Why the railways’ tunnel breakthrough matters for Mumbai-Ahmedabad bullet train project

Union Minister of Railways Ashwini Vaishnaw described it as a major milestone: “A crucial 4.8-kilometre section of the tunnel was successfully completed today. The Japanese team also reviewed it and expressed satisfaction. The 320 km bridge portion of the project has been completed. This project will reduce the travel time from Mumbai to Ahmedabad to 2 hours and 7 minutes.”

He added that the bullet train will have reasonable fares and cater to the middle class.

What is the Mumbai-Ahmedabad bullet train project?

The project covers 508 km across Gujarat (348 km), Maharashtra (156 km) and Dadra and Nagar Haveli (4 km). It involves high-level engineering and technical capabilities to construct India’s first high-speed corridor.

Bullet train route map.

Work began in December 2017. However, the August 2022 deadline had to be advanced, as protests and legal issues arising from land acquisition from farmers led to delays.

With 12 stations on the route and an operational speed of 320 km per hour, the high-speed rail is among the flagship projects signed between India and Japan. It will cost more than Rs 1 lakh crore, with 80% of the funding coming from Japan.

Vaishnaw said, “The first section of the Bullet Train project from Surat to Bilimora will become operational in 2027. After that, the train will be taken to Thane in 2028 and to Mumbai in 2029. The project will have a multiplier effect on the economy, as it happened in Japan. The services of the train have been planned in such a way that during the peak hour, a bullet train will be available every half an hour. After the complete network becomes stable, the high-speed train service will be available every 10 minutes.”

Why is the tunnel breakthrough important?

Of the 21 km-long tunnel, the 4.88 km section has been excavated using the New Austrian Tunnelling Method (NATM), while the remaining will be excavated using Tunnel Boring Machines. NATM is used where the rock formation is not uniform, requiring controlled and small-scale excavations and detonations.

A bridge under construction for the Mumbai-Ahmedabad bullet train project. (Ministry of Railways)

The longer tunnel also includes a 7-km-long undersea section beneath the Thane Creek. Additionally, 320 km of viaduct construction has been completed.

Officials from the National High-Speed Rail Corporation Limited (NHSRCL), the implementing agency, said the NATM tunnelling for this stretch was done in three phases. The first breakthrough of the 2.7 km tunnel section was achieved on July 9. The latest breakthrough is its continuation, from the Savali shaft to the Tunnel Portal at Shillphata. The tunnel will connect to the viaduct portion of the project at Shillphata.

“The breakthrough essentially means the completion of the excavation works in complex geological conditions and validates the successful application of engineering works, including drilling and blasting, survey works, support systems, etc. It allows the project to move into the final stages, such as waterproofing, lining, finishing, and equipment installation,” said a senior official of NHSRCL.

Currently, according to NHSRCL, 398 km of pier work has been completed. Further, 17 river bridges and nine steel bridges have been built. More than 4 lakh noise barriers have been installed along over 200 km, and around ⁠206 km of track bed construction is complete.

Additional progress has also been made on the installation of overhead electrification masts, the excavation of seven mountain tunnels in Palghar, the superstructure work on all stations in Gujarat, and the elevated stations in Mumbai.

Where does the Japanese side stand?

The project was discussed during Prime Minister Narendra Modi’s two-day visit to Japan last month. Japan has agreed to provide India with its latest E10 Shinkansen, which is its next-generation bullet train.

“The Indian side appreciates Japan’s offer to introduce, in the early 2030s, the E10 series of the Shinkansen that runs on the Japanese signalling system. To this end, it was concurred to immediately commence work necessary for early installation of the signalling, including the Japanese system, as well as for the introduction of the General Inspection Train (GIT) and one set of E5 series Shinkansen rolling stock,” reads the India-Japan joint statement from the visit.

The Indian Railways’ Integral Coach Factory in Chennai has also awarded the tender to the state-run BEML Ltd. to manufacture two high-speed trainsets with a test speed of 280 kmph, which will be somewhat similar to the Japanese bullet train.