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TBM arrives for Bangkok metro

The earth pressure balance TBM has arrived for Phase 1 of Bangkok’s new Orange metro line in Thailand.

Terratec has delivered a new tunnel boring machine for the first phase of the Mass Rapid Transit Authority (MRTA) Orange Line project, following successful factory acceptance testing.

The 6.39m diameter Terratec earth pressure balance machine (EPBM) will be deployed by contractor Italian-Thai Development PCL (ITD) on one of three underground civil works contracts for the first 23km-long (East) phase of the project, which comprises 11.38km of twin single-track tunnel alignment and 9km of elevated track running from the central Thailand Cultural Centre station to Suwinthawong station in the east.

The contract was awarded to ITD in May 2017, and includes over 6km of TBM driven tunnel and three underground stations, extending from Hua Mak to Khlong Ban Ma.

Designed to tackle Bangkok’s complex and variable soft ground geology, the TBM will bore through soft and medium to stiff and very stiff clays, with lenses of dense sand and the potential for high pressure groundwater inflows.

The TBM’s soft ground cutterhead features a spoke style design with a 43% opening ratio and the addition of back-loading knife bits to assist break-in and break-out of the concrete station shaft eyes.

In addition, the machine is fitted with an active bentonite face support injection system and double gated screw, to ensure face stability and mitigate ground settlement during excavation within areas of flowing sands and high groundwater pressure.

ITD project manager Sanya Thirakajornwong said: “Despite the complex works that lie ahead of us on this project, we are very confident in the design of the machine and that it will perform well in the expected conditions,”

Tunnel excavation is due to begin in December.

As the machine progresses along the alignment, it will install a precast concrete segmental lining consisting of five x 1200mm wide universal style segments plus key, with an internal diameter of 5.7m.

When complete in 2023, the 35.4km Orange Line with 26.2km aligned underground with 23 underground stations and another 9km and seven stations on elevated structures.

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