The aim of Ankara – İstanbul High-Speed Railway Project is to decrease the travel time between Ankara and İstanbul and to generally provide a faster, more comfortable and safer journey experience. The construction of the second Phase which is İnönü – Köseköy line section already started on September 2008. The geomorpho-logical and geological conditions on this 158 km section are among the roughest across the country. To give an idea, there are 33 tunnels with a total length of 55 km and 27 viaducts with a total length of 15 km. Excavation of Tunnel No.26 in this second phase started on October 2009 by us-ing NATM method. The first 297meters of the tunnel were completed with a rate of 2 m/day in chlorite and graphitic schists. It was found that a total length of 5195 meters of tunnel no.26, boring from both inlet and outlet portals can be completed within 1500 days with the same geological conditions. The estimated time is more than the required and also increases the total cost. For this reason it is realised that continuing the excavation with a tunnel boring machine (TBM) would be the optimum solution. On 1st of June a TBM with a diameter of 13,77 m. started to fix the already excavated first 297 meters. Hypothetically, the tunnel face is expected to be reached in mid Sep. 2011. In the light of additional geological and geotechnical investigations, the answers of the low penetration rate boring with NATM method tried to be highlighted and the performance of the TBM is estimated by QTBM method. By using this method the penetration rate is calculated as 8,35 m/hr and the advance rate is calculated as 0,75 m/hr for the 13,77 meter tunnel boring machine driving in chlorite and mica schists.

This content is only available via PDF.
You can access this article if you purchase or spend a download.