Metro Istanbul - Kadiköy, an Underground Station Close to the Sea and Below a Historical Building

On the Asian side of Istanbul a 21.7 km long new metro system with 16 underground stations will run from the Bosphorus shipping pier Kadiköy to the suburb district Kartal in the southeast. The single track running tunnels will be constructed by means of two single shield TBM. Stations and switch tunnels are constructed with NATM. Driving at a depth of 25 to 35 m the rock is weathered and intensely fractured by tectonic processes. The area of Kadiköy station was a shallow harbor in the Ottoman time and has been filled up in the beginning of 20th century. Special care had to be taken to minimize settlements of the foundation of a historical building. In order to investigate the influence of the tunnel construction on settlements and to achieve an economic design of the primary lining at intersections a three-dimensional time-dependent finite element model has been developed. The Eurocode-based design concept and numerical results are presented in some detail. The chosen design concept including a 30 cm shotcrete primary lining and additional protection by a pipe-umbrella guaranteed a safe and economic construction and prevented damage to the historical building.