Challenging drive ahead for Bangkok Metro 02 Aug 2018

Complex and variable soft ground conditions, ranging from soft and medium to stiff and very stiff clays, with lenses of dense sand and the potential for high pressure groundwater inflows, await launch and operation of a 6.39m diameter EPBM from Terratec on the Orange Line of the Bangkok Metro. Procured by contractor Italian-Thai, the TBM will work on one of three underground civil works contracts for the first 23km-long east phase of the Orange Line, which comprises 11.38km of twin single-track tunnel alignment under the city centre of Bangkok.

Contract E3 was awarded to Ital-Thai in May 2017 and totals more than 6km of TBM driven tunnel and three underground stations. The Terratec TBM has been designed to tackle the challenging soft ground geology under Bangkok in several ways.

Complex drives lie ahead for the 6.39m diameter EPBM

The soft ground cutterhead of the TBM features a spoke style design with a 43% opening ratio and 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.

“Despite the complex works that lie ahead of us on this project, we are confident in the design of the machine and that it will perform well in the expected conditions,” said Sanya Thirakajornwong, ITD Project Manager. “The TBM will arrive on site at the end of July, with tunnel excavation due to begin in December, proving that TBM production has been on schedule and that the delivery was well-prepared. It will also be a great pleasure to work with Terratec field service support staff once again, allowing us to meet project completion effectively and efficiently” said Sanya Thirakajornwong, Project Manager for Ital-Thai.

Excavation due to begin December 2018

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. These are being produced by Ital-Thai at the same factory used for segment manufacture during its MRT Blue Line underground works contract five years ago, which also employed a Terratec TBM.

Bangkok new Orange Line will eventually total about 35.4km with 26.2km aligned underground with 23 underground stations and another 9km and seven stations on elevated structures. The route starts underground at Taling Chan railway station, west of the city, passes under the Chao Phraya River near Somdet Phra Pin Klao Bridge, and connects to the depot of the Mass Rapid Transit Authority of Thailand (MRTA), which is located at the current MRTA Office Building. It then continues along the Rama IX road, turns left into Ram Khamhaeng Road, passes beneath the Lam Sari intersection and transitions to the elevated section from the Khlong Ban Ma Station, terminating at Suwinthawong Station near the Ram Khamhaeng-Suwinthawong junction.

Shipment of the 6.39m EPBM for delivery to Bangkok is underway following successful factory acceptance testing in July. Once on site and launched, TBM operation will be assisted at all times by Terratec field service staff, providing quality after sales support to ensure optimum performance and successful project completion.

When complete in 2023, the Orange Line will provide a vital transportation link from Bangkok city centre to districts in the east, reducing traffic congestion and paving the way for improved accessibility, economic growth and new residential and commercial opportunities along the alignment.