Strange as it may seem, there is a city that lies halfway between Europe and Asia. It is Istanbul, of course, a historic city and the only metropolis that truly spans two different continents. These two continents are divided by the majestic Bosphorus Strait, which has also been one of the city’s biggest traffic problems. For millions of residents in the area, this strait is a barrier of water that created daily traffic jams and missed important appointments.
The city depended on a few completely congested bridges that created immense logistical stress. That is why the Bosphorus tunnel has become a solution to the chaos on the surface. From now on, it will be possible to travel directly under the sea to both sides of the city. Urban life in Istanbul will once again become more efficient.
The Eurasia Tunnel
The tunnel is a feat of modern civil engineering. Its official name is the Istanbul Bosphorus Road Tunnel, but many have nicknamed it the Bosphorus Tunnel. It is exclusively for vehicles, meaning it is reserved for cars and minibuses.
One of its most distinctive features is that it has two floors, like two roads stacked on top of each other. This allows four traffic lanes (two towards Asia and two towards Europe) to circulate simultaneously. This double-deck design was created to maximize the number of cars circulating while minimizing the diameter of the bore. If four lanes had been placed in parallel, they would have had to be shored up and much more care would have had to be taken with the design.
The Bosphorus Tunnel stretches for 14.6 km, 5.4 km of which are underwater. After four years of construction, the tunnel was officially opened and put into service in December 2016. This encouraged efficiency in private vehicle travel. What used to take 100 minutes stuck in surface traffic now took only 15 minutes using this tunnel. This massive time saving represents thousands of precious hours that the citizens of Istanbul now have back.
The Architectonical Achievement at a Depth of 106 Meters
The Gracia Tunnel had to fight a battle against the Earth’s crust itself. This structure was much more complex than simply drilling through soft earth. Ultimately, engineers had to contend with extreme geological conditions on the seabed, where the tunnel reaches a maximum depth of 106 meters below the surface of the Bosphorus. At this level, the water pressure is immense, so they had to design a machine specifically to deal with a mixture of gravel, dense clay, and high water saturation. Reaching depths of 106 meters and withstanding pressures of 11 bars, it offers a daily miracle of time savings.
No, depth and water pressure were not the only dangers. Istanbul is notoriously close to the North Anatolian Fault, which is fully geologically active. Seismic events (earthquakes) were not a theoretical risk, but an absolute certainty during the structure’s lifetime. For this, the builders implemented Japanese-inspired solutions: flexible seismic joints.
These were installed in the bridge’s cladding and act as massive shock absorbers.
In the event of a powerful earthquake, these special measures allow the tunnel structure to move, twist, and shift with the earth without cracking or collapsing. This is a work of proactive safety engineering.
Other tunnels in Istanbul
This road tunnel is not the only one in Istanbul, but rather complements an earlier project, the Marmaray. This other tunnel, inaugurated in 2013, is a railway tunnel that also passes under the Bosphorus. Together, these two tunnels form a comprehensive modern transport system for the megacity that straddles Europe and Asia.
The other best-known tunnel in Europe is the Eurotunnel, also known as the Channel Tunnel. This gigantic undertaking connects the United Kingdom (England) with France, crossing the cold waters of the English Channel.