Breakthrough on Istanbul metro 28 May 2020

After launch on its 1km long drive in mid-March, the first of four new 6.56m diameter Terratec EPBMs currently working on the Ümraniye-Ataşehir-Göztepe Metro line in Istanbul completed its first intermediate breakthrough on 20 May 2020. Its sister machine in the parallel drive, launched a month later and has been achieving consistent advance rates of up to 42m/day for the Gulermak, Nurol & Makyol JV.

Intermediate breakthrough at Atasehir station

“We have made rapid progress on the project, achieving an average of 20 rings/day for the last 10 days for both machines,” said Mesut Emre Aymir and İhsan Yağcıoğlu, Tunnel Managers for the Gulermak, Nurol & Makyol JV. This is despite the difficulties posed by Covid-19 and the relative lockdown of the city, which have seriously affected all activities and organisation of the site. “The outbreak has especially affected the commissioning of the second two machines where we have had some delays. Generally, however, we are satisfied with the performance of the Terratec machines, which have exceeded our expectations.”

The 13km-long Ümraniye-Ataşehir-Göztepe Metro (UAG) line with 11 underground stations and NATM-built connections, will form a second north to south rail corridor under the densely-populated Anatolian side of Istanbul.

The Terratec TBMs have versatile mixed-face dome-style cutterheads with an opening ratio of about 35% as well as VFD electric cutterhead drives, tungsten carbide soft ground cutting tools, that are interchangeable with 17in disc cutters, high torque screw conveyors and active articulation systems. The machines have have worked effectively at about 30m deep and through the mixed geology of low-strength sandstones, siltstones, limestones and shales.

All four of the UAG TBM drives are working from the mid-point Finans Merkezi Station. As the machines progress north and south on a 24hr basis, they install 1,500mm wide x 300mm thick precast concrete lining rings of five segments plus a key. Mucking is via continuous conveyor with TBM with segments and materials supplied by multi-service vehicles.

6.56m diameter EPBM on the UAG metro line

The UAG project is one of a number of metro lines under construction in Istanbul that will increase the current 145km metro network to more than 480km. Terratec currently has nine machines working concurrently in the city. After using Terratec machines on the Mecidiyeköy-Mahmutbey Metro line, the Gulermak, Kolin & Kalyon JV selected Terratec again for the UAG contract. The Şenbay Madencilik-Kolin-Kalyon JV also used two other 6.56m diameter Terratec EPBMs in 2017 for the Dudullu-Bostancı Metro Line.

Elsewhere in the city, there are two 6.56m diameter EPBMs working on the Halkali-Istanbul New Airport metro line for the Cengiz İnşaat, Kalyon-Kolin JV. The 31km-long line, with six new stations and connections, will form the western leg of the new M11 line that runs from the recently opened third International Airport on the European side of the city southwards to Halkali, which is also the terminus of the Marmaray railway under the Bosphorus. These machines both launched in mid-December 2019 and have excavated 2,980m and 2,680m respectively. In April and May, the TBMs achieved their best progress rates to date at 45m and 43.5m in a single day respectively.

On the other 37km-long leg of the new M11 line, a refurbished Terratec machine being operated by the Kolin-Şenbay consortium achieved a best progress rate of 46m in a single day. It is currently being prepared for its third project in the city.