Bosphorus rail link joins East and West 29 Oct 2013
Shani Wallis, TunnelTalk
It is achieved. The world's deepest immersed tube tunnel to date has opened to run the first trains and passengers between the European side and Asian side of Instanbul beneath the sea of the Bosphorus Strait in Turkey, completing what many acknowledge as one of the most significant civil engineering achievements of all time.
Fixed link under the Bosphorus inaugurated

Fixed link under the Bosphorus inaugurated

Set across one of the busiest shipping lanes in the world, beneath 58m (nearly 200ft) of the sea and within one of the most seismically active regions of the earth, the 1.4km immersed tube section of the 13.6km long crossing lies between four TBM-bored tunnel approach sections either side and between the Sirkeci Station on the European side and the Uskudar Station on the Asia side of the Bosphorus. Casting and sinking the 11 elements of the immersed tube to the 58m deep seabed trench and the docking of the downhill TBM drives into the eyes of the receiving immersed tube elements are just some of the tremendously challenging achievements of this world-leading project. A major project milestone was reached almost unnoticed in 2010 when in April, the first of the TBM drives docked successfully into the immersed tube section providing a direct connection between two continents and the ability to walk through the fixed link from the European side of Istanbul to its Asian side beneath the sea.
  • Route of the new rail connection across the Bosphorus

    Route of the new rail connection across the Bosphorus

  • Detail of the immersed tube and slurry TBM elements

    Detail of the immersed tube and slurry TBM elements

Design-build construction of the outstanding project is the achievement of a consortium led by Japanese contractor Taisei Corporation and Turkish company Gama-Nurol. Preliminary design of the immersed tube and supervision of its construction for the Turkish Government was by Parsons Brinckerhoff of the United States. JBIC, the Japan Bank for International Cooperation, provided some US$1 billion in funding for the total US$4 billion project. Funding was also provided by the European Union.

Marmaray Bosphorus rail crossing update

As well as application of NATM to excavate the Sirkeci Station and long lengths of cut-and-cover work, the project employed a Lovat EPB TBM to drive the two connecting tunnels between Sirkeci to Yenikapi Stations on the European site and four 7.8m diameter Hitachi Zosen slurry TBMs to excavate the four downhill approach tunnels and dock into the docking sleeves cast into the ends of the 1.4km long immersed tube elements.
Turkey's Prime Minister Erdogan, a former Mayor of Istanbul, and Prime Minister Shinzo Abe of Japan attended the official opening on Tuesday 29 October, which also marked the 90th anniversary of the Republic of Turkey. When fully opened, the new rail service will have the capacity to carry 75,000 people/hr across the Bosphorus and relieve crippling congestion on the two traffic bridges across the Strait. The opening of the tunnel is one of the last links, together with the Channel Tunnel undersea railway link between France and the UK, that will make it possible in the near future to travel by train from London to Beijing via Turkey.
  • Precise docking of the first TBM at the end of its drive

    Precise docking of the first TBM at the end of its drive

  • TBM docking sleeves cast into the ends of elements 1 and 11

    TBM docking sleeves cast in ends of elements 1 and 11

Determined to continue the modernisation of Turkey, Prime Minister Erdogan is also supporting construction of a third road bridge over the Bosphorus and the current TBM-bored traffic tunnel under the Strait. A 13.6m diameter Herrenknecht TBM has been dispatched to Istanbul for the road tunnel project. The Bosphorus was first crossed using a TBM in 2008 when a Herrenknecht EPBM of 6.11m diameter excavated a water tunnel beneath the Strait.
Plan of the existing, new and planned crossings of the Bosphorus

Plan of the existing, new and planned crossings of the Bosphorus

Work on the immersed tube railway tunnel project began in 2004 and was due for completion in 2009, but was held up by various factors including delays to complete archaeological excavations. Opening of the fixed link under the Bosphorus joins an elite list of leading immersed tube projects including the 6.7km immersed section of the 30km long Hong Kong-Zhuhai-Macao fixed link in Asia, the 3.7km immersed tube on the 8.2km fixed link between Busan and Geoje Island in Korea, and the agreed 19km long road and railway immersed tube fixed link across the Femernbælt between Denmark and Germany in Europe.
Tunnelling in the Mediterranean Region - TunnelCast, May 2013
Links across the waters - TunnelTalk, January 2010
Successful TBM underpass of the Bosphorus - TunnelTalk, May 2009
TBM to take on Bosphorus highway crossing - TunnelTalk, August 2013
Drill+blast jumbos on rail duty in Turkey - TunnelTalk, August 2013
China's mega sea link moves forward - TunnelTalk, Jun 2011
Femern Belt fixed link options - TunnelTalk, Jun 2009
Underground plans in South-East Europe - TunnelTalk Podcast, Apr 2012

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