Two TERRATEC EPB TBMs complete over 5km of challenging urban tunnelling beneath Bangkok to advance the city’s major water transmission upgrade.
TERRATEC earth pressure balance TBMs have achieved final breakthrough on Contract G-TN-9B of Bangkok’s 9th Water Supply Improvement Project, completing excavation works for the 9.1km water transmission tunnel.
TERRATEC has announced the successful completion of tunnelling works on Contract G-TN-9B of Bangkok’s 9th Water Supply Improvement Project, following final breakthrough of two EPB tunnel boring machines in December 2025.
The two machines were launched from Shaft 9B-1, completing drives of 2,250m and 3,120m respectively, with breakthroughs at Shaft 9A-5 and Shaft 9B-3. Together with the third EPB TBM previously completed on the contract, all excavation works for the 9.1km scheme have now been successfully finished for Italianthai-Nawarat JV.
The tunnel alignment passes beneath heavily trafficked urban corridors and incorporates multiple horizontal curves to avoid flyover bridge foundations. Excavation was carried out at depths of approximately 27m to 34m within silty and clayey sand strata typical of the Bangkok basin, requiring precise control of face pressure and ground conditions.
Despite complex launching arrangements and restricted shaft environments, steady production was maintained throughout the drives, with average advance rates of 10–12 rings per day and a peak monthly advance of 429.7m. Across the two drives, more than 4,500 segmental rings were installed and nearly 90,000m³ of material excavated. Tunnelling was completed safely and without major incident.
Steel liner installation is currently underway and is expected to be finalised approximately four months after breakthrough. Upon commissioning, the new transmission tunnel will support expanded capacity at the Mahasawat water treatment plant and enhance Bangkok’s long-term water supply resilience.
TERRATEC has a well-established regional base in Thailand, having sold its first machine in the country 15 years ago for the Metropolitan Rapid Transit (MRT) Blue Line Extension Project. With outstanding tailor-made robust TBM design, prompt onsite assistance, a readily available stock of TBM spares, and specialised support throughout the tunnelling operation, TERRATEC has become the country’s leading TBM supplier.
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