Terratec TBMs get ready for Bangkok Metro Purple Line project

In December 2023, Terratec celebrated the successful factory acceptance test of a new 6.39-m-diameter earth pressure balance tunnel boring machine (EPB TBM) which will be deployed for the construction of the Bangkok Metro Purple Line (C3) in Thailand.

The event was attended by representatives from the Mass Rapid Transit Authority of Thailand and contractor ITD-NWR MRT Joint Venture. The second factory acceptance test for another EPB TBM is scheduled to take place in April 2024.

The Bangkok Metro Purple Line, spanning a length of 23.63 km and serving the northwestern area of Bangkok from Tao Poon to Khlong Bang Phai in Nonthaburi province, is the fifth rapid transit line in the city. Its southern extension, which comprises a 14.3 km underground section and a 9.3 km elevated section, commenced construction in August 2022 and includes a total of 17 stations.

The two Terratec EPB TBMs will be utilised to construct a total tunnel length of 3.12 km, connecting Phan Fa Station to Memorial Bridge Station across two metro stations.  

The project encounters several challenges, said Terratec, particularly in navigating the TBMs through the historic area of the old Bangkok capital, which includes landmarks like the Grand Palace and old temple. Another significant aspect is the interchange station at Sam Yod, connecting the Purple Line with the existing Blue Line MRT.

The Purple Line will ingeniously pass beneath the operational Blue Line tunnels. Additionally, the TBMs will undergo an impressive feat by driving under the Chao Phraya River for a stretch of 150 m. The construction process necessitates meticulous planning and management to ensure minimal disruptions to the surrounding infrastructure and environment.

According to Terratec, the geological conditions along the tunnel alignments will encompass soft clay, stiff clay, dense clayey and silty sand. To accommodate these conditions, the TBM’s soft ground cutterhead is equipped with a flat spoke type with copy cutters.

During the construction process, traditionally reinforced, 275 mm thick by 1,400 m wide, Universal reinforced concrete segments (5 + 1) will be installed as the machine progresses. Muck removal, segment transport, and the supply of consumables will be facilitated by rail-bound equipment using battery locomotives.

Terratec TBMs feature the Enzan laser guidance system, which allows for remote access to the complete tunnelling system, thus ensuring accurate control over the TBM operations. With this Enzan system, precise navigation of the tunnels is guaranteed to improve the efficiency and effectiveness of tunnelling projects.