Indian Railways' longest tunnel achieves breakthrough on Katra-Banihal section in J&K: Northern Railway officials

Northern Railway officials announced on Wednesday that the longest 12.758 km tunnel between Sumber and Arpinchala station on the Katra-Banihal portion of the Udhampur-Srinagar-Baramulla Rail Link (USBRL) project had achieved a line and level breakthrough, as per reported by IANS.

According to the news agency, the breakthrough was made on the T-49 tunnel, which would be the Indian Railways' longest tunnel, surpassing the 11.2 km-long Pir Panjal tunnel on the Banihal-Qazigund route, which was built by USBRL, officials said.

At a height of 1,200 meters, the south entrance of tunnel T-49 is located in the picturesque Sumber village, 45 kilometers from district headquarters Ramban. While North Portal is located at a height of 1,600 meters near Arpinchala village in Khari Tehsil.

The T-49 tunnel is divided into two sections: the main tunnel and the escape tunnel. It was built utilising the New Austrian Tunnelling Method, which is a contemporary drill and blast technology.

The tunnel's cross-section profile is changed to create a horseshoe form, IANS said.

Three adits — Urnihal Adit, Hingni Adit, and Kundan Adit — have been built to aid in the building of the longest tunnel. The tunnel has a 1 in 80 ruling gradient and a designed speed of 100 kilometers per hour.

An adit is a horizontal or almost horizontal passageway that leads to a wider subterranean excavation for ventilation, water disposal, or supplementary access.

According to international standards, the escape tunnel is connected parallelly to the main tunnel by cross passageways every 375 meters to assist rescue and repair operations, IANS reported.

"The work of construction was entrusted by Northern Railways to M/s IRCON International limited which has assigned works in two packages to Messrs HCC and M/s AFCONS," the official said.

The HCC is working on the 5.1-kilometer section from the south portal, while AFCONS is working on the 7.658-kilometer stretch from the north portal.

According to IANS, several issues were faced during construction, including a shear zone, perched aquifer, heavily jointed rock mass, rock squeezing problems, and considerable water ingress.