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Excavating Turkey’s Hardest Rock at the Bahce-Nurdag Railway Tunnel

Southeastern Turkey’s Gaziantep province is characterized by complex fractured rock within the Eastern Anatolian Fault, and it is now the location of an important railway tunnel project. With a population of nearly 1.7 million, the province is overhauling its public transportation with a rail line between the towns of Bahçe and Nurdağı. The Bahce-Nurdag Railway Tunnel consists of two parallel 9.75 km tunnels being excavated by both NATM (850 m) and TBM (8.9 km).

Contractor Intekar Yapi Turizm Elektrik Insaat San. ve Tic. Ltd. A Robbins Single Shield TBM, 8 m in diameter, was chosen to excavate two sections of tunnel. Mixed ground conditions prevail on the project, and range from abrasive, interbedded sandstone and mudstone with quartzite veins to highly weathered shale and dolomitic limestone. The TBM has thus far encountered some of the hardest rock ever tunneled in Turkey, measuring between 136 and 327 MPa UCS.

This paper will analyze TBM performance, as well as the performance and wear of disc cutters in the difficult ground conditions. It will discuss TBM design and project logistics including onsite TBM assembly in a remote area of Turkey. Finally, it will give recommendations as to proper TBM design and cutter usage in hard, abrasive rock based on the project results.

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