Rail tunnel tube placed in Turkey

ISTANBUL, Turkey—The first immersed tube section of a new rail tunnel joining Europe and Asia was recently placed in a trench at the bottom of the Bosphorus Straits in Istanbul, Turkey, as part of the Marmaray Project. The project, with an estimated cost of $3 billion, will provide a tunnel connection between Europe and Asia.

The 450-foot-long, immersed tube tunnel elements are rectangular and consist of two adjacent ducts, each containing one track.

Avrasyaconsult, a joint venture of four firms led by Pacific Consultants International of Japan, won a six-year design-build contract in 2002 for the provision of design, tender preparation, and construction supervision of the railway crossing. PB is engineer and representative to Avrasyaconsult. The project is being financed by the Japan Bank for International Cooperation and the European Investment Bank.

The 450-foot-long, immersed tube tunnel elements are rectangular and consist of two adjacent ducts, each containing one track. Eleven tunnel elements will make up the 0.87-mile-long immersed tunnel section. Bored tunnels will be driven through rock into the ends of the immersed tunnel.

The Bosphorus tunnel will be 190-feet deep at its deepest point—deeper by 50 feet than the world’s deepest immersed tunnel (BART in San Francisco), and two to three times as deep as most other similar tunnels. The project is being designed to withstand an earthquake measuring 7.5 on the Richter scale.

The tunnel is part of an overall system of 47 miles of new and upgraded railway. The main structures and system include the immersed tube tunnel (0.87 miles), bored tunnels (6 miles), cut-and-cover tunnels (1.5 miles), at-grade structures, four new underground stations, 37 new or upgraded surface stations, an operations control center, yards, workshops and maintenance facilities, as well as 155 miles of new track. Construction on the project began in 2004 and will be completed in 2011.

PB’s involvement with the project dates to1985, when the firm was commissioned to undertake a feasibility study for the Bosphorus Crossing. The study concluded that such a connection would be feasible and cost effective. It also selected an alignment that is being used for the project today.