India’s first undersea rail tunnel excavation for the Mumbai–Ahmedabad high-speed rail project is underway. Multiple outlets report that on Saturday a second Tunnel Boring Machine (TBM) started tunnelling from Sawli (Ghansoli) toward Vikhroli, following an earlier start by the first TBM from Vikhroli toward the Bandra Kurla Complex (BKC) in early July. The works cover a long underground alignment between BKC and Sawli, with sources describing the most complex portion as part of a roughly 21-km underground section. Within that, the undersea stretch beneath Thane Creek is expected to run about 7 km. One report also describes the second TBM as a “Mixshield” type with a large cutterhead and weight, designed for Mumbai’s difficult ground conditions while limiting settlement and surface disruption.
Sources also state that launching the TBM required a deep shaft at Sawli for lowering and assembly. The project includes safety and monitoring measures, such as real-time gas monitoring, fire protection systems, emergency refuge chambers, and networks of sensors for ground movement and vibration. Officials say the tunnel is being built to be waterproof, using sealing systems intended to prevent water ingress.
