Construction of India’s first undersea railway tunnel has entered a significant new phase as tunnel boring operations advance beneath Thane Creek for the Mumbai Ahmedabad Bullet Train corridor. The deployment of a second tunnel boring machine (TBM) marks a major engineering milestone for the country’s first high-speed rail project and reflects continued progress on one of its most technically demanding sections.
The newly launched TBM will excavate a section of the tunnel connecting the Ghansoli area with Vikhroli in Mumbai. This underground alignment forms part of the 21-kilometre tunnel planned between Bandra-Kurla Complex (BKC) and Ghansoli, with approximately seven kilometres passing beneath Thane Creek. Once completed, it will become India’s first railway tunnel constructed beneath a marine environment. The Mumbai Ahmedabad Bullet Train tunnel combines multiple construction techniques to address varying geological conditions. While a section has already been completed using the New Austrian Tunnelling Method (NATM), the remaining underground stretch is being excavated using large-diameter tunnel boring machines designed to operate safely beneath densely populated urban areas and sensitive ecological zones.
Engineers describe the TBM as one of the largest deployed for railway infrastructure in India. The machine is capable of excavating wide-diameter tunnels while simultaneously installing precast concrete lining segments that provide structural stability during construction. To facilitate the launch, project teams developed a deep access shaft allowing the machine’s components to be assembled below ground before excavation commenced. Infrastructure specialists note that tunnel boring technology offers significant advantages in complex urban environments by reducing surface disruption, limiting noise and vibration, and minimising impacts on existing transport networks. Such engineering methods are increasingly used in metro systems and high-speed rail projects worldwide where underground alignments help preserve land and avoid densely developed areas.
The undersea tunnel is regarded as one of the defining engineering features of the Mumbai Ahmedabad Bullet Train project. Beyond reducing land acquisition requirements in highly urbanised locations, the tunnel is expected to improve route efficiency while demonstrating India’s growing capability to deliver technically advanced transport infrastructure. Urban planners also highlight the broader significance of the project for regional mobility. High-speed rail has the potential to reshape travel patterns between Maharashtra and Gujarat, supporting economic integration, reducing dependence on road transport and encouraging lower-carbon intercity mobility when integrated with local public transport systems. Although sections of the project have recently faced weather-related construction challenges and ongoing legal proceedings related to land acquisition, tunnelling progress indicates that work continues across multiple construction packages. As excavation advances beneath Thane Creek, the project moves closer to completing one of its most complex structural components, bringing India’s first high-speed rail corridor another step towards operational readiness.
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