The Marmaray Bosphorus Immersed Tube Tunnel

Columbia University – January 22, 2015 – The AESA NY-NJ Section welcomed Mr. Vahan Tanal, P.E. as he presented on a recently completed rail tunnel running under the Bosphorus Strait in the city of Istanbul. The immersed tunnel is a key component of the Marmaray Project that is an upgrade of a 76 kilometer commuter rail line connecting various suburban communities on the European and Asian sides of Istanbul. His presentation covered the many challenges faced by him and his team at Parsons Brinckerhoff, a global engineering consulting firm.

Of the many major aspects of this project, one that stands out is that the Marmaray Bosphorus Immersed Tube is the first immersed tunnel ever to link the continents of Europe and Asia. This project has been under consideration for well over a hundred years but was never executed until the early 1980’s when extensive design studies were undertaken. As Vahan explained, Engineers and Contractors faced numerous challenges, many of which included dealing with a deep and narrow Bosphorus Strait, high velocity currents, fish migration and proximity to the highly seismic North Anatolian Fault not to mention unearthing centuries old artifacts dating back to prehistoric times.

The tunnel consists of eleven (11) tube sections that were cast two at a time in a dry dock at Tuzla harbor (on the Asian side). Each section was floated and sunk into place using specialized barges and instruments that allowed the contractors to position the tubes in their intended locations. Once placed, the subsequent section was joined utilizing specialized joints, which were later sealed with concrete, which ensured the tubes are watertight.

The event drew a varied crowd of professions, those in engineering, science and business. The attendees had many questions for Vahan, which focused on costs of the project, environmental considerations and various design aspects.