Underwater Marmaray Tunnel in Turkey Connects Europe with Asia

First suggested by the Ottoman sultan Abdülmejid in 1860, Marmaray Tunnel is a railway tunnel under the Bosphorus strait, one of the world’s busiest shipping lanes. Today, let’s take a ride through this architectural marvel.

WORDS BY- AMOG

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AS a country, Turkey is often described as a bridge between Europe and Asia due to its distinct geographical location. But now, a multi-billion dollar underwater railway tunnel will also be connecting the two continents. The Marmaray link, named by combining the Sea of Marmara with “ray,” meaning rail in Turkish, is a part of $4.5 billion, 76-kilometer mega-project launched by the Turkish Government in way back in 2004.
Alternately described as the long-lost link between Europe and Asia or the end of the city of Istanbul as we know it, it is the world’s deepest underwater railway tunnel located under the Bosphorus. Almost a mile of the 8.5-mile (13.6km) tunnel between the European and Asian sides of Turkey’s largest city is immersed under 56 metres of water.
Around 12 million people travel into and through the city of Istanbul every day and the Marmaray Project provides mass transit for the city’s population. After about 10 years of intensive research and study, 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 $4.5 billion project funding and allowed the underwater tunnel to be constructed.
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 Ayrılıkçeşme station (Asia) to Kazlıçeşme station (Europe).
It required extensive skill and engineering expertise to see a project like this see the light of the day. A Japanese-Turkish consortium led by Taisei undertook the construction contract. The firms in the consortium include Kumagai Gumi of Japan, Gama Endustri Tesisleri Imalat ve Montaj and Nurol Construction and Trade of Turkey.
This mammoth scale project would require budgets of a similar scale. It was financed by the Japan Bank for International Cooperation and the European Investment Bank. JBIC lent $950m under a long-term low-cost loan while EIB provided a €650bn soft loan.
The Bosphorus (Istanbul Strait) is crossed by a 1.4 kilometres-long earthquake-proofed immersed tube, assembled from 11 sections, each as long as 130 metres and weighing up to 18,000 tons. The sections will be placed down to 60 metres below sea level of which 55 metres will be in water and 4.6 metres in earth. This underwater tube will be accessed by bored tunnels from Kazlıçeşme on the European side and Ayrılıkçeşme on the Asian side of Istanbul.
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, tunneling methods.
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.

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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.
This amazing link commences its shuttle every day at 06:00 am. Trains run every 5 to 10 minutes during most of the day, and the last trains run all the way till midnight. Signaling 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.
The project also had to account for Turkey’s long history of violent earthquakes, and the tunnel’s position parallel to a major fault line. Transport minister Binali Yildirim has outlined the precautions, including that the tunnel is designed handle a quake of 9.0 magnitude due to construction that allows movement.
When it was finally made, forecasts estimated that by 2015 1.5 million trips per day would be made on the new route, rising to 1.7 million by 2025. Travel times were also greatly reduced for the people of Istanbul. In the opening year, travel timesaving was 25 million hours. The opening of the new rail link increased the percentage of rail passenger journeys in the Istanbul city from the 3.6% to a massive 28%.
All that still remains to be seen. But the Marmaray Tunnel has sped up trade, commerce and tourism exponentially. This might also affect real estate in and around Istanbul. But if you’re ever in Turkey and are in the mood to quickly travel from Europe to Asia, consider the Marmaray Tunnel.

The project also had to account for Turkey’s long history of violent earthquakes, and the tunnel’s position parallel to a major fault line. Transport minister Binali Yildirim has outlined the precautions, including that the tunnel is designed handle a quake of 9.0 magnitude due to construction that allows movement.

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