Construction of the underground section of India’s first high-speed rail corridor is set to enter a new phase as the first Tunnel Boring Machine (TBM) prepares to begin excavation beneath Mumbai. The development marks a significant engineering milestone for the Mumbai–Ahmedabad High-Speed Rail project, advancing one of the country’s most technically demanding transport infrastructure initiatives while strengthening capabilities in complex urban tunnelling.
The launch of the first TBM from the Vikhroli worksite will initiate excavation towards Bandra Kurla Complex (BKC), where the underground alignment forms part of a 21-kilometre tunnel connecting Mumbai with Shil Phata. The section includes India’s first undersea rail tunnel beneath Thane Creek and has been designed to navigate one of the nation’s most densely built metropolitan regions with minimal disruption to surface transport and surrounding communities. The Mumbai Bullet Train Tunnel is being constructed using a combination of advanced tunnelling technologies. While a portion of the underground alignment has already been completed through the New Austrian Tunnelling Method (NATM), the remaining sections are being excavated using large Tunnel Boring Machines capable of operating through varying geological formations. The first machine will construct nearly six kilometres of tunnel, with a second TBM expected to begin operations later this month, allowing simultaneous excavation from multiple locations. Engineers involved in the project indicate that the machine has been designed to maintain operations throughout the monsoon, supported by continuous monitoring systems that assess ground movement and structural stability. Given the tunnel’s passage beneath urban neighbourhoods, transport corridors and the Mithi River, construction teams are employing advanced instrumentation to monitor settlement, vibration and ground behaviour in real time, helping safeguard nearby infrastructure.
Urban infrastructure specialists view the Mumbai Bullet Train Tunnel as a landmark in India’s evolving underground construction capabilities. The deployment of one of the country’s largest rail tunnel boring machines reflects a growing shift towards mechanised excavation methods that improve construction precision, reduce environmental disturbance and enhance worker safety in densely populated cities. Beyond the engineering achievement, the underground corridor is expected to demonstrate how major transport investments can coexist with complex urban environments. By routing high-speed rail below ground, the project seeks to minimise land acquisition, preserve existing development and reduce disruption to economic activity during construction. Experts also note that experience gained from the Mumbai section could influence future underground transport projects, including metro systems and planned high-speed rail corridors in other metropolitan regions.
Lessons in tunnel design, groundwater management, structural monitoring and construction sequencing are likely to strengthen India’s institutional capacity for delivering resilient transport infrastructure. As excavation progresses, attention will shift towards integrating the underground tunnel with track systems, electrification and operational infrastructure required for commercial services. The successful execution of this section is expected to remain critical to the timely completion of the Mumbai–Ahmedabad High-Speed Rail corridor and to India’s broader ambitions of building a modern, sustainable and climate-resilient intercity transport network.
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