T49 is a 12.75 km-long tunnel and is going to be the longest tunnel of the Indian Railways. The south portal of Tunnel T49 is located in the Sumber Village at an altitude of 1,400 meters, while the north portal of the tunnel is located near Arpinchala Village at an altitude of 1,600 meters.
While executing the tunnel from the north portal, Afcons’ engineers excavated 4.07 km from a single adit. “This is the most critical and longest length executed by any agency from a single adit. No other agency in the entire USBRL project has excavated such a long distance from a single-phase,” Afcons’ Project Manager Chandra Shekhar Dixit said.
Amidst the challenge of working in extremely cold conditions, the team faced another major hurdle. There was water ingress of 40-50 liters per second which made tunneling extremely difficult. “Since we were working on a downward gradient, on average, we had to dewater almost 2 lakh KWH unit per month. The water ingress was due to numerous aquifers and nullahs crossing the tunnel alignment,” the Project Manager added.
Excavation began in 2015 under extremely poor geology. The original scope was later revised to accommodate an additional 3.6 km escape tunnel which brought about a change in alignment. The entire project was completed within the scheduled time.