Subway project in Istanbul, Turkey

Kadikoy-Kartal subway tunnels will be the part of solution for Istanbul's heavy traffic problem. The subway consists of two underground tubes having approximately 56.1 km length. Sixteen stations are going to be constituted on the subway line. The geological formations are Trakya, Kartal, Kurtkoy, Aydos, and Dolayoba, respectively. These formations could be mostly classified as weak and/or medium rock mass classes based on geotechnical studies. The depths of the tubes also change from 18 m to 44 m due to the topographical diversity. The excavations and support of underground structures including tubes, connection tunnels, and stations in this project was started in July 2008 and completed in August 2011. The first 9 km of the tubes was driven by tunnel boring machine (TBM) while the rest of constructions were excavated by excavators and loaders. The initial support systems of the underground opening are mainly based on lattice girders, shotcrete and bolts. The aim of this paper is to give the basic stages of the subway construction project as well as the initial support systems of the underground tubes based on the geometry of the underground openings and the engineering properties of geological formation.