Significance of Railways completing breakthrough for India’s ‘longest transport tunnel’ in Uttarakhand

At present, the longest rail tunnel in India is 12.75 km long, between Khari and Sumber Stations on the Katra-Banihal Section of the Kashmir line or the Udhampur-Srinagar-Baramulla Rail Link (USBRL). The longest road tunnel is the Atal tunnel on the Manali-Leh highway, which is 9.02 km long.

A major breakthrough achieved today.

The tunnel boring machine has made it through the longest transportation tunnel (T-8) in India which is 14.58 km long.

Rishikesh-Karnaprayag new line project.
📍Uttarakhand pic.twitter.com/4GA9Mw1D9G

— Ashwini Vaishnaw (@AshwiniVaishnaw) April 16, 2025

The significance

Beyond the larger project, the breakthrough matters because it signifies the first successful tunnel boring machine (TBM) use in the Himalayan terrain and the first by the Indian Railways. TBM is a special machine for excavating tunnels through hard rocks. Unlike the blasting method, it reduces the disturbance to the surroundings and the cost of lining the tunnel.

Along with TBM, the New Austrian Tunnelling Method (NATM) has also been used, involving controlled and small-scale excavation. NATM was earlier used for constructing tunnels on the Katra-Banihal section. The TBM has tunnelled 10.4 km in tunnel no. 8, with 4.11 km excavated through NATM.

A senior official of Rail Vikas Nigam Limited (RVNL), which is executing the project, said they faced several challenges. “The construction of a railway line in such a difficult terrain is always a challenge. First thing is the supply of all kind of material and machinery at a high altitude. The delivery of items must remain uninterrupted also so that that the critical works, such as this tunnel breakthrough, does not get affected. We have to ensure that Tunnel Boring Machine must navigate through difficult terrain and varying ground conditions without unscheduled stoppages, demanding high system reliability and responsive support. We faced major hurdle because on seasonal monsoon impacts such as landslide, road closures, etc. It is the 30 km long national highway through which the material was being supplied,” said the official.

Overall, the Indian Railways have increased their tunneling activity. A total of 468.08 km of tunneling has been done since 2014, which is 3.7 times of the total 125 km of tunneling done till 2014, officials said.

The rail link

The Rishikesh-Karnaprayag rail link project is 125.20 km long. Of this, 104 km or 83 per cent of it is in the form of tunnels. It is a single-line broad-gauge network. The alignment has 12 new stations, 16 main tunnels and 19 major bridges covering five districts – Dehradun, Tehri Garhwal, Pauri Garhwal, Rudraprayag and Chamoli – in Uttarakhand.

Rudraprayag line.

Apart from the 16 main tunnels, the project will have 12 escape tunnels of 97.72 km length and 7.05 km long cross passages. The escape tunnels are built alongside the main tunnel to provide a safe passage for people to evacuate in an emergency, like a fire or accident.

The project includes five important bridges, one each on the Ganga and the Chandrabhaga, and three bridges over the Alaknanda. The longest bridge in the project is Srinagar Bridge no. 9, which will be half a kilometre long. The highest bridge is the Gauchar Bridge, at 46.9 meters.

One section of the project has been operational since 2020. A total of 5.7 km between the existing Virbhadra station and Yog Nagri Rishikesh station was commissioned in March 2020.

A senior official of the Ministry of Railways said that out of the total target of constructing 213 km of tunnels, the work for 195 km is complete. Geologically, the tunnel predominantly traverses the Chandpur Formation of the Jaunsar Group. “The principal rock unit is Chandpur Phyllite, which includes Quarzitic and Schistose Phyllite with Intercalations of Quartzite Rocks and presence of quartz veins. Another thing is the presence of heterogeneous rock conditions — ranging from poor to medium and hard rock — poses significant challenges for excavation and support,” said the official.

Asked about when the project will become operational, the official said, “The tunneling works in the project are targeted to be completed by December 2025. Track works, electrical, OHE (Overhead equipment) and S&T (Signal & Telecommunication) works have been planned and will commence soon.”

Expected outcome

While several environmental experts have raised concerns over tunnelling in the Himalayas, the railways said its objective is to provide connectivity to hilly areas to reduce travel time and cost.

“The objective of providing a Rail link between Rishikesh and Karnaprayag is to facilitate easy access to pilgrimage centres of Uttarakhand. It will connect new trade centres of Uttarakhand and develop the backward areas. The rail lines will reduce travel time and cost, and open up opportunities for industrial development, cottage industry in the area, boost the economy and tourism prospects in the state. It will connect important sites such as Devprayag, Srinagar, Rudraprayag, Gauchar and Karnaprayag,” said a senior official of the Ministry of Railways.