DOI: 10.5593/sgem2011/s07.110


Monday 1 August 2011 by Libadmin2011

11th International Multidisciplinary Scientific GeoConference SGEM2011, www.sgem.org, SGEM2011 Conference Proceedings/ ISSN 1314-2704, June 20-25, 2011, Vol. 2, 271-278 pp


The railway lines in both sides of Istanbul have been connected to each other by an underwater tunnel passing through the Bosphorus. This type of tunnel is known as immersed tube tunnel. Immersed tube tunnel is a part of MARMARAY project that is continued nowadays. MARMARAY is a rail transport project in Istanbul. It consists of
the construction of an undersea rail tunnel under the Bosphorus strait. Suburban rail lines along the Sea of Marmara from Halkalı on the European side to Gebze on the Asian side will be modernized with this project.

An immersed tunnel consists of several prefabricated steel shell or concrete tubes.
These tubes are constructed on land. They are floated and moved to the immersion site.
They are installed one by one. They are lowered and connected to one another
underwater. Then, the water is pumped out and the segments are covered with the
backfill materials. An immersed tunnel is generally installed in a trench that has been
dredged previously in the bottom of a waterway between structures constructed in the
dry. All spaces between the trench bottom and the soffit of the tunnel can be a
previously prepared gravelbed, or sandbedding pumped or jetted underneath the tunnel.
Piled foundations are sometimes used, where soil conditions require them. As
construction proceeds, the tunnel is backfilled. The completed tunnel is usually covered
with a protective layer over the roof.

Survey works requires high precision in every construction project such as dam, bridge,
tunnel etc. Horizontal and vertical control of tunnels are performed by using geodetic
control points. Survey works should be performed precisely.

Keywords: Tunnel, Immersed Tube, Immersed Tube Tunnels, Geodetic Control, MARMARAY