Metro Orange Line progresses in Bangkok 18 Apr 2019

After being launched in January 2019 from the Khlong Ban Ma station box, a Terratec 6.39m diameter EPBM is making good progress on one of three underground civil works contracts for the first 23km-long east phase of the Orange Line for the Thailand capital city Mass Rapid Transit Authority for contractor Italian-Thai Development plc (ITD). By late March the TBM had excavated 400m, achieving progress rates of up to 18 rings/day.

Terratec 6.39m diameter for Orange Metro Line

Contract E3 was awarded to ITD in May 2017 and totals more than 6km of TBM driven tunnel and three underground stations, extending from Hua Mak to Khlong Ban Ma.

The Terratec 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, plus the need to excavate 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, so we need to carefully protect those structures during tunnelling and station construction,” said Prakin Arunotong, Senior Vice President of ITD MRT Business Unit.

In order to handle these challenging conditions, the TBM 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, it will install a precast concrete segmental lining consisting of five x 1.2m wide universal style segments plus key, with an internal diameter of 5.7m. The segments 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.

EPBM launched westwards from Khlong Ban Ma

In total, TBM tunnelling operations for the ITD Orange Line East contract are expected to last approximately two years and are being assisted by Terratec field service staff. The Bangkok Metro 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 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.

Terratec has now delivered seven TBMs to Thai underground works projects in the last three years, representing every type of machine currently being operated in the country. In addition to progress on the Orange Metro Line in Bangkok, results are being seen on a number of tight radius 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 Mae Tang-Mae Ngad water diversion project.