Assessment of the factors affecting the advance rate of the Tunnel Gerede, the longest and one of the most problematic water transmission tunnels of Turkey

摘要

The Gerede Tunnel, with approximately 31.6 km in length, is Turkeys longest water transmission tunnel as of 2018. The tunnel will transmit the water from the Gerede River to the Camlidere reservoir, providing drinking water to Ankara. The tunnel is divided into three sections as Umitkoy, Havullu and Camlidere, and excavations started in each section with separate tunnel boring machine (TBM-1, TBM-2 and TBM-3 respectively). The excavation, started in 2012, completed within 508 days without significant problem in the Umitkoy section having 9588 m length. In Havullu and Camlidere sections, TBMs were blocked due to high pressure water and also material ingression. This caused the progress in the tunnel to be delayed repeatedly. In addition, the harsh conditions forced to be drilled upwards after 6061th m in the Havullu section, and to be drive with another type of TBM after 7235 m in the Camlidere section. Finally, the last 8821 m was completed with the EPB machine.The daily average advance rates of TBM-1, TBM-2 and TBM-3 are respectively 18.77 m, 6.13 m and 9.37 m. For the modified EPB type TBM-4, which takes over the task of TBM-3 and TBM-2 in the last 8821 m, the advance rate is 9.56 m/day. According to the analysis, the tectonic structure, hydrogeology and TBM type are the most effective parameters on the advance rate of the Gerede Tunnel. Experiences obtained from the tunnel show that geological-tectonic-hydrogeological studies should be carried out in detail in project phase and TBM selection according to these conditions, particularly against collapse and high pressure water ingress, have vital importance.