3 min readNew DelhiUpdated: Feb 3, 2026 09:12 PM IST
India’s ambitious Bullet Train project, the Mumbai-Ahmedabad High Speed Rail, achieved the breakthrough of its second mountain tunnel — the third tunnel overall — in Palghar, Maharashtra, on Friday. The tunnel is 454 m long and 14.4 m wide and is almost 47% complete.
Last month, the Railways achieved the tunnel breakthrough for the Bullet Train project’s first mountain tunnel, MT-5, located between Virar and Boisar stations in Palghar.
A tunnel breakthrough is the point or moment when a tunnel being excavated from both ends finally connects at the centre and creates a clear passage through the mountain. The second mountain tunnel, MT-6, has been excavated from both sides using a cutting-edge drill and blast method, also called the New Austrian Tunneling Method (NATM).
Railways officials said the excavation work was completed in 12 months. NATM is used where the geological condition is irregular, requiring different strategies as the work progresses and the tunnel boring machines (TBM) are not suitable.
Of the 508-km length of the bullet train project, tunnels comprise 27.4 km. Of these, 21 km make up the underground tunnels while the total length of surface tunnels is 6.4 km. Surface tunnels include eight mountain tunnels, seven of which are in Maharashtra’s Palghar district (6.05 km) while one is in Gujarat (350 m).
Officials said the project’s longest river bridge over the Vaitarna river has reached pier level and the foundation level work on the rivers Ulhas and Jagani has been completed.
The first breakthrough in the project was of a 4.88-km underground tunnel between Ghansoli and Shilphata, achieved in September 2025. This is part of a bigger, 21-km tunnel being constructed between the Bandra-Kurla Complex (BKC) and Shilphata in Maharashtra. This stretch also includes a 7-km long undersea section beneath the Thane Creek.
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At present, work on all the tunnels is ongoing. In Maharashtra, mountain tunnel number 1 (MT-1), which is 820 m long, has achieved 16% physical progress while the 228-m MT-2 is currently under preparatory works. MT-3, measuring 1.4 km in length, has achieved 41% completion while the 1.26 km MT-4 is 32% complete. Similarly, MT-5 has achieved 57% progress while the 417 m MT-7 is 29% complete.
The Centre announced seven more high-speed rail corridors as “Growth-Connectors” in the Union Budget 2026-27. These are Mumbai–Pune, Pune-Hyderabad, Hyderabad-Bengaluru, Hyderabad-Chennai, Chennai-Bengaluru, Delhi-Varanasi and Varanasi-Siliguri high-speed rail corridors. These corridors together span 4,000 km and will require Rs 16 lakh crore expenditure in construction.
In the Mumbai-Ahmedabad high-speed rail corridor, around 334 km of viaducts, 17 river bridges, and 12 major crossings over national highways, railways, and other infrastructure have been completed. Laying of tracks and electrification is underway. The first section from Surat to Bilimora in Gujarat is scheduled to be operational by August 15, 2027. The entire 508-km project is expected to be completed by December 2029.
The cost of the project has almost doubled. At the beginning of the project, it was estimated that the project would require an investment of Rs 1.08 lakh crore. This estimate has now escalated to Rs 1.98 lakh crore.
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