TBM launched for the Bangkok Orange Line

The contractor is Italian-Thai Development PCL (ITD), which is carrying out one of three underground civil works contracts. The contract E3, which was awarded to ITD in May 2017, includes 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 12th January 2019, and then speeded up following its initial drive. By late-March, the TBM has already mined 400m, achieving progress rates of up to 18 rings per day and has undertaken its first intermediate breakthrough into a ventilation shaft (IVS 17), where it was undergoing a cutter head inspection.

“We are working in a very congested area, 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.”

To face such challenges, the TBM’s soft ground cutterhead has been equipped with a 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. Segments are being produced by ITD at the same factory that was used for the MRT Blue Line five years ago.

TBM tunnelling operations for ITD’s east contract are expected to last approximately two years and are being assisted by Terratec’s field service staff. 

Bangkok’s new Orange Line will be 35.4km long with 26.2km aligned underground including 23 underground stations. Once complete in 2023, the Orange Line will provide a transportation link from Bangkok’s city centre to districts in the east.