Terratec has delivered two 6.56m diameter EPBMs to Turkey for the ongoing expansion of the Istanbul metro system in Turkey and a new 3.2m diameter EPBM to Bangkok, Thailand, for the Phra Khanong cable tunnel project.
The new machines to Turkey will be used alongside two existing Terratec TBMs by the Şenbay Madencilik-Kolin-Kalyon JV on the €1.4 billion Dudullu-Bostancı Istanbul Metro Line project.. The14.2km-long lineand its 13 new stations runs north to south across the densely-populated Anatolian side of the city, and will be located entirely underground.
Members of the joint venture were impressed with the performance of the Terratec machine being used by the Gülermak-Kolin-Kalyon JV on the new Mecidiyeköy-Mahmutbey Metro Line, in Instanbul during a site visit and decided to employ two further Terratec machineson their second project for the Istanbul Metropolitan Municipality (IMM).
The Terratec TBMs have a mixed-face cutterhead with an opening ratio of about 35% which are designed to manage the rock and soil formations of Istanbul’s geology, and are equipped with VFD electric cutterhead drives, soft ground cutting tools, that are interchangeable with 17in disc cutters, high torque screw conveyors, and active articulation systems.
The tunnel lining will consist of reinforced concrete trapezoidal segments with an outer diameter of 6.3m, an inner diameter of 5.7m and a lengthof 1.4m.
“I was impressed by the Terratec machines when I attended the recent factory inspection and I am looking forward to great production records being set by the TBMs,” said Feriha Mert, Anatolian Rail Systems Manager for the IMM.
Tunnelling is expected to commence in early 2017 and be completed by mid-2019
The Terratec EPBM destined for the Phra Khanong cable tunnel project in Bangkok recently completed successful factory acceptance tests which were attended by representatives of Bangkok’s Metropolitan Electricity Authority (MEA) and Thai contractor Nawarat Patanakarn plc. Designed to accommodate a new high-voltage cable system, the new cable tunnel is the first of a series of planned tunnelling projects by the MEA that are being built to meet increased power demands in the Thai capital.
The project is situated in one of the busiest areas of downtown Bangkok and subject to tight alignment constraints. The machine will be launched from a 7m diameter shaft being constructed beneath the Ram Inthra -At Narong Expressway ramp with little working head room.
The first of two drives for the project will see the TBM head 495m south along Sukhumvit Road, at an upgrade angle of 1.2%, and terminate at a reception shaft located under the BTS Skytrain structure just short of On Nut Station. From there, the machine will be lifted and transported back to the launch shaftfor the second 293m long drive northwards under the Phra Khanong canal.
In order to negotiate the foundation piles of the expressway ramp , the TBM will be launched onto a sharp 32m radius curve on a 2% up-grade trajectory. The machine was designed with an X-type articulation system that provides a maximum articulation angle of 6.6 degrees to accommodate a minimum radius curve of 30m.
This type of extreme TBM articulation is popular in Japan, and Terratec teamed up with Japanese manufacturer JTSC to develop the design and export the technology to other countries.
The TBM back-up system is also tailored to accommodate the tight project requirements, including a mucking system that conveys spoil from the EPBM screw to a transfer pipe using compressed air.
The ground comprises fine sand and stiff clay, with an average overburden of 26m and a groundwater head of about 2 bar. The soft ground TBM cutterhead features an open spoke design with the addition of knife bits to assist break-in and break-out of the steel fibre reinforced concrete shaft eyes. Tapered precast concrete segments will be installed as the machine progresses, with shorter steel segments erected through the the sharp radius curve.
Machine operation will be assisted at all times by Terratecfield service staffto ensure optimum performance and project success. The tunnel is scheduled to go into operation at the end of 2017.