With seven TBMs currently at work on major underground projects in Thailand, TERRATEC marks its latest milestone on Bangkok’s Orange Line metro project.

Having delivered seven TBMs to Thai underground works projects in the last three years (representing every machine currently being operated in the country), TERRATEC continues to make great progress, with a number of milestones being celebrated over recent months. In Bangkok, solid results are already being seen on the first phase of tunnelling for the Orange Line metro project, as well as on a number of tight radius Earth Pressure Balance Machine (EPBM) drives for drainage and cable tunnel projects across the capital. Meanwhile, in the northern province of Chiang Mai, two TERRATEC hard rock Double Shields are achieving steady progress on the 25km-long Phase 2 tunnelling works for the Royal Irrigation Department’s Mae Tang-Mae Ngad water diversion project.

In January, TERRATEC joined workers and officials in celebrating the launch of the 6.39m diameter S70 EPB machine by contractor Italian-Thai Development PCL (ITD) on one of three underground civil works contracts for the first 23km-long (East) phase of the Mass Rapid Transit Authority of Thailand’s (MRTA) Orange Line Project.

Contract E3, which was awarded to ITD in May 2017, totals over 6km of TBM driven tunnel and three underground stations, extending from Hua Mak to Khlong Ban Ma. The S70 machine began mining westwards from the Khlong Ban Ma station box on January 12, 2019, and quickly got up to speed following its initial drive. By late-March, the TBM had already mined 400m – achieving progress rates of up to 18 rings per day – and had undertaken its first intermediate breakthrough into a ventilation shaft (IVS 17) where it was undergoing a cutterhead inspection. The TERRATEC S70 TBM was designed to tackle the variable soft ground geology of the city – which ranges from soft and medium to stiff and very stiff clays, with lenses of dense sand and the potential for high pressure groundwater inflows – as well as the need to mine through numerous diaphragm wall shafts and, potentially, concrete piles. “We are in a very congested area of the city, tunnelling underneath a busy highway that has a flyover directly above it and buildings with deep foundations on both sides,” says Prakin Arunotong, Senior Vice President of ITD’s MRT Business Unit. “So we need to carefully protect those structures during tunnelling and station construction.”

In order to handle these challenging conditions, the TBM’s soft ground cutterhead features a spoke style and the addition of back-loading knife bits to assist break-in and break-out of the shafts. In addition, the machine is fitted with an active bentonite face support injection system and double gated screw, to ensure face stability and mitigate settlement during excavation in areas of flowing sands and high groundwater pressure.

As the machine progresses along the alignment, it is installing 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 ITD 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.

In total, TBM tunnelling operations for ITD’s Orange Line (East) contract are expected to last approximately two years and are being assisted at all times by TERRATEC’s highly-experienced Field Service staff – who’s quality after sales support service has created very loyal client-base in Thailand – to ensure optimum performance and successful project completion.

“We have worked closely with TERRATEC since 2012, when we won our MRT Blue Line extension contract,” says Arunotong. “TERRATEC has a very similar working style to our own and because of this we consider our partnership with them as more of an ‘Alliance’ than that of the traditional contractor-TBM manufacturer relationship.”

Bangkok’s 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. When complete, in 2023, the Orange Line will provide a vital transportation link from Bangkok’s 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.

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