The machine is a 4.27m-diameter Terratec EPBM, equipped with an X-type articulation system to meet the tight curve requirements of the tunnel alignment, which must follow public road easements. The machine, which is capable of excavating a minimum radius curve of 48m, will be used to conduct three tunnel drives (of 1,128m, 875m and 795m in length), at a maximum depth of 31m, each beginning or ending with a tight curve.

Geological conditions along the tunnel alignments will consist of mixed faces of very stiff to hard or silty clay and very dense to very fine sand. The TBM’s soft ground cutterhead features a spoke design with a 70% opening ratio and the addition of knife bits to assist break-in and break-out of the concrete shaft eyes.

Traditionally reinforced, 250mm thick by 1200m wide, Universal tapered precast concrete segments (4 + key) will be installed as the machine progresses and muck removal, segment transport and machine supply will be via rail bound equipment.

Designed to accommodate a new high-voltage cable system, the Klong Daan Cable Tunnel Project is one of a series of tunnelling projects being undertaken by the MEA, which are being built to meet increased power demands in the Thai capital.

Following the successful factory acceptance test, the machine will be now shipped to Thailand and is expected to arrive in mid-2019. The TBM will then be transported to the project site where it will be launched on its initial 1,128m-long drive.