Contractor Italian-Thai Development PCL (ITD) has completed tunnelling on the Rama III Tunnel Project for the Bangkok’s Metropolitan Electricity Authority, in Thailand. The tunnel was completed using a TERRATEC 4.27m diameter Earth EPBM which successfully holed through in early April 2022 in downtown Bangkok.
The Rama III is a new high-voltage cable tunnel which is one of a series of tunnelling projects being undertaken by Bangkok’s Metropolitan Electricity Authority (MEA), which are being built to meet increased power demands in the Thai capital.
This project is subject to several constraining factors including tight alignment constraints and navigating the foundations of the overhead bridges along the alignment. This was achieved thanks to the X-type articulation system incorporated into the design, which can accommodate the very tight radius curves required by the project of approximately 85m. The TERRATEC 4.27m diameter’s soft ground cutterhead features an open spoke design to ensure good material flow and the addition of knife bits to assist break-in and break-out of the concrete shaft eyes.
Two types of segment were installed, universal tapered precast concrete segments, 1200mm long (installed as the machine normally progresses), and shorter steel segments, 600mm long (utilised during the course of the sharp radius curves).
Tunnelling operations were closely observed throughout the project via a settlement monitoring programme that demonstrated minimal impact on the existing above-ground structures.
Geological conditions along the 3.5km Rama III tunnel alignment consist of stiff to very stiff clay with lenses of sand and a groundwater head of about 2 bars.
The project is located close to the Chao Phraya River with heavy traffic and the physical limitations of this built-up area – which includes numerous high-rise buildings and the foundation of the overhead bridge. Logistics during the launch and operation of the TBM were extremely challenging especially during the transportation and delivery of oversize TBM parts for assembly on site.