Overview

• The Devprayag-Janasu tunnel is India's longest rail tunnel and was completed using a Single Shield Hard Rock TBM, achieving a world-class excavation rate of 413 meters per month.
• Engineers faced significant challenges, including 1,500 liters per minute of water ingress and soft rock squeezing, which threatened the tunnel's stability and progress.
• A month-long effort involving chemical and cement grouting, as well as bentonite lubrication, successfully stabilized the tunnel, allowing work to continue safely.
• The tunnel is part of the 125-km Rishikesh-Karnaprayag Rail Link, 105 km of which runs through tunnels, designed to enhance connectivity in the geologically complex Himalayan region.
• This project marks the first use of a 9.11-meter diameter Single Shield TBM in the Himalayas, with advanced geological assessment techniques ensuring safe and efficient progress.