Northern Railway achieves a milestone of breaking through of India’s longest Escape Tunnel T-49 (12.895 km) in J&K

Umesh Tiwari
New Delhi: Ashutosh Gangal, General Manager Northern Railway, on Thursday said that Northern Railway has achieved a major milestone in the USBRL project on 15.12.2022 by executing break-through of India’s longest Escape Tunnel T-49 between Sumber and Khari Station on the ongoing Katra-Banihal Section of the USBRL project in J&K after successfully negotiating major cavity formation.
In a statement issued on Thursday here Ashutosh Gangal said that the length of the escape tunnel T-49 is 12.895km, adding that this is the longest escape tunnel of India and the line and level of the tunnel are precisely achieved during the breakthrough of the Escape Tunnel the presence of S.P. Mahi Chief Administrative Officer/USBRL, with his team of officials and staff.
“Escape Tunnel T-49 is a modified horseshoe-shaped tunnel connecting the Sumber Station yard on the Southside &Tunnel T-50 after crossing Bridge no.04 over KhodaNallah on the North side, at Khoda village”, the above referred Statement reads, adding that “the elevation of the South end at Sumberis is approx 1400.5 m and of the North end is 1558.84 m”, stating therein further that “the ruling gradient inside the tunnel is 1 in 80”, adding further therein that “the boring was done from various faces from South portal, north portal and through three Aditsi.e.Urnihal (323 m), HingniAdit (280m) &Kundan Adit (739m)”.
Disclosing that the Tunnel T-49 is a twin tube tunnel comprising the Main tunnel (12.75 Kms.) & Escape Tunnel (12.895 Kms.) connected with 33 Nos. cross-passages at every cross passage, the Northern Railways in it’s statement further said “ the main tunnel mining was already completed and final lining works are progressing at rapid pace”, adding that “ the Tunnel is constructed as per International standards, in which provision of an Escape Tunnel has been made to facilitate rescue and restoration works in emergency cases”.
Northern Statement in it’s above quoted statement also said that the Escape Tunnel passes through the Ramban formation of the Young Himalayas and besides this various distributaries/Nallahs of Chenab River like Khoda, Hingni, Kundannallah etc. Cross all along the alignment, making mining more of a highly challenging task, adding that “Several Challenges were encountered in the course of construction such as shearzone, perched aquifer, and highly jointed rock mass, rock problems of excessive squeezing and heavy ingress of water”.
Stating that on the north end, the tunnel alignment passes through a very weak shear zone of carbonaceous phillite, Northern Railways in it’s statement further said “the tunnel mining was very challenging and several surprises were met during tunneling, adding that “Excessive deformations were recorded during tunneling at several locations between Kundan and Seeran, but these challenges were successfully tackled professionally”, stating therein further that “Also a major cavity was encountered in escape tunnel on 21.03.2021 at Ch. 12/538 near the north portal due to extremely poor rock mass, the strength of Rock mass was not more than 5 MPA and RQD (Rock quality designation) 10, with damp to wet Ground Water Conditions”.
Northern Railway in it’s statement further more said that the calculated RMR (rock mass rating) is 18, GSI (geological strength index) is 26 and Basic RMR (Rock Mass Rating) is16, adding that the vertical overburden near the cavity location was 150 m and the size of the cavity was about 3 m long and 15 m high from the crown, continuous flow of mass was also witnessed and tunnelling in ET (Escape Tunnel) was subsequently suspended”.
The tunnel face was immediately stabilised and face was sealed detailed insvestigation was carried out and detailed methodology was finalised to attend to the cavity and the work was successfully carried out by negotiating the cavity.
Stating that the tunnel has been constructed by the New Austrian Tunnelling Method (NATM), which is a modern technique of drill and blast processes. Although the boring work of the tunnel, started from both directions upto the hand-shaking point, the precision of both ends meeting at one point flawless, Northern Railways in it’s statement said that this is the result of meticulous planning and precise execution of tunnelling work, the line and level of the tunnel perfectly matched in both portions after the break-through.
“The team of experienced engineers of Northern Railway successfully negotiated all challenges and achieved the major milestone of the breakthrough of the Escape tunnel”, reads the Northern Railways Statement, adding that “during the construction activities of the tunnel, more than 75% of workers from nearby villages were engaged in various construction activities, thereby ushering a positive change in the overall socio-economic landscape of the region”.
Stating that out of the total 272 Km length of the Udhampur-Srinagar-Baramulla Rail Link Project (USBRL Project), 161 Km has already been commissioned and operationalized. The work of balance 111 Kms, the Norther Railway in it’s statement said that the intervening stretch between Katra- Banihal is under progress at a rapid pace. Katra –Banihal Section is traversing through the hilly terrain of the lower Himalayas in which weak Geology, remoteness & inaccessibility of the area, weather conditions, landslides, and shooting stones on access roads are major challenges, Stating therein further that it has several major bridges and very long tunnels which are under construction at different stages.
It is worthwhile to mention that T-49 tunnel (12.75 km) from Sumber to Seeran village in Khari Tehsil area of Ramban district of Jammu and Kashmir UT is the longest transportation tunnel in the country. It is noteworthy to mention that there are three other tunnels on this project, the length for which are close to that of tunnel T-49 and details for these are as follows:
● Tunnel T48 = 10.20km (Breakthrough already achieved) between village Dharam- Sumber station
● Tunnel T15= 11.25 km between Sangaldhan – Basindhadar stations
● Pirpanjal Tunnel= 11.2km between Banihal – Qazigund station