for the Tet Offensive in 1968. The tunnels were used by Viet Cong guerillas as hiding spots during combat, as well as serving as communication and supply routes, hospitals, food and weapon caches and living quarters for numerous guerrilla fighters. Seikan Tunnel: Japan The 33.5 mi long Seikan Tunnel of Japan is the world's longest undersea tunnel. It is a railway tunnel with a 14.5 mi portion under the seabed. It travels beneath the Tsugaru Strait connecting Aomori Prefecture on the Japanese island of Honshu and the island of Hokkaido. It is also the deepest rail tunnel in the world at or 790 ft. This title will be taken by Gotthard base Tunnel upon its completion in 2018. Channel Tunnel: UK/France Another spectacular undersea rail tunnel is the 31.4 mile long Channel Tunnel between France and United Kingdom. Its lowest point is 250 ft deep. The Channel Tunnel has the longest undersea portion of any tunnel in the world. The tunnel carries high-speed Eurostar passenger trains, Eurotunnel roll-on/roll-off vehicle transport - the largest in the world - and international rail freight trains. This tunnel is regarded as one of the "Seven Wonders of the Modern World" by the American Society of Civil Engineers in 1996. Fenghuoshan Tunnel: China With a total length of 1,338 meters long and stand at 4,905 meters above sea level, the Fenghuoshan Railway Tunnel in China is the highest railway tunnel in the world. It is part of the recently-completed Qingzang Railway that links China proper and Tibet. The Chinese word "Fenghuoshan" means "Wind Volcano". Moffat Tunnel: USA The Moffat Tunnel is a unique tunnel. It is a 6.2 miles long railroad and a water tunnel that cuts through the Continental Divide in north-central Colorado. The railroad tunnel is 24 feet and 18 feet wide. The apex of the tunnel is at 9,239 feet above sea level. The water tunnel runs parallel south of the railroad tunnel and is part of the water supple system of Denver. The tunnel was named after Colorado railroad pioneer David Moffat. Delaware Aqueduct: USA At 85 miles long and 13.5 ft wide, the Delaware Aqueduct is the world's longest continuous underground tunnel. It is the newest of the New York City aqueducts. It carries approximately half of NYC's 1.3 billion US gallons per day water demand. The Delaware Aqueduct leaks up to 35 million gallons per day. Paijanne Water Tunnel: Finland The 75 miles long Paijanne Water Tunnel located in Finland is the world's second longest continuous rock tunnel. It runs 30-100 meters under the surface in bedrock. It provides freshwater for the million people of Helsinki, Espoo, Vantaa and others in Southern Finland. Since the constant low temperature in the deep tunnel ensures high quality during transport, only minimal processing is required before use. Zhongnanshan Tunnel: China The 11.21 miles long Zhongnanshan Tunnel or Qinling Zhongnanshan Tunnel in Shaanxi Province, China is the longest two-tube road tunnel in the world. It is also the second longest road tunnel overall in the world, after the Laerdal Tunnel of Norway. The tunnel opened in 2007 which is worth 3.2 billion Yuan or US $410 million. The tunnel will reduce the traveling times from Xi'an City to Zha Shui County Town from 3 hours to 40 minutes. La Linea: Colombia La Linea or The Line is a highway tunnel currently under construction in Colombia. It will cross beneath the locally famous "Alto de La Línea" in the Cordillera Central or central range of the Andes mountains. Upon completion, it will be the longest tunnel in Latin America. Its total length will be 8,580 meters and expected to be finished in 2013. Total economic benefits are estimated to be US$40 million per annum. Eiksund Tunnel: Norway At 25,476 ft long and 942 ft deep, the Eiksund Tunnel of Norway, an undersea tunnel between the municipalities of Volda and Ulstein is the deepest undersea tunnel of its kind in the world. The tunnel joins the island of Hareidlandet with more than 40,000 inhabitants to mainland Norway. The tunnel was opened for public traffic in February 2008.

The joint venture coalition comprising TYPSA, based in Madrid, Spain, Lombardi Engineering Ltd. of Minusio, Switzerland, Ingema, headquartered in Rabat, Morocco, and Geodata SPA of Turin, Italy, was awarded the contract for environmental impact studies and preliminary project design in September 2006.

TYPSA heads the joint venture and is responsible for environmental studies, while design work is being led by Lombardi Engineering. Lombardi is presently engaged in geomechanical analyses, headed by company president and technical project director Giovanni Lombardi. Ingema cooperates in the geological and environmental studies, while Geodata handles matters related to geotechnics and tunneling methods. It is anticipated these studies will be completed by the end of 2007.

Test borings were carried out in both countries in the 1990s, said Andrea Panciera, project manager of Lombardi Engineering. “In Spain a tunnel in Tarifa about 1,312 ft. long was bored with an open tunnel boring machine. A shaft in Bolonia, Spain, approximately 262 ft. deep and another some 6.6 ft. wide and 492 ft. deep in Malabata, Morocco, were also sunk,” he stated.

A system of small tunnels and testing chambers was excavated at the bottom of the Malabata shaft, as well as a tunnel giving access to a second shaft. The latter descends to 984 ft. and leads to another short test section. “The Gibraltar tunnels will be the deepest ever excavated under the sea, and also one of the longest at approximately 25 mi., 18 mi. of which will be under water,” Panciera noted. Twin railway tunnels with a service/emergency tunnel are to be constructed. Underwater sections will go as deep as 1,640 ft. and therefore present a number of extreme challenges.

At approximately 3,281 ft. deep the Strait is unsuitable for the supports for a traditional bridge, and a floating span would interfere with the large amounts of shipping navigating this narrow bottleneck at the mouth of the Mediterranean. The very strong current and high waves also must be taken into account. A prefabricated underwater tunnel has been ruled out because of the unstable nature of the seabed. “The Gibraltar tunnels can be defined as the most complicated to be designed at present for extremely complex geological and geotechnical conditions,” Panciera pointed out. “At the lowest depth the water pore pressure is higher than the effective stress in the rock mass and the mostly marly nature of the crossed flysh formations and the soft breccia filling the two paleo-channel in the middle section of the Strait also don’t help for an ‘easy’ solution.”

As a result, the inter-continental route will therefore not traverse the shortest distance between the two countries but rather the best under prevailing conditions. The tunnels will run from Punta Paloma, near Cadiz in Spain, to Cape Malabata, near Tangier in Morocco, an area where the sea is only 984 ft. deep.

At this point design work is still under way. “The geological and geotechnical aspects have been further studied and the results are the basis for the next steps. Design is now dealing with geomechanical analyses, for which the development of particular computation models is needed due to geomechanical and hydraulical conditions, which are out of the usual ranges and combinations,” said Panciera. “The study of the building method is considering the possibilities for application of tunnel boring machines [TBM] integrated by special systems for the support of the excavation face, such as hydroshields or EPB [earth pressure balance]. Geomechanical conditions are extreme and no decisions have yet been made. They will depend also on the results of the geomechanical computations and the final design will possibly need a further investigation campaign.”

It is anticipated most of the tunnels will be excavated by earth pressure balanced shields (EPB) or other similar techniques, although the equipment to be used is not yet settled since geomechanical analyses, which form the basis for deciding equipment specifications, are still ongoing. “In addition, geological features are present, which make the situation more complicated than it was in the previous design run,” Panciera continued, “and aspects relating to the safety of the tunnel when in service are quite different as well, due to changing national and international safety standard regulations.”

The preliminary design will need the approval of the two client companies before a decision can be taken on final design and preparation of tender documents. The project schedule also will depend on aspects other than the technical, such as governmental decisions.

Financial arrangements also will needed to be addressed, and while it is too early for a reliable cost estimate, figures suggested for construction of the tunnels have ranged from $6.5 billion to $13 billion. It appears private investors will be invited to participate and it has been reported additional funding will be sought from the European Union.

Once the tunnels are built, however, they will provide numerous benefits for both countries and continents, including increased tourism revenues, rising real estate markets, and enhanced commercial and investment opportunities — not to mention the possibility of boarding a train in the north of Scotland and disembarking in Africa. As Roger Helmer, Member of the European Parliament for the East Midlands region of the UK, stated, “This is an ambitious project and a prime example of international cooperation and endeavor, which will aid economic development in both countries.”

Government officials on both sides of the Mediterranean say the tunnel would give the economies of southern Europe and North Africa an enormous boost. But the project is being driven at least as much by intangible benefits: the prospect of uniting two continents that culturally and socially remain a world apart despite their geographic proximity. In some ways, a tunnel would mirror changes that are already taking place in the form of increased trade and immigration between Europe and North Africa.

The number of Moroccan immigrants in Spain has soared in recent years; more than 500,000 live there legally, according to official statistics, while many more are undocumented residents. At the same time, droves of Europeans are rediscovering the charms of Morocco, a former Spanish and French colony that won independence in 1956. Morocco hopes to attract 10 million tourists by 2010, up from the record 6 million who visited in 2005.

Crowds pack the passenger ferries that shuttle between Tangier and Algeciras, Spain, especially in the summer, when seasonal workers travel back and forth. Mohammed Chatt, who runs a travel agency outside the port's gates in Tangier, said he doesn't expect the tunnel to be built quickly but has no doubt that millions of people would use it.

Mary Reed. Railroad Tunnels Will Link Two Continents Strait Away. Construction Equipment Guide. 5/23/2007.

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