The roadway under Bosphorus – Eurasia Tunnel. 

Following ideas to link Asian and European part of Istanbul by undersea tunnel and to reduce traffic problems, it has been developed of the Istanbul Strait Road Tube Crossing Project that allowed passage of the Bosphorus through a submarine tunnel, now known as Eurasia Tunnel (Avrasya Tunneli in Turkish). After the international tender, the Ministry of Transport, Maritime Affairs and Communications and AYGM entrusted ATAŞ design, construction, financing, management and finally transfer of the construction to the State, using B.O.T. (Build Operate and Transfer) model. The construction works are executed by YMSK Joint Venture, formed by the Turkish Yapı Merkezi and South Korean SK E&C (Companies that are also part of ATAŞ). In January 2013 works on site started (after a preparatory phase begun in 2011). The Eurasia Tunnel was inaugurated on December 20th, 2016, with 8 months in advance of scheduled time. The total investment amounted is approximately $ 1.25 billion. Several international construction and engineering company were involved, participating in different stages of works. Italferr together with Turkish Altnınok, in May 2014, was awarded to supervise the works as the Employer’s Representative (wich is AYGM). The project route (14.6 km) is an interintercontinental road link under Bosphorus, between the Kazliçeşme district in the European side and Göztepe districts located in the Asian area, . The underground section is about 5.4 km long, of which 3.34 km are excavated by TBM. Considering the large excavation diameter (13.71 m), the high pressures (11 bar), the heterogeneity of the soil (Trakya formation, marine sediments and erratic geology) and condition of high permeability, intervention is to be considered unprecedented and definitely problematic. Herrenknecht designed and built the TBM Mixshield Slurry used for excavation, a very versatile machine among the largest and with performance capabilities among highest in the world. Slurry technology has proven to be particularly suitable for the task. During the excavation it was possible to replace hundreds of cutterhead elements, mostly under atmospheric pressure. The machine bored section is about 3.340 m in length. Excavation started in April 2014 and ended 16 months later, on August 22nd, 2015. The average advancement was ca 7 m/day with a maximum peak of 18 m/day. The difficult excavation conditions and the stresses to which the machine components were exposed, including the presence of erratic geology, required maintenance even under hyperbaric conditions. This occurred for 4 times (total time about 6 weeks) under pressures between 8 and 10 bar. For such operations, skilled divers have been recruited. To eliminate time needed for decompression, the divers were constantly in the hyperbaric environment, working within the machine and then, during the rest period, transported by a pressurized shuttle into a special hyperbaric chamber placed outside the tunnel. The tunnel lining has an outside diameter of 13.2 m, an inside diameter of 12.0 m and the rings are consisted of 9 segments (8 + 1 key). Istanbul is located in seismic zone of high risk, near the tunnel track, about 17 km, there is the North Anatolian Fault Zone. In order to allow the tunnel to face seismic events safely, it is equipped with two seismic joints in two contact areas between Trakya and marine sediments (due to different behavior of those geological formations under earthquake conditions). Seismic joints are made by special designed rings which, in the central part allowing structural deformation under the action caused by an earthquake. The seismic joints displacement capacities are ± 75 mm for extension/contraction and ± 51 mm shear offset. The project, being particularly complex and unique, attracted international interest and recognition winning several awards.