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Marmaray Project

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The Marmaray Project is a major development currently being carried out in Turkey. The massive project, with an expected total cost of $1.6 billion,[1] involves linking the European and Asian portions of Istanbul, Turkey’s cultural and economic center, with a 47.4-mile (76.3-km) high capacity commuter train line.[2] The total length is the amalgamation of a new 8.3-mile (13.3-km) tunnel crossing the Bosphorus Strait (also known as the Istanbul Strait), in combination with 39 miles (63 km) of upgraded existing railway line between the Gebze and Halkali regions.

The country anticipates several favorable effects in building this new railway. Among the most significant results will be decreased traffic congestion, accelerated commuter travel times, decreased pressure on the city’s bridges, and reduced air pollution.[3]

Currently, commuters must embark on a three-hour ferry ride to get from one side of the city to the other.[4] Freight transportation is victim of a similar issue. As a train ferry’s capacity is approximately 400 tons, and a standard freight train weighs between 900 to 1,600 tons, at least three trips must be made to transport a single train, in segments, across the Bosphorus Strait; the process takes several hours.[5] With the completion of the project, travel time will be reduced to less than two hours.[6]

The project comprises several parts, including the installation of the deepest-immersed underwater railway tunnel in the world,[7] as well the improvement of the country’s current aboveground suburban railway lines. Other phases involve electrical and mechanical work, and the purchase of new rolling stock.

The immersed section of the railway tunnel, made of steel and concrete segments as long as 440 feet (134 m) and sometimes weighing up to 18,000 tons, will be under 180 feet (55 m) of water and 15 feet (4.6 m) of earth.[8]

Upon its anticipated 2012 completion, the project will include the immersed tube tunnel, bored tunnels, and cut-and-cover tunnels. The other main components will consist of three new underground stations, 37 renovated and upgraded surface stations, an operations control center, upgraded tracks, and a new third track.

Contents

[edit] Construction History

[edit] The Proposal of an Underwater Tunnel

The idea of a tunnel running under the Istanbul strait was first raised more than a century ago, in 1860.[9] The technology at the time was rudimentary, rendering construction of a tunnel on or under the seabed impossible in the deepest parts of the strait. Therefore, the plan was to build a floating tunnel on pillars that would be built on the seabed. However, the plan never materialized. Subsequent efforts were made over the following decades, including a similar plan in 1902, but designs remained largely unfeasible.

[edit] A New Technique for Modern Times

The technique for building immersed tube tunnels was developed for sewer purposes in North America in the 1894.[10] These tunnels, however, were not often used until the improvement of technology in the 1950s, facilitating large-scale projects. By the early 1980s, there was a renewed desire in Turkey to link the east and west sides of Istanbul under the strait. Following feasibility studies in 1987 and 1995, a decision was made to use the immersed tube tunnel technique for the ambitious project.

[edit] Project Funding

In 1999, a funding agreement was signed between the Republic of Turkey and the Japanese Bank for International Cooperation (JBIC). This US$117 million loan, providing approximately 35 percent of the project’s total projected cost, was allotted to the construction of the crossing through the Istanbul Strait.[11][12] In 2005, the Turkish government signed another funding agreement, this time with the European Investment Bank (EIB) for 650 million euros.[13] The rest of the funds, guaranteed by the government, are being provided through bank loans and private funding.

[edit] Marmaray Project Contractors

There are several contractors working on the project under the direction of the Parliament of the Republic of Turkey and the Ministry of Transportation.

Avrasyaconsult, the international consortium overseeing the project’s construction, is a group of four firms from Turkey and Japan, supported by additional American and Turkish consultants. The group consists of Pacific Consultants (PCI) of Japan, Yuksel Proje Uluslararasi A.S. of Turkey, Oriental Consultants of Japan, and JARTS, also from Japan. This group of contractors is working in association with American company Parsons Brinckerhoff International Inc. (PBI).[14]

Additionally, Avrasyaconsult is in association with Terzibasioglu Musavir Muhendislik Ltd. Sti. (TMM) and Yerbilimleri Etud Ve Musavirlik Ltd. Sti. (SIAL) of Turkey.[15]

The successful bidder for the Bosphorus Crossing contract is TKGN, a group consisting of TAISEI Corp. of Japan, Kumagai Gumi Co. Ltd. of Japan, Gama of Turkey, and Nurol, also from Turkey.[16]

[edit] Immersed Tube Tunnel

The immersed tunnel in the Bosphorus Strait will measure approximately 1.1 miles (1.8 km).[17] When complete, it will be an earthquake-proof, two-track rail crossing between Eminonu on the European side and Uskudar on the Asian side of Istanbul.[18]

The immersed tube tunnel (IMT) is made of components built in a dry dock or shipyard, later to be towed by purpose-built barges to the final destination. Before being immersed, each segment is outfitted with temporary bulkheads to allow them to float while the insides remain dry.

Once towed to the appropriate location, the tunnel segments are given sufficient weight to be lowered and buried in a pre-dredged trench. When connected with other prefabricated, immersed components, the joint between the segments is dewatered, resulting in the compression of a rubber sealing gasket on the section’s other end, to form a water tight seal on the joint. The segments are held in place with temporary supports until the foundation is completed, after which the trench is backfilled.

[edit] Dredging the Trench

The trench dug must be deep enough not only to contain the immersed tube tunnel, but also to ensure a protective layer of material a minimum of 6.6 feet (2 m) high can be placed on top of it. The task of clearing more than 1.3 million cubic yards (1 million m3) of material[19] is carried out using heavy dredging equipment.

The dredgers used for this task must operate at depths of approximately 190 feet (58 m),[20] which limits the type of equipment that can be used. For this reason, clamshell dredgers (CSD) and trailer suction hopper dredgers (TSHP) are used.

A clamshell dredger is a heavy machine mounted on a barge, with two or more shell-like heads, hanging from wires on the barge, that open when dropped into the water. The weight of the clamshell enables it to break through the seabed. When lifted, the shell automatically closes around the material it has collected, which will be unloaded onto surrounding barges. The most powerful clamshell dredgers are able to remove 33 cubic yards (25 m3) of material at a time;[21] they are most effective in soft to medium soil.

A trailer suction hopper dredger is a ship that tows a submerged device outfitted with a suction intake tube. This tube pumps the watery soil from the seabed into the ship. Sediment settles in the ship, while water flows from it while the ship during sailing. The full ship can then unload in a dumping area, and begin the process again. These dredgers, at their most powerful, can pump 40,000 tons of material in at one time, at a depth of approximately 230 feet (70 m).[22] They are also most effective in soft to medium soils.

In certain areas near the shore, trenches must be made in small amounts of rock. As this cannot be accomplished with dredgers, other methods must be applied. Options involve either drilling and blasting under water, or using a specialized device that can chisel through rock without blasting.

[edit] Bored Tunnels

To connect to land, the IMTs are attached to two tunnels, one going in each direction, each comprised of one track. The tunnels will be situated at Yenikapi on the European side of Istanbul, and Sogutlucesme on the Anatolian side.[23]

The tunnels are bored through rock using tunnel boring machines (TBMs), some of which have shield diameters exceeding 49 feet (15 m).[24] These passageways are connected by numerous short tunnels to enable escape into the parallel tunnel in the event of an emergency.

In areas of shallow or soft rock, the tunnels must be built using specialized methods, either with a soft-ground tunnel boring machine, or by cut-and-cover tunnel method. Essentially, the cut-and-cover tunnel method consists of excavating a trench, and then covering the trench with a roof and supports.

Certain portions of the tunnel, such as areas where trains can cross from one tunnel to the other, have an irregular shape, so different methods must be employed. Examples of these methods are drill-and-blast method, whereby a drilling jumbo bores holes filled with explosives that blast through rock; road header, using a machine with a boom-mounted cutting head, a conveyed loading device, and a crawler track; and the New Austrian Tunneling Method (NATM), involving the reliance upon surrounding rock as a “load bearing structural component”[25] to support the tunnel, as well as the application of spray concrete, known as shotcrete.

[edit] Underground Stations

In addition to the upgrading of Turkey’s current railway stations, three belowground stations will be constructed. The Sirkeci station, formed in a deep underground cavern, will likely be made using one of the techniques mentioned above; that is, drill-and-blast, road header, or NATM. The other two stations, Yenikapi and Uskudar, will be built by cut-and-cover methods.[26]

[edit] Shaky Ground

The Marmaray Project is being constructed just 12 miles (19 km) from the 745-mile- (1,199-km-) long North Anatolian Fault zone. Throughout history, this area has fallen victim to several earthquakes; two in 1999 claimed a combined 18,000 lives.[27] Over time, tremors have progressed closer to the strait, increasing the likelihood that the immersed tunnel is at risk of having to withstand a severe earthquake measuring up to 7.0 on the richter scale in the next 30 years.[28]

Since the material in which the tunnel is buried can liquefy during a quake, the sand layers are being infused with industrial grout to a depth of 80 feet (24 m) into the soil. Other safeguards include massive steel and rubber gaskets that will enable the structure to “flex like a straw in gel”[29] without breaking; and floodgates that will slam down to isolate a tube if it does break apart from the structure, keeping water from entering the stations on either side.

[edit] Progress Barriers

Throughout the life of this massive project, various obstacles have been faced. Originally projected to be complete in 2010, the project is already two years behind schedule, with a new completion date of 2012.[30] This delay is due to a major occurrence in 2005.

Before building could begin, archaeologists were brought in to survey the construction sites. In 2005, in the process of surveying, they uncovered Portus Theodosiacus, a Byzantine Harbor dating back to the times of Roman emperor Constantine the Great.[31]

Some of the artifacts that have been uncovered since the dig began are from the 6th millennium B.C.[32] Findings include pottery, shell, and bone fragments, leather sandals, anchors, hairbrushes, horse skulls, and human heads. Most notably, numerous marine vessels such as fishing, cargo, and transport boats, as well as what is possibly a Byzantine warship, have been found. These well-preserved discoveries, dating back to the seventh to 10th centuries, are the first of their kind to be uncovered.[33]

Much to the frustration of those working on the Marmaray Project, the dig has delayed construction, resulting in a cost of $1 million per day in lost revenue.[34] Yenikapi Station must be redesigned, thereby postponing other phases of construction. Archaeologists have no way of knowing how long the dig at the Yenkapi site will continue.

[edit] Equipment Used

[edit] Unique Facts

  • Deepest immersed structure in the world[35]
  • A major archaeological discovery was made at the Yenkapi construction site[36]

[edit] References

  1. Marmaray: Istanbul "cross Bosphorus" tunnel. Trains of Turkey, 2008-09-25.
  2. Marmaray: Istanbul "cross Bosphorus" tunnel. Trains of Turkey, 2008-09-25.
  3. Objective of the Marmaray Project. Marmaray, 2008-09-25.
  4. Smith, Julian Quake Fears, Ancient Finds Have Europe-Asia Tunnel on Nonstop Delay. Wired Magazine, August, 2007. (accessed: 2008-09-25)
  5. Marmaray: Istanbul "cross Bosphorus" tunnel. Trains of Turkey, 2008-09-25.
  6. Smith, Julian Quake Fears, Ancient Finds Have Europe-Asia Tunnel on Nonstop Delay. Wired Magazine, August, 2007. (accessed: 2008-09-25)
  7. Marmaray Railway Engineering Project, Istanbul, Turkey. Railway-Technology.com, 2008-09-25.
  8. Smith, Julian Quake Fears, Ancient Finds Have Europe-Asia Tunnel on Nonstop Delay. Wired Magazine, August, 2007. (accessed: 2008-09-25)
  9. Project Background. Marmaray, 2008-09-25.
  10. Project Background. Marmaray, 2008-09-25.
  11. Marmaray project: The project and its management. ITA/AITES, November, 2005. (accessed: 2008-09-25)
  12. Project Background. Marmaray, 2008-09-25.
  13. Marmaray project: The project and its management. ITA/AITES, November, 2005. (accessed: 2008-09-25)
  14. Marmaray project: The project and its management. ITA/AITES, November, 2005. (accessed: 2008-09-25)
  15. Marmaray project: The project and its management. ITA/AITES, November, 2005. (accessed: 2008-09-25)
  16. Marmaray project: The project and its management. ITA/AITES, November, 2005. (accessed: 2008-09-25)
  17. Marmaray: Istanbul "cross Bosphorus" tunnel. Trains of Turkey, 2008-09-25.
  18. Immersed Tube Tunnel. Marmaray, 2008-09-25.
  19. Dredging and Disposal. Marmaray, 2008-09-25.
  20. Dredging and Disposal. Marmaray, 2008-09-25.
  21. Dredging and Disposal. Marmaray, 2008-09-25.
  22. Dredging and Disposal. Marmaray, 2008-09-25.
  23. Marmaray: Istanbul "cross Bosphorus" tunnel. Trains of Turkey, 2008-09-25.
  24. Bored and Other Tunnels. Marmaray, 2008-09-25.
  25. Karakus, M.; Fowell, R.J. An insight into the New Austrian Tunnelling Method, 2008-09-25.
  26. Bored and Other Tunnels. Marmaray, 2008-09-25.
  27. Smith, Julian Quake Fears, Ancient Finds Have Europe-Asia Tunnel on Nonstop Delay. Wired Magazine, August, 2007. (accessed: 2008-09-25)
  28. Smith, Julian Quake Fears, Ancient Finds Have Europe-Asia Tunnel on Nonstop Delay. Wired Magazine, August, 2007. (accessed: 2008-09-25)
  29. Smith, Julian Quake Fears, Ancient Finds Have Europe-Asia Tunnel on Nonstop Delay. Wired Magazine, August, 2007. (accessed: 2008-09-25)
  30. Smith, Julian Quake Fears, Ancient Finds Have Europe-Asia Tunnel on Nonstop Delay. Wired Magazine, August, 2007. (accessed: 2008-09-25)
  31. Turkish Tunnel Project Unearths an Ancient Harbor. SpiegelOnline, May, 2006. (accessed: 2008-09-25)
  32. Smith, Julian Quake Fears, Ancient Finds Have Europe-Asia Tunnel on Nonstop Delay. Wired Magazine, August, 2007. (accessed: 2008-09-25)
  33. Smith, Julian Quake Fears, Ancient Finds Have Europe-Asia Tunnel on Nonstop Delay. Wired Magazine, August, 2007. (accessed: 2008-09-25)
  34. Smith, Julian Quake Fears, Ancient Finds Have Europe-Asia Tunnel on Nonstop Delay. Wired Magazine, August, 2007. (accessed: 2008-09-25)
  35. Marmaray Railway Engineering Project, Istanbul, Turkey. Railway-Technology.com, 2008-09-25.
  36. Smith, Julian Quake Fears, Ancient Finds Have Europe-Asia Tunnel on Nonstop Delay. Wired Magazine, August, 2007. (accessed: 2008-09-25)