Mumbai, July 21 -- The second tunnel boring machine (TBM) has begun excavation of the 7-km undersea tunnel beneath Thane Creek for the Mumbai-Ahmedabad Bullet Train Project, marking another milestone in the construction of India's first undersea rail tunnel.
The TBM commenced its drive from Sawli (Ghansoli) towards Vikhroli as part of the project's 21-km underground section. Of this, 16 km between Sawli and Bandra Kurla Complex (BKC) will be excavated using TBMs, while the remaining 5 km has already been completed using the New Austrian Tunnelling Method (NATM). The first TBM began tunnelling from Vikhroli towards BKC on 5 July 2026.
The slurry-based Mixshield TBM features a 13.6-m-diameter cutterhead, weighs 3,200 tonnes and is 96 m long, making it among the largest machines deployed for rail tunnelling in India. The machine is equipped with a semi-continuous advance system that enables simultaneous excavation and tunnel lining installation to improve construction efficiency.
A 39-m-deep launch shaft was constructed at Sawli to deploy the TBM, which was assembled underground after being lowered in sections because of space constraints.
The project incorporates real-time monitoring systems to track ground movement, structural behaviour and gas levels during excavation. The tunnel lining is being designed as a fully waterproof structure using double-layer EPDM gaskets and hydrophilic seals to prevent water ingress and enhance long-term durability.
Published by HT Digital Content Services with permission from Construction World.