Construction Techniques for Deep-water Immersed Tunnel Using Real-time Sea Strait Current Forecast

The Marmaray Project (Lykke and Belkaya 2005) in Istanbul, which provides an upgraded urban railway system approximately 76 km long with a 13.4 km underground section (see Fig. 1), is under construction to overcome Istanbul’s chronic traffic congestion. Istanbul is divided into a European side and an Asian side by the Bosphorus Strait, thus the new railway system needs to cross the strait. An immersed tunnel method was applied for the construction of the tunnel, called Bosphorus Crossing Immersed Tunnel, and it is at the present time the world’s deepest immersed tube tunnel. The tunnel elements were prefabricated off-site and towed by ship to the work-site for installation and connection to the previously installed underwater elements. The remaining parts on the Asian side and the European side are being constructed using TBMs (tunnel boring machines) and are to be connected to both ends of the immersed tunnel, which consists of 11 individual submarine elements each approximately 135 m long, 15.3 m wide and 8.6 m tall. The total length of the immersed tunnel is 1,387 m and the maximum depth of the bottom of the tunnel is 60 m under the water of the Bosphorus Strait.