Terratec has delivered another new 6.39m diameter EPBM for the construction of the Bangkok Metro Purple Line (C3).

The first EPBM was delivered in December last year.

The two machines will construct a 3.12km tunnel, linking Phan Fa Station to Memorial Bridge Station through two metro stations.

The project faces several challenges, particularly driving the TBMs through the historic area of the old Bangkok capital, which features landmarks such as the Grand Place and ancient temples.

At the interchange station at Sam Yod, linking the Purple Line with the existing Blue Line MRT, the new line will pass beneath the operational Blue Line tunnels.

The TBMs will also tunnel under the Chao Phraya River for a 150m stretch.

The geological conditions along the tunnel routes will include sand layers such as soft clay, stiff clay, dense clayey and silty sand. To address these conditions, the EPBMs’ soft ground cutterheads are fitted with a flat spoke type with copy cutters.

Throughout the construction process, traditionally reinforced, 275mm thick by 1400m wide, Universal reinforced concrete segments (5 + 1) will be installed as the TBM advances. Muck removal, segments, and the supply of consumables will be transported by rail-bound equipment using battery locomotives.

Terratec TBMs are equipped with the Enzan laser guidance system, which provides remote monitoring of the entire tunnelling system, offering precise control over TBM operations.

The Bangkok Metro Purple Line, stretching 23.63km and serving north-west Bangkok from Tao Poon to Klong Bang Phai in Nonthaburi Province, is the city’s fifth rapid transit line. Construction of the southern extension, comprising a 14.3km underground section, a 9.3km elevated section and 17 stations, commenced in August 2022. The line is expected to commence service in 2027.