TERRATEC Breakthrough on Bangkok Purple Line
TERRATEC announced that one of its two 6.39-m OD Earth Pressure Balance (EPB) TBMs broke through Sam Yot Station on Contract 3 of the MRT Purple Line (Tao Poon–Rat Burana (Kanchanaphisek Road)) on June 18. A second machine’s parallel drive is expected to follow by the end of September 2026.
The two machines are driving twin tunnels (5.70-m ID) between Memorial Bridge and Phan Fa stations for the Mass Rapid Transit Authority of Thailand (MRTA). They were procured by the ITD-NWR MRT Joint Venture, the contractor delivering the tunnel and underground station works for Contract 3’s Phan Fa–Memorial Bridge section.
At Sam Yot Station, the twin Purple Line drives cross the existing MRT Blue Line Extension tunnel within the station box itself — the same crossing point where TERRATEC machines previously drove the Blue Line Extension’s own twin tunnels. With this breakthrough, TERRATEC TBMs have now completed three of the four tunnels driven through this single station, a section widely considered one of the most difficult and sophisticated on the Bangkok metro network given its location beneath the city’s Old Town and Chinatown districts. The crossing is engineered so that excavation has no influence on the operating Blue Line tunnel below, and the two Purple Line drives run independently, without crossing one another.
Contract 3 comprises 3.12 km of twin-bore tunnel serving two underground stations — Sam Yot and Memorial Bridge — supported by three intervention shafts along the route, and forms part of the wider 23.6 km MRT Purple Line extension connecting Tao Poon to Rat Burana via the Kanchanaphisek Ring Road. Further along the corridor, the Purple Line tunnels will also cross the alignment of the future Orange Line; because the Purple Line is being constructed first, the crossing presents no complication for the Orange Line’s later works. The drives will subsequently pass beneath the Chao Phraya River near Phra Pokklao Bridge, where riverbed cover above the tunnel crown exceeds one tunnel diameter (in excess of 6.5m).
Both machines are expected to complete their drives into Phan Fa Station by late 2026 or early 2027, extending the MRT network deeper into Bangkok’s historic core and strengthening connectivity between the Old Town, Chinatown and the wider Purple Line corridor between Tao Poon and Rat Burana. The full line is expected to enter operation in November 2030.
TERRATEC has a well-established regional base in Thailand, having supplied its first machine in the country 15 years ago for the MRT Blue Line Extension Project. With tailor-made robust TBM design, prompt onsite assistance, a readily available stock of TBM spares, and specialized support throughout the tunnelling operation, TERRATEC continues to be recognized as the country’s leading TBM supplier.
