Equipment Specs
Content
Languages

Gibraltar Tunnel

From RitchieWiki

Projects > Tunnels

The Gibraltar Tunnel is a rail service tunnel straddled by two adjoining passenger rail tunnels still in the preliminary planning stages. If constructed, the tunnel will be built underneath the waters of the Strait of Gibraltar and will connect Morocco to Spain.

Such a feat is no easy task. The project is being touted as one of the biggest and most ambitious acts of civil engineering in the world since the building of the Panama Canal and the Channel Tunnel or the “Chunnel” as it has been called, connecting France to the U.K. In 2006, Lombardi Engineering Ltd. won the contract to design the underwater tunnel and is conducting preliminary geological surveys to determine the best plausible tunnel route.

Lombardi, one of 14 companies that bid on the project, is led by 80-year engineering veteran Giovanni Lombardi who has participated in a number of high-profile tunnel building projects including the Channel Tunnel[1], the Gothard Pass Tunnel, and the Mont Blanc Tunnel in Switzerland.[2] The project will take several years to complete if undertaken. As it stands now, 2025 is the projected completion date. However, a final decision to start building has yet to be determined.[3]

Contents

[edit] Construction History

The concept to bridge Morocco to Spain is one that has been considered by both countries since the 1980s when negotiations to develop a transcontinental link joining the two were first initiated. In 1991, a Spanish-Moroccan body was formed to take the idea from the concept phase to the development phase; however, early surveying of the Gibraltar Strait was hampered by sea conditions.[4]

In 2004, both countries came back to the drawing board and signed an agreement to move ahead with construction of a transcontinental link. Different options were explored but many were quickly ruled out. A bridge was impractical given that supporting pillars would have to be built at a depth of 984 feet (300 m) below sea level. A floating bridge was also not feasible due to the high volume of ships passing through the strait. An underwater tunnel constructed from prefabricated materials was also discounted since the sea bottom under the strait is unstable and underwater currents are too strong.[5] The idea for a vehicle tunnel was also written off, given that ventilation to remove exhaust gases from a tunnel that extended 8.7 miles (14 km) long would prove to be near impossible. That is when a rail tunnel similar in concept to the Channel Tunnel was considered as a viable alternative though not without its own set of complications.

[edit] Construction Road Blocks

One major obstacle is the actual depth of the strait. The best path for a route at the narrowest part of the passage is 3,000 feet[6] (900 m)[7] and therefore too deep. Another route, tentatively mapped out but not confirmed until geological testing is completed, starts about 25 miles (40 km) west at Cape Malabat in Morocco to Punta, Paloma, Spain. At an estimated 24 miles (39 km) long, with 17 miles (27 km) of that being directly located under the strait where the Atlantic Ocean and Mediterranean Sea converge, the route will be twice as long as initially conceived.[8] Even the revised route path will descend between 328 and 984 feet (100 and 300 m) below the ocean’s surface.[9]

Another difficulty with construction of such a tunnel is the actual configuration of the seabed below. The seabed in the Gibraltar Strait is much more permeable than the hard chalk seabed that was presented when drilling the Channel Tunnel and is being described as a virtual “cocktail of sand, stone and mud that make for a digger’s nightmare.”[10] Also, the fact that the tunnel will be situated on an earthquake zone directly crossing African and European tectonic plates further exacerbates complications.

Water pressure on a tunnel built so deep below the ocean’s surface is probably the biggest hurdle engineers will have to contend with. Since the seabed is so permeable, it is forcing engineers to push the tunnel down by another 300 feet (91 m) or so. At that depth, water pressure on the tunnel would make it very susceptible to heavy leaking no matter how well constructed, Andrea Panciera, chief project engineer with Lombardi, reported to the Washington Post. “This is the biggest difficulty. We have to go deep into the seabed, which is very, very soft, with a lot of water pressure on top of that.” Pressure on the tunnel will be about 46.7 tons per square foot (500 tons per m2). To combat this, powerful pumps will be needed just to avoid the tunnel from filling up with water.[11]

[edit] Project Costs

The estimated cost of attempting to construct a tunnel of this scope and magnitude given the obvious obstacles is presenting a whole other issue. A number of different figures have been suggested. With construction possibly to begin in 2008, the overall cost has been estimated at about three to 10 billion euros with both countries investing several million in intense research studies at the onset.[12] According to Spain’s transport minister 27 million euros has already been spent by the two countries on just preliminary geological surveying.[13] Private analysts figure the estimated cost of construction could range from $6.5 billion to $13 billion. Regardless, both countries expect some of the cost for the tunnel’s construction to be picked up by the European Union and the private sector.[14]

[edit] Tunnel Boring Experiments

At this stage, tunnel boring machines have been used to carry out geological surveying. In fact, due to strong underwater currents in the strait, engineers have had to actually invent new boring methods.[15]

Tunnel boring began when Morocco and Spain signed the 2004 agreement. A call for tender was launched by the joint venture company Societe Nationale d’Etudies du Detroit de Gibraltar (Morocco) and SECEG (Spain) to drill seven boreholes for geological studies.[16] Spain has also already bored an experimental tunnel measuring 560 meters long for the purpose of extracting rock samples from the strait in order to paint a more clear and accurate picture as to the seabed’s actual geological composition and a similar experiment was conducted on the Moroccan side at a depth of 300 meters.[17] Other preliminary studies have been conducted by Lombardi in 2008 with the building of a 4.8 meter tube to allow engineers to figure out just how much water will likely leak into the tunnel.[18]

[edit] Equipment Used

[edit] Unique Facts

  • The tunnel could transport up to nine million people in the first year alone with that number likely jumping up to 11 million after 10 years.
  • By 2025, the tunnel could also easily be used to transport eight million tons of goods.[19]
  • Given the hefty construction cost attached, the project could run the risk of “going into the red,” as has been the case with losses incurred in the building of the Channel Tunnel. [20]

[edit] References

  1. Swiss plan tunnel under Strait of Gibraltar. Gibraltar News Online, 2008-09-25.
  2. http://www.railpage.com.au/f-p796051.htm
  3. Whitlock, Craig. A 'Chunnel' for Spain and Morocco. Washington Post, January, 2007. (accessed: 2008-09-25)
  4. Tremlett, Giles. By train from Europe to Africa - undersea tunnel project takes a leap forward. The Guardian, October, 2006. (accessed: 2008-09-25)
  5. Swiss plan tunnel under Strait of Gibraltar. Gibraltar News Online, 2008-09-25.
  6. Whitlock, Craig. A 'Chunnel' for Spain and Morocco. Washington Post, January, 2007. (accessed: 2008-09-25)
  7. Tremlett, Giles. By train from Europe to Africa - undersea tunnel project takes a leap forward. The Guardian, October, 2006. (accessed: 2008-09-25)
  8. Short, Vicky. Spain and Morocco agree to rail tunnel under Gibraltar strait World Socialist website, January, 2004. (accessed: 2008-09-25)
  9. Tremlett, Giles. By train from Europe to Africa - undersea tunnel project takes a leap forward. The Guardian, October, 2006. (accessed: 2008-09-25)
  10. Post, Randy. Tunnel Proposed to Link Europe and Africa at Straits of Gibraltar. GeoPrac.net, February, 2008. (accessed: 2008-09-25)
  11. Whitlock, Craig. A 'Chunnel' for Spain and Morocco. Washington Post, January, 2007. (accessed: 2008-09-25)
  12. Official UK embassy in Morocco website
  13. Short, Vicky. Spain and Morocco agree to rail tunnel under Gibraltar strait World Socialist website, January, 2004. (accessed: 2008-09-25)
  14. Whitlock, Craig. A 'Chunnel' for Spain and Morocco. Washington Post, January, 2007. (accessed: 2008-09-25)
  15. Tremlett, Giles. By train from Europe to Africa - undersea tunnel project takes a leap forward. The Guardian, October, 2006. (accessed: 2008-09-25)
  16. Official UK embassy in Morocco website
  17. Morroco and Spain Seek EU Financial Assistance for Undersea Tunnel Project. Friends of Morocco, 2008-09-25.
  18. Swiss plan tunnel under Strait of Gibraltar. Gibraltar News Online, 2008-09-25.
  19. Tremlett, Giles. By train from Europe to Africa - undersea tunnel project takes a leap forward. The Guardian, October, 2006. (accessed: 2008-09-25)
  20. Whitlock, Craig. A 'Chunnel' for Spain and Morocco. Washington Post, January, 2007. (accessed: 2008-09-25)