India's longest rail tunnel: Tunnel boring machine operators cut through treacherous Himalayas

New Delhi: India's longest rail tunnel, stretching 14.57 km between Devprayag and Janasu in Uttarakhand, has seen the light of the day due to the perseverance of two tunnel boring machine operators who worked day and night to cut through treacherous mountain terrains and completed the project ahead of schedule.

The tunnel is part of the ambitious 125-km Rishikesh-Karnaprayag Rail Link Project, which the Railway Ministry has entrusted to Rail Vikas Nigam Limited to operationalise by December 2026

"It was a roller coaster ride in the real sense," recalls Baljinder Singh, 44, a TBM operator employed with construction firm Larsen & Toubro (L&T).

One of the most challenging times, he said, came when a massive landslide blocked the tunnel path, forcing them to operate the tunnel boring machine at full power deep inside the mountain.

"We normally operate the TBM at 50,000 to 60,000 kilo Newtons of force, but during that time, when it got stuck around 3.5 km inside due to a sudden landslide, I had to apply the machine's full power -- 1.3 lakh kilo Newtons -- to clear the debris," he said.

"The situation was so critical that it looked like the project might be shelved. It was our experience and patience, along with the technical and moral support of the whole team of over 200 experienced staff, that pulled us through," Singh added.

His colleague Ram Avtar Singh Rana, 52, another veteran TBM operator, worked shoulder-to-shoulder with him to save the project.

"It took nearly 10 days of non-stop struggle, working round-the-clock in 12-hour shifts to push the TBM through the muck. It was a huge relief and a joyous moment for the entire team when we finally cleared the blockage," Rana said.

"We operated a German-made TBM named Shakti, running it non-stop in rotation, as stopping it for even a moment could have spelt disaster during that time," he added.

According to him, even during normal operations, they rested the TBM only for a brief while and worked almost 24x7 to complete the 14.57 km rail tunnel on April 16, 2025, 12 days ahead of schedule. .

L&T officials said that was the first time a TBM was used for a railway project in the Himalayan region. Such machines were previously used in the mountains for hydroelectric tunnels.

"The terrain and geology made the task uniquely demanding," Rana said.

While Singh brought to the project 22 years of TBM operating experience, mostly in mountainous areas like Jammu and Kashmir, Rana too had worked extensively on metro tunnelling projects in Mumbai and other challenging environments.

Singh said operating a TBM in a tunnel is not easy as the operator leads the way into uncharted territory while the entire engineering team follows his path.

Asked whether the job was life-threatening in the event of a tunnel collapse, Singh said that proper grouting and stabilisation of the excavated section significantly reduced the risk.

"The TBM we used is about 140 metres long, including all its components. It has a 13.75 metre cutter head with 55 cutting discs. As we progress, the civil team stabilizes the newly excavated area, reducing the chance of collapse," Rana said.

While Singh and Rana completed the upline tunnel, another team -- Chandrbhan Bhagat and Sandeep Mishra -- worked simultaneously on a 13.09 km downline tunnel, running parallel at a 25-metre distance. This second tunnel achieved a major breakthrough on June 29, 2025.

"After finishing the upline tunnel, all four of us focused on the downline, using the second German TBM named Shiv. Together, we set a new world record by advancing 790 metres in a single month (31 days)," Rana said.

According to L&T officials, the total tunnelling work spans 30 km, including main tunnels, escape tunnels, cross-passages, and niches, making it one of India's most complex and significant infrastructure undertakings in recent years.

While 70 percent work (21 km) was done through TBMs, the remaining 30 percent (9 km) was completed using drill and blast (also known as New Australian Tunnelling Method)

"There are many more tunnels in the 125-km long project, however, these two are the biggest ones," officials said.