Rishikesh-Karnaprayag Tunnel T-8

Rishikesh-Karnaprayag Tunnel T-8 Latest News

Tunnel No. 8 (T-8) is set to become India’s longest rail transportation tunnel at 14.57 km, surpassing the current longest T-50 (12.77 km) on the Udhampur-Srinagar-Baramulla Railway Link.

About Rishikesh-Karnaprayag Tunnel T-8

• T-8 is a twin tunnel situated on the Devprayag–Janasu stretch of the 125-km Rishikesh–Karnaprayag Broad Gauge Rail Link Project, in the state of Uttarakhand.
• The project is being implemented by Rail Vikas Nigam Limited (RVNL), a Navratna PSU under the Ministry of Railways, and executed by Larsen & Toubro (L&T).
• Over 83% of the 125-km alignment—about 104 km—comprises tunnels, making it one of the most underground-intensive rail projects in India.
• The rail line will connect Rishikesh to Karnaprayag, cutting travel time from 7 hours to just 2 hours, enhancing connectivity across five districts: Dehradun, Tehri Garhwal, Pauri Garhwal, Rudraprayag, and Chamoli.

Engineering and Technological Highlights

• Tunnel Boring Machines (TBMs) were used for the first time in Himalayan rail projects to excavate 10.4 km of T-8. These 2200-tonne machines were imported from Germany, transported via 17 shipments and assembled on site.
• The diameter of the TBM used for T-8 was 9.1 metres, larger than the 6-metre TBMs used in the Delhi Metro.
• The New Austrian Tunnelling Method (NATM) was used to excavate the remaining 4.11 km of the tunnel, especially in non-uniform geological zones.
• Three advanced technologies were deployed for safety and precision:
  • Tunnel Seismic Prediction (TSP) to detect geological faults.
  • Torque Box for multidirectional boring capability.
  • Void Measurement to detect and fill gaps behind tunnel linings.

Source: IE

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