India’s Longest Rail Tunnel Between Devprayag and Janasu Completed Amid Major Challenges:

Suspense Crime, Digital Desk : Also, during the weekend, Larsen & Toubro (L&T) reported that the longest rail tunnel in India from Devprayag to Janasu in Uttarakhand faced severe near collapse risks during its construction.

In an interview with PTI Rakesh Arora, Project Director shared, “Shakti”, the tunnel boring machine TBM encountered a catastrophic water ingress incident five kilometers into the mountain.

Water bursting at a dangerous 1,500 liters per minute flooded the tunnel housing approximately 200 personnel.

Arora described it as one of the toughest phases of the project with possible risks ranging from flooding to the entire structure collapsing.

Unfortunately, water relief tunnel construction took approximately a month post start to reach operational parameters.

Immediate measures such as chemical grouting and cement grouting alongside rock stabilization and suppression of water due to severe chemical relief had to be employed even though the rock grout condition needed to be drastically improved.

He explained the high surrounding soft rock posed immense pressure risk which was only solved by increase advance excavation and bentonite slurry lubrication on the TBM shield interface.

Cement grouting dramatically improved rock grout conditions allowing water pressure relief to be instantaneously stablizing the entire structure.

Bentonite enabled soft rock sealing storm enabling water pressure to be alleviated while sustaining pouring cement.

Soft rock failure prevention enhancer enabled super hexodyne fuel enable cement pressure straining accumulation prompt stability of the entire structure to hugely reduce.

The Devprayag-Janasu Tunnel was inaugurated on the 16th of April 2025 by Minister of railways Ashwini Vaishnaw, Chief minister of Uttarakhand proudly Dhami, and other famous personalities marking monumental achievement for them and the countr.

Key highlights:

Along with the rest of the Rishikesh-Karnaprayag Rail link project of 125 km the tunnel forms the core of the project.

This tunnel of rail is deemed the longest in India, at the same time being one of the fastest to be constructed on a global scale.

As a Single Sheath Hard Rock Tunnel Boring Machine, it's the first to be introduced in the Himalayas with a 9.11m diameter.

As fully outlined by Rail Vikas Nigam Limited (RVNL), TBM technology was employed for 10.49 km of the tunneling with a traditional drill and blast approach for the rest of the construction.

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As stated by Mr. Pradeep Gaur, commander of RVNL, the Devprayag Janasu tunnel was completed in record time of 413 meters per month, earning it the title of second in the world.

Spain currently holds that record as the Cabrera tunnel with a double shield TBM stands at 423 meters a month.

Like most of the tunneling feats of India, this comes with severely difficult geological features of the region which in regard to the these heights makes it a feat of engineering.

Transportation and reconstructions of the Himalayan range are a challenge of distinctive magnitude

The Integrated Transport Project Karnaprayag-Rishikesh has 13km of shaft yards, 105km of tunnel, 3km of bridges, and 4km of cross passages.

Mr. Arora pointed out that the two prime TBM problems in these tunnels are dewatering and positing of soft squeezing rock formations.

Essentially, a stuck TBM results in abandoning the project.

Safely Excavating Tunnels Using Modern Techniques

In order to confront unknown geology, manual probing and tunneling seismic prediction were used:

- Manual Probing: Includes drilling with a range of 60 meters ahead of a tunnel and evaluating the various penetration rates to determine the type of rock.

- Tunnel Seismic Prediction (TSP): Accomplished using seismic waves to establish the conditions of the rock 100 meters to the front and 15 meters on either side.

- Muck Analysis: Accomplished while studying the sample rock materials that were excavated to determine the underground rock’s behavior.

Through these scientific processes, excavation became easier and faster through one of the world’s most complex terrains.