In June ‘23, a 8.0 m diameter Robbins Single Shield TBM completed its second tunnel at Turkey’s Bahçe–Nurdagˇi Railway
Geology in the second tunnel was comparable to the first, including incredibly hard and abrasive metasandstone with quartz, with an average of 220 MPa UCS and a Cerchar abrasion value of 3.87. The rock has some of the most extreme hardness and abrasiveness ever measured in Turkey.
After its first bore in the difficult ground, the machine required some inspection and repairs. “The biggest repairs we undertook with Robbins Field Service technicians were the main bearing seal change and checking and repairing of the TBM before launching it on the twin tunnel after the completion of the first tunnel. Both operations were completed in a short time due to good planning with Robbins technicians,” said Deniz Şahin, TBM Chief for contractor İntekar Yapı.
The machine began its second bore in February 2021, achieving a best monthly advance rate of 411 m. “During tunneling we performed a normal maintenance program as given in the TBM manual, and the machine had minimum downtime,” said Şahin.
The twin rail tunnels, for owner Turkish State Railways Directorate (TCDD), will provide an economic boost to a region recovering from two consecutively devastating earthquakes with magnitudes of 7.8 and 7.6 that occurred in February 2023. The project site is located very close to the intersection of two large active fault zones, the East Anatolian Fault (EAF) and Dead Sea Fault (DSF). The tunnels were inspected after the event and were found to have sustained only minor cracking in a few segments. The new rail line will provide service between the towns of Bahçe and Nurdağı and is part of the TCDD’s plan to overhaul the railway connection in southeastern Turkey by providing a shorter, faster route in one of the country’s busiest railway corridors.