A major milestone was achieved on the Udhampur Srinagar Baramulla Rail Link project (USBRL) on Feb 15, 2022, with the breakthrough of Tunnel T49 between Sumber and Arpinchala Stations on the ongoing Katra-Banihal Section. T49 is a 12.75 km-long tunnel and is going to be the longest tunnel of the Indian Railways surpassing the Peer Panjal Tunnel of 11.2 km on the Banihal-Qazigund section. The south portal of Tunnel T49 is located in the picturesque 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 metres.
Breakthrough of India’s Longest Railway Tunnel
Afcons, a key player in the strategic project, made it to the breakthrough point from the north portal despite numerous geological challenges. Describing the momentous occasion, Afcons’ Project Manager Chandra Shekhar Dixit said, ”This is an incredible achievement for the Indian Railways, for the nation, and for Afcons. The project team has worked extremely hard for this day. Afcons has constructed 7.32 km of the 12.75 km-long tunnel amidst various geological and weather-related challenges.”
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 entire USBRL project has excavated such a long distance from a single phase,” Dixit said.
Amidst the challenge of working in extreme cold conditions (as low as -10 degree centigrade) during the winter months, the team faced another major hurdle. There was water ingress of 40-50 litres per second which made tunnelling 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 said.
More than 60 per cent of the tunnel length was executed in very poor rock class. But extremely high deformation was observed in a 1.5 km stretch of the tunnel. To overcome this, the team adapted various construction techniques like enlargement of tunnel profile and introduced steel fibre reinforced concrete to speed up the progress. “We began excavation in 2015 and throughout excavated 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. But we were able to complete the entire project within schedule,” Dixit said.
“This tunnel is a major achievement for Indian Railways and for Afcons. From heavy snowfall and heavy rains which impeded vehicle movement every year to local issues and extremely poor geology, we are happy to have passed them all and complete a major assignment for the nation,” he added.
Afcons Infrastructure Limited is a construction and engineering company headquartered in Mumbai and part of Shapoorji Pallonji (SP) Group which has a legacy of over 150 years. Afcons has projects in over 22 countries and is one of India’s fastest growing infrastructure company.