How Sela Tunnel, at 13,000 ft, was built at -10 degree freezing temperature

The Tunnel in the upper reaches of Arunachal Pradesh bordering China was inaugurated by Prime Minister on March 9

Prime Minister Narendra Modi on Saturday dedicated the Sela Tunnel to the nation. He virtually inaugurated the Tunnel constructed at 13,000 feet from Itanagar.

The Sela Tunnel has been built at a cost of Rs 825 cr on the road connecting Tezpur in Assam to Tawang in Arunachal Pradesh.

The Tunnel will provide all weather connectivity to Tawang Region of Arunachal Pradesh. It will boost movement of Indian Armed Forces in the Tawang Sector.

Balipara-Charduar-Tawang Road on which this Tunnel has been constructed is an important axis connecting Tawang Region and provides connectivity to the hinterland upto Tezpur.

The road had various bottlenecks like Nichephu, Bomdila Town and Sela Pass, which have been addressed by BRO by construction of Sela and Nichephu Tunnels and Bomdila Bypass. 500 m long Nechiphu Tunnel was inaugurated and dedicated to the Nation on 12 Sep 2023 by Defence Minister Rajnath Singh. The foundation stone of Sela Tunnel was laid by PM Modi on 9 Feb 2019. The construction of tunnel commenced on 1 Apr 2019 and the first blast took place on 31 Oct 2019. The tunnel has been completed in just five years overcoming challenges of difficult terrain and adverse weather conditions. The Sela Tunnel System consists of two tunnels of lengths 1003 m and 1595 m respectively with 8.6 Km approach and link roads constructed at a cost of Rs 825 Cr. The second tunnel also has an escape tube adjacent to the main tunnel as per international norms. The escape tube constructed parallel to the main tube is connected with cross passages after every 500m. In case of emergency, this escape tube can be used for move of rescue vehicles and evacuation of stranded people. The tunnel has been designed for a traffic density of 3000 cars and 2000 trucks per day with a max speed of 80 km/hr.

Sela Tunnel will ensure All-weather connectivity to Tawang and forward areas bypassing the Sela top which will not only facilitate smoother movement of troops and supplies but also reinforces our defence capabilities in the region. Sela Tunnel will also herald a new era of economic prosperity for the Tawang region, fostering trade, tourism, employment and overall development. Earlier the route to Sela Pass had only single lane connectivity and treacherous bends due to which heavy vehicles, container trucks and vehicles with trailers could not get to Tawang. Moreover, due to adverse weather conditions, specifically in winters, evacuation of patients was adversely affected along the existing Sela Pass.

All this is now feasible with opening of tunnel. The completed Sela Tunnel System will reduce the travel distance by more than eight Km and travelling time by an hour. This Tunnel will improve the quality of life of the people living in the region, by providing easier access to healthcare, education and essential services in the region. Sela Tunnel has been constructed using New Austrian Tunneling Method (NATM) which is widely accepted and used in construction of tunnels worldwide especially for Himalayan Geology.

It is based on the Philosophy of “Build As You Go” and involves using the inherent strength of the surrounding rock mass to support the tunnel.

The execution of this mega project took over 90 lakh man-hours with an average of around 650 personnel and labours working every day for last five years. The enormity of the task could be judged by the quantity of 71,000 metric tons of cement, 5000 metric tons of steel and 800 metric tons of explosive that was used for construction.

A total of 162 plants and machinery were dedicated to the construction of this tunnel. Various challenges were faced by Project Vartak during the construction of Sela Tunnel. These included challenge of freezing temp up to -10° C and formation of Icicles inside tunnel which caused delay in concreting process thereby affecting the time plan.

Ingress of water during construction & cavity formation affected the progress of work. Restrictions due to COVID Protocol also affected the construction of the tunnel. Due to the cloud burst that happened in July last year, a lot of damages occurred and the resources had to be shifted for reconstruction of these damages. Out of five years it took to complete the project, approximately 762 days had high snowfall or rainfall and 832 days had temperatures below 0° C, creating immense challenges for the personnel executing the work. However, even with these challenges BRO was able to complete the tunnel in less than five years due to the efficient use technology, ground experience of executives and the hard work of civilian labour involved in the construction.

The Sela Tunnel Project has been constructed with the highest quality standards with a well prepared Quality Assurance Plan, prepared strictly as per IRC SP 91 and MoRTH Guidelines. The tunnel has state of the art safety features. The tunnel has ventilation system to maintain air quality and state of the art electro mechanical system including jet fan ventilation system, fire fighting devices, CIE norms based illumination system and SCADA controlled monitoring systems.

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