The National High Speed Rail Corporation Limited (NHSRCL) has announced that the second Tunnel Boring Machine (TBM) has begun excavation work for the Mumbai-Ahmedabad bullet train project. The TBM started its journey from Sawli (Ghansoli) towards Vikhroli in Maharashtra, marking a significant milestone in the project’s progress.
The Mumbai-Ahmedabad High Speed Rail (MAHSR) corridor includes a 21-km-long underground tunnel between Sawli (Ghansoli) and Bandra Kurla Complex (BKC) in Mumbai. A 7-km section of this tunnel will pass beneath Thane Creek, making it India’s first undersea tunnel for a railway corridor. The tunnel is being constructed using Tunnel Boring Machines (TBMs), with the first TBM commencing its 6-km drive from Vikhroli towards BKC on July 5, 2026.
The second TBM is among the largest machines ever deployed for railway tunnel construction in India, boasting a 13.6-metre-diameter cutterhead and weighing around 3,200 tonnes. The machine is 96 metres long and features several key components, including a cutter wheel/head, main bearing, jaw crusher, erector, main shield, tail shield, and four specialized gantries that support tunnelling operations.
The TBM is configured as a Mixshield type, semi-automatic, slurry-based machine, utilizing a pressurized liquid bentonite slurry circuit to stabilize the tunnel face during excavation. This technology provides a highly reliable and proven method for driving through complex and challenging geological conditions.
The NHSRCL has designed the tunnel section excavated using TBMs as a fully waterproof structure, with continuous real-time monitoring systems in place to ensure structural performance, groundwater behavior, and overall construction safety. To prevent water ingress, the tunnel lining is protected using double-layer Ethylene Propylene Diene Monomer (EPDM) gaskets combined with hydrophilic seals, ensuring long-term structural durability and safety.
