Marmaray Railway Engineering Project, Turkey
The Bosphorus rail link beneath the Istanbul Strait, developed as part of Turkey's Marmaray Project, represents the first physical rail link between Europe and Asia. The 76.3km rail link was inaugurated in October 2013 on the 90th anniversary of the Turkish Republic.
The city of Istanbul, like so many others, is being crippled by heavy road traffic, pollution and limited high-capacity transport systems. The Marmaray project, apart from cutting pollution, will significantly aid the development of the railway system in Turkey, 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 delayed due to archaeological discoveries made at the Yenikapi construction site.
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. With the opening of the tunnel, commuter trains have started operating from Ayrilikçesme station (Asia) to Kazliçesme station (Europe).
The entire project was 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 involved 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 considered to be 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 consists of 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 included 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 provides an east-west transport corridor with a connection at Yenkapi to the north-south metro line, also currently under construction.
Hyundai Rotem was awarded a contract for supplying 440 rail sets for the project in 2008. The first batch of 160 cars was delivered in 2011, the second was delivered in September 2013, and the final delivery is expected in June 2014.
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. In the opening year, travel time savings are expected to be 25 million hours by 2015. The opening of the new rail link is expected to increase the percentage of rail passenger journeys in the Istanbul city from the current 3.6% to 28%.