Turkish joint venture contractor Gulermak-Dogus has achieved another breakthrough on the new north-south link of Istanbul’s metro, the Basak Konutlari- Bagcilar extension, holing through at Guney Sanayi station.
Best progress achieved by the 6.5m Lovat EPBM was 22m in a day, and the average rate was 16m on the drive south from Basak Konutlari station. Geology along the alignment of the twin bore project consists mainly of clays, silts and sands with a groundwater pressure up to 5 Bar.
The TBM, a RME257SE Series 23100 – one of two on the project – has completed 3,640m of tunnel, or more than half of the total run to Mahmutbey station. From Guney Sanayi, the shield will be relaunched on the 1,900m drive to Istoc station and then the 910m drive to Mahmutbey station.
In total, the JV contractor has taken three Lovat TBMs for its work on various parts of Istanbul’s expanding metro network. Apart from the 23100 models, there was previously delivered a RME275SE 17900 EPBM in late 2005 to be refurbished for work on the earlier, east-west twin bores on the Otogar-Bagcilar extension of the network.
Just beyond Bagcilar the east-west line ends, at Kirazli 1, which is also marks the south end of the Basak Konutlari- Bagcilar extension. Early this year, Lovat reported that its other RME275SE – “S3” – was driving north on the latest extension, first holing through at the next station, Kirazli, before proceeding to Mahmutbey and onward north (T&TI, March, p10).
