Earth News Journal 34: Turkey Tunnel & Earthquake Resistance

One revolutionary project that has just finished construction is the Marmaray undersea tunnel in Istanbul, Turkey.

According to a November article on the National Geographic Daily News website, this visionary transportation tube was designed to allow “commuters to take a train across the Bosphorus Strait and skip Istanbul’s notoriously congested roadways.”

The first phase of the tunnel opened on October 29, marking the 90th anniversary of the formation of the Turkish Republic. Covering 8.5 miles underground, the tunnel section extends nearly 200 feet under the water of the strait, with 0.8 miles buried under the seabed.

One of the major concerns with this project is the tunnel’s close proximity to the active North Anatolian Fault, residing a mere 10 miles away from the tunnel’s location. Earthquakes are still common occurrences along this fault line, and the construction of the tunnel had to account for possible earthquakes and their respected damages.

According to Joseph Wartman, a civil engineering professor at the University of Washington in Seattle (who was not involved with the project directly but has studied its progress due to his work on earthquake-resistant design), the tunnel’s engineers “had to account for the possibility of earthquakes of magnitude as large as 7.5.” Said Wartman, “It’s really pushing the boundaries of underground construction in a seismically active area.”

Surprisingly, Wartman admitted that being in an underground tunnel during an earthquake or earth rumbling is actually “some of the safest places to be, because the level of shaking is lower below the ground compared to the surface…It may not be particularly intuitive that something deep is actually safer, but that’s the case in this situation.”

Another concern about building this underground link in the city of Istanbul is a geologic phenomenon known as liquefaction. This process “temporarily soften[s] the soil surrounding the tunnel, effectively turning that soil into a liquid.” It can actually cause the tunnel to float upwards, rendering the potential for liquefaction a critical concern for the Marmaray project.

In efforts to prevent liquefaction, engineers injected grout into the soil adjacent to the tunnel under extremely high pressures, attempting to make the soil around the tunnel denser. An increase in the density of the soil will hopefully prevent it from dislodging and rising to the surface, surmounting to major damages and destruction for the city’s people in Turkey.

As with any large-scale project, the Marmaray underground sea tunnel could contain any number of complications in the future, as natural disasters are often unpredictable in their destruction. Nonetheless, Jonathon Stewart of the University of California, Los Angeles, believes that “if an actual earthquake happens, the tunnel could well be one of the safest places in the city.”

Reflection

I’ve never heard of a project designed completely underground, as this Marmaray project in Istanbul. Honestly, I would be a little skeptical of such invention! To think, one would be traveling completely underground – in fact, under a body of water – on their way to work. That just seems highly futuristic and slightly disconcerting. I don’t know about the denizens of Istanbul, but I would be extremely cautious about using this tunnel. Maybe I’m just claustrophobic, but I would be tremendously fearful that the casing would leak, the tunnel would flood, and there would be no escape from the seemingly preventable disaster (preventable, because should humans really be traveling underneath a natural landscape, such as this body of water?). I’ll be anxious to see if this tunnel is dependable and a sustainable method of transportation in the near future. Can this tunnel prevail throughout the next few decades? As earthquakes are bound to occur along the active North Anatolian Fault, will the tunnel crumble under pressure, or will it become the latest technology in ‘hiding out’ from earthquake destruction above ground? Only time will tell. 

Ravindran, Sandeep. “Turkey’s New Undersea Tunnel Is Built to Resist Earthquakes.”National Geographic. N.p., 4 Nov. 2013. Web. 27 Feb. 2014.

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