Tight alignment facing EPBM cable drive 03 May 2018

At the end of April 2018, the successful factory acceptance test was celebrated for a new 4.27m diameter Terratec EPBM destined for the Chidlom Cable Tunnel Project in Bangkok, Thailand.

Representatives celebrate factory acceptance

The new project will accommodate a high-voltage cable system, and is one of a series of tunnelling projects being undertaken by the MEA to meet increased power demands in the Thai capital.

Running from the Central Embassy mall and the MEA Chidlom Electrical Facilities southwards to Lumphini Park, the project is located in one of the busiest and most built up areas of downtown Bangkok, and is subject to tight alignment constraints including the need to carefully navigate the foundations of the Chit Lom BTS Skytrain Station. To achieve this, the Terratec EPBM has been designed with an extreme X-type articulation system, which can accommodate very tight radius curves.

“We have worked closely with Terratec on a number of projects in the past and were keen to work with them again,” said Supak Khunviriya, Project Manager for ITD. “Terratec has past experience of similar projects with tight radius curves in Bangkok and the TBM has been designed to achieve a high level of performance in difficult circumstances.”

The soft ground cutterhead features an open spoke design with the addition of knife bits to assist break-in and break-out of the concrete shaft eyes. Universal tapered precast concrete segments will typically be installed as the machine progresses, with shorter steel segments utilised during the course of the sharp radius curves.

The EPBM will face tight alignment

Geological conditions along the 1.35km tunnel alignment consist of stiff to very stiff clay with lenses of sand and a groundwater head of about 2 bars.

Due to heavy traffic and the physical limitations of this built up area – which includes numerous high-rise buildings and the skytrain viaduct – logistics during the launch and operation of the TBM will be extremely challenging, especially during the transportation and delivery of oversize TBM parts for assembly at site. Terratec highly-experienced Field Service staff have therefore been working closely with ITD from day one in order to ensure every aspect is planned in advance.

“We have great faith in the Terratec staff, who will assist us throughout the tunnel construction stage,” said Khunviriya. “There has been a close collaboration and exchange of information with Terratec since the tender stage.”

Following the factory acceptance test which was attended by representatives of Bangkok’s Metropolitan Electricity Authority (MEA) and contractor Italian-Thai Development PCL (ITD), the machine will now be shipped to Thailand and is expected to arrive in early-May. It will then be transported to the project site and lowered down the main shaft in a carefully-planned operation that will take place in a single night.