Marmaray Railway Engineering Project, Turkey
Modern civic life is the aim of one of Turkey's greatest railway engineering projects ever undertaken. The city of Istanbul, like so many others, is crippled by heavy road traffic, pollution and limited high-capacity transport systems. The Marmaray Project helps resolve many of the city's issues by providing a rail link beneath the Istanbul Strait.
It was primarily aimed at bringing great benefits to the major city, both in terms of cutting pollution - by reducing the need to use private cars - and also relying on its own electrical power generation resources rather than imported fuels.
It was anticipated that the Marmaray Project would generally aid the development of the railway system in Turkey, a country which is completing its first high-speed railway line linking the capital city Ankara with Istanbul - ultimately reducing journey times by more than three hours between these two major population centres.
Construction work of the project was scheduled to be completed in April 2009, but this was revised to 2010. The opening of the Marmaray Rail Tube Tunnel and Commuter Rail Mass Transit System was further delayed due to archaeological discoveries made at the Yenikapi construction site.
The project was finally inaugurated on 29 October 2013 coinciding with the 90th anniversary of the Turkish Republic.
Around 12 million people travel into and through the city of Istanbul everyday and the Marmaray Project provides mass transit for the city's population.
A 76.3km (48 mile) high-capacity metro style railway connects Europe and Asia by crossing the Istanbul Strait. The project includes upgrading 63km (40 miles) of suburban railway, and purchasing new rolling stock to provide the service.
Following more than a decade of studies, a funding agreement was struck in 1999 between the Republic of Turkey and the Japanese Bank for International Cooperation. This brought together 35% of the total project funding and allowed the underwater tunnel to be constructed. The total project cost was estimated at $4.5bn.
There are four main components of the Marmaray Project: the underwater railway tunnel, improvement of the Gebze-Haydarpasa and Sirkeci-Halkali suburban railway lines, electrical and mechanical works, and the procurement of new rolling stock.
The entire project is supervised by State Railroads, while the Ports and Airports Administration oversaw the project.
The construction contract was assigned to a Japanese-Turkish consortium led by Taisei. The firms in the consortium include Kumagai Gumi of Japan, Gama Endustri Tesisleri Imalat ve Montaj and Nurol Construction and Trade of Turkey.
The project was financed by the Japan Bank for International Cooperation (JBIC) and the European Investment Bank (EIB). JBIC lent $950m under a long-term low-cost loan while EIB provided a €650bn soft loan.
The Marmaray Project required the construction of a tunnel under the Istanbul Strait. The idea was first mooted in 1860 but the depth of the water negated using traditional seabed, or below, tunnelling methods.
The tunnel is the deepest immersed structure in the world, 55m below sea level. Its length is 13.6km (8.5 miles) long with 9.8km of bored tunnel, 2.4km built using cut-and-cover methods and the remaining 1.4km as a tube tunnel.
The tube tunnel carries two running lines separated by a dividing wall, pre-cast in lengths of around 100m before towing into place across the sea and dropped into place for joining together and dewatering. This process caused the water pressure at the other end of the section to compress a rubber sealing gasket, making the joint water tight. Foundations were below each section once they were lowered into place, replacing temporary foundations.
The immersed tunnel is connected to the shore by tunnels bored using tunnel boring machines (TBMs) to produce separate bores for each running line, with connections at frequent intervals for emergency use.
The scheme also required the upgrading of 63km of existing suburban railway lines, rebuilding 37 stations and building three new ones. Platforms are 225m long, the equivalent of 10 carriage lengths. The stations are based on metro style operations but are also served by heavy rail trains capable of travelling at 100km/h (60mph) with an average speed between stations of 45km/h (28mph).
The Marmaray Project now provides an east-west transport corridor with a connection at Yenkapi to the north-south metro line, also currently under construction.
The Ministry of Railways is planning to invest in rolling stock to meet the increased demands. Hyundai Rotem was awarded a contract for supplying rolling stock for the project in 2008. It delivered 440 rail sets by 2013.
The new trains have a maximum design speed of 105km/h (65.24mph) - the design speed of the railway - and are aimed at meeting an average speed between stations of 45km/h.
Signalling and communications
Signalling and communications form an important part of the new route to meet the demands of safely transporting 75,000 passengers per hour in the future with intensive operations.
Bechtel and Turkey's Enka won a €1.48bn ($1.92bn) contract to upgrade the existing railway line in Gebze and Halkali district and another line passing through the tunnel. The joint venture of Invensys Rail and Spanish-based OHL won a €195m ($254.08m) contract to supply signalling and communication solutions for the project. Transport Design International (TDI), an interior and exterior design firm, provided rolling stock designs for Hyundai Rotem.
Forecasts estimate that by 2015 1.5 million trips per day will be made on the new route, rising to 1.7 million by 2025.
Travel times will also be greatly reduced for the people of Istanbul. Travel time savings are expected to be 25 million hours by 2015.
Istanbul's railway network earlier catered for just 3.6% of all journeys in the city. Opening of the new rail link is expected to enable the city come into line with other major cities with railway transport, accommodating 28% of all passenger journeys - similar to London and New York.