Bosporus underpass with about 15,000 tubbing segments

On August 22, 2015, in front of the eyes of the Turkish Prime Minister Ahmet Davutoglu, a mix-shield pierced the target shaft wall on the European side of Istanbul exactly according to schedule. The emergence of the drilling giant was a great success of engineering for the building contractors, the Turkish-South Korean joint venture Yapı Merkezi and SK Engineering & Construction, after 16 months of driving beneath the Bosporus Strait.

Starting with a slope of 5 % from the Asian side in April 2014, the 3.34 kilometer long underpass for the two-story Eurasia road tunnel that is 106 m below the Bosporus at its deepest point, was a huge endurance test for the ultra-modern tunneling technology at water pressures of up to 11 bar; the TBM achieved record performances of up to 92 meters per week. Details about the tunnel lining with reinforced-concrete segments are given in Table 1.

The new road tunnel as part of the overall 5.4 km long crossing below the Bosporus will make a major contribution to reduce the traffic load in the city of Istanbul with its 14 million inhabitants when passing the bridge over the strait. From the end of 2016, every day about 100,000 vehicles are expected to pass from continent to continent using the 2 x 2 lanes built on top of each other; then the travel time will reduce from 100 minutes at present to just 15 minutes.

Text: Dipl.-Ing. G. Brux

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