Tuesday 29th October 2013 has seen the inaugural opening of a new rail tunnel under the Bosphorus linking the Asian and European sides of Turkey’s capital, Istanbul. The 8.5 km tunnel is the first phase of what will eventually be the 76 km-long Marmaray rail transportation project from Gebze to Halkalı. Japan has provided $1 billion of Marmaray’s overall cost of $4 billion.
The tunnel aims to ease the infamous daily traffic jams on the two bridges that currently span the Bosphorus. It will carry up to 150,000 passengers per hour, with trains arriving as often as every 2 minutes. It is also hoped that the tunnel will one day enable the creation of a major new trade route between London and Beijing via Istanbul.
At some 60m below sea level, the 1.4 km immersed section of the tube tunnel is claimed to be the deepest in the world. Fire-resistant concrete developed in Norway was crucial for the safety of the project.
Furthermore, the tunnel lies just 18 km or so from the active North Anatolian Fault, which has posed great challenges for engineers and seismologists. The result is a tunnel now built to withstand earthquakes of up to 7.5. Its walls are made of waterproof concrete coated with a steel shell, each independently watertight. The tunnel will flex and bend much in the same way tall buildings are built to withstand earthquakes.
Heading up engineering services on the project is Avrasyaconsult, an international team made up of three partners from Japan – Pacific Consultants International, Oriental Consultants, and JARTS – and one local partner, Yüksel Proje Uluslararası. In addition, Parsons Brinckerhoff International is providing special expertise in immersed tunnels to the team, with Turkish firms TMM and SIAL advising on geotechnical engineering. New rolling stock is being supplied by Korean firm, Hyundai Rotem.
The idea was originally conceived in 1860 by Ottoman sultan, Abdoul Medjid, but was thwarted by lack of engineering know-how. Construction finally started back in 2004 but long delays have been caused by major archaeological finds. These include examples of Byzantine ships, and traces of the city wall of Constantine the Great.