Construction of the underground section of the Mumbai Ahmedabad Bullet Train corridor has entered another significant phase with excavation progressing beneath Thane Creek through the deployment of an additional tunnel boring machine (TBM). The latest engineering milestone advances work on India’s first undersea railway tunnel, a project expected to redefine high-speed rail connectivity while showcasing increasingly sophisticated underground construction capabilities.
The newly commissioned TBM has begun excavating the alignment between the Ghansoli area and Vikhroli in Mumbai, contributing to the completion of the 21-kilometre underground section connecting Bandra-Kurla Complex (BKC) with Ghansoli. Around seven kilometres of this alignment will pass beneath Thane Creek, making it the country’s first rail tunnel constructed below a marine environment. Infrastructure experts consider the underground section one of the most technically challenging components of the Mumbai Ahmedabad Bullet Train project. The corridor traverses densely populated urban districts, existing transport infrastructure and environmentally sensitive coastal ecosystems, requiring precision engineering that minimises disruption at the surface while ensuring long-term structural resilience.
Officials associated with the project indicate that different tunnelling techniques are being employed to match local geological conditions. While part of the underground alignment has already been completed using the New Austrian Tunnelling Method (NATM), the remaining stretch is being excavated using large-diameter tunnel boring machines capable of simultaneously cutting through varying soil formations and installing reinforced tunnel lining segments. The newly deployed machine ranks among the largest tunnel boring systems used for railway infrastructure in India. Its scale allows excavation of a wide tunnel profile designed to accommodate high-speed rail operations while maintaining stringent engineering and safety standards. To facilitate assembly, engineers first developed a deep launch shaft, enabling the machine to be lowered underground in multiple components before excavation commenced. Urban transport planners note that underground alignments reduce the need for extensive land acquisition in heavily developed metropolitan areas and minimise impacts on surrounding communities during construction. They also help preserve existing road networks, utilities and commercial districts while improving the long-term efficiency of regional transport corridors.
The Mumbai Ahmedabad Bullet Train remains India’s flagship high-speed rail initiative, intended to strengthen economic integration between Maharashtra and Gujarat by reducing travel time and encouraging a shift towards lower-emission public transport. As construction progresses across multiple civil packages, the project continues to demonstrate how advanced engineering technologies can support large-scale mobility infrastructure within complex urban landscapes. With excavation now advancing simultaneously from multiple points, attention will increasingly shift towards completing the underground tunnel network before track installation and systems integration begin. Successful delivery of this engineering segment will represent an important milestone in India’s evolving high-speed rail programme and provide valuable experience for future underground transport projects across rapidly growing metropolitan regions.
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