Subway construction under the legendary Golden Horn, Istanbul

Subway construction under the legendary Golden Horn, Istanbul

Excerpt

The subway line on the European side of Istanbul connects the historical centres to the north and south of the Golden Horn. As a result, great attention was paid during construction to the preservation of heritage sites.

Sehzadebasi station is located in the old town of Istanbul inside the Walls of Constantinople. Several historic structures from the Byzantine and Ottoman eras lie in the zone of influence.

After completion of the platform tunnels, it was decided that mined tunnelling would also be used for the concourse. The aim was to minimise the proportion of cut-and-cover structures. An intermediate level connects the platform level to the station entrances. Space was also provided for mechanical and electrical installations. Pinch points due to surface structures and subway alignment had to be dealt with, leading to challenging elements of design. Additional challenges were presented by the tight limits on surface settlement and the enlargements and junctions required to connect the various shaft and tunnel cross-sections. Further investigations, feasibility studies and appraisal of options were undertaken for the dive structure, which diagonally intersects a section of Genoese city wall shortly before the bridge over the Golden Horn.