Breakthrough on Dudullu-Bostanci

6 April 2018

Turkey – The first of four TBMs boring the Dudullu-Bostanci metro line in Istanbul broke through in early March. Contractor Senbay Madencilik-Kolin-Kalyon JV used a 6.56m Terratec EPBM, equipped with 17” disc cutters, to complete the 3.98km-long bore. The teams ended on a high, forming 19 rings in a single final shift, which translates to 26.6m of excavation in 12 hours.

The 14.2km-long line is at an average depth of 30m and passes through 13 new underground stations. Geology was mixed, with sandstones, siltstones, limestones and shales.

The tunnel was lined with RC trapezoidal segments in a 5+1 configuration, with an od of 6.3m and an id of 5.7m. These were produced by SKK JV at its factory some 10km distant from the project.

“While planning the logistics and TBM supply, we had to consider the traffic in Istanbul,” said Enver Koc, chief tunnel mechanical engineer for SKK JV. “Traffic jams are inevitable in a city of 17 million people. So, with the need for on-time segment delivery and muck removal from site, 70 percent of our operations are performed during the night shift.”

The Dudullu-Bostanci Metro project is one of five new metro lines currently being built by the Istanbul Metropolitan Municipality (IMM). Due for completion in 2019, the new lines will increase the city’s current 145km Metro network to more than 480km.