Robbins TBM overcomes tough Turkish geology
26 August 2020US-based TBM maker Robbins is celebrating another breakthrough, this time in Turkey. In July an 8m-diameter Robbins single shield TBM completed the first tube of the Bahçe-Nurdağı high-speed railway project in the southeast of the country.
The 8.9km-long tunnel was not an easy bore: the TBM encountered some of Turkey’s hardest and most abrasive rock, including interbedded sandstone and mudstone with quartzite veins, highly weathered shale and dolomitic limestone up to 327MPa UCS.
During the toughest conditions, the TBM’s 19in back-loading disc cutters had to be changed frequently and there was high vibration. Water ingress with fines was expected in fault lines and shear zones affected by the East Anatolian Fault.
Yet despite the challenging and abrasive rock conditions, the machine with its continuous muck conveyor system ultimately achieved up to 456m/month. The contractor was Intekar Yapi.
The new rail line between the towns of Bahçe and Nurdagi includes two parallel 9.8km tunnels being excavated by both NATM (850m) and TBM (8.9 km).
