Challenges faced during construction of the Sela Tunnel in Arunachal

Guwahati: Prime Minister Narendra Modi on Saturday virtually inaugurated Arunachal Pradesh’s Sela Tunnel project from the state’s capital Itanagar. The Sela Tunnel lies on the road that connects Tezpur in Assam with Tawang in Arunachal Pradesh.

The tunnel has been constructed for Rs 825 crore and lies at an altitude of 13,000 feet above sea level. The tunnel will bypass the treacherous Sela Pass which is located at an altitude of 13,700 feet above sea level. The tunnel is an important axis connecting Tawang with the rest of India.

The foundation stone of Sela Tunnel was laid by Prime Minister Narendra Modi on 9 February 2019. Its construction works commenced on 1 April 2019 and the first blast took place on October 31 of the same year. The tunnel has been completed in just five years overcoming all the challenges including difficult terrain and adverse weather conditions.

Various challenges were faced by Project Vartak during the construction of the Sela Tunnel. These included the challenge of freezing temperatures up to -10° Celsius and the formation of Icicles inside the tunnel which caused the delay in the concreting process thereby affecting the time plan.

Ingress of water during construction and cavity formation affected the progress of work. Restrictions due to COVID-19 protocol also affected the construction of the tunnel. Due to the cloud burst that happened in July last year, a lot of damage occurred and the resources had to be shifted for reconstruction of these damages.

Out of the five years it took to complete the project, approximately 762 days had high snowfall or rainfall and 832 days had temperatures below 0° Celsius, creating immense challenges for the personnel executing the work.

However, even with these challenges, the BRO was able to complete the tunnel in less than five years due to the efficient use of technology, the ground experience of executives, and the hard work of civilian labour involved in the construction.

The Sela Tunnel system consists of two tunnels with lengths of 1,003 metres and 1,595 metres. 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 500 metres.

In case of emergency, this escape tube can be used for the movement of rescue vehicles and evacuation of stranded people. The tunnel has been designed for a traffic density of 3,000 cars and 2,000 trucks per day with a maximum speed of 80 kilometre per hour.

The Sela Tunnel will ensure all-weather connectivity to Tawang and forward areas bypassing the Sela Pass which will not only facilitate smoother movement of troops of the Indian armed forces and supplies but also reinforce India’s defence capabilities in the region.

It 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, especially in winter, the evacuation of patients was adversely affected along the existing Sela Pass.

All this is now feasible with the opening of the tunnel. The completed Sela Tunnel system will reduce the travel distance by more than eight kilometres and travelling time by an hour. The Tunnel will also improve the quality of life of the people living in Tawang by providing easier access to healthcare, education and essential services in the region.

The Sela Tunnel has been constructed using the New Austrian Tunneling Method (NATM) which is widely accepted and used in the 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 labourers working every day for the last five years. The enormity of the task could be judged by the quantity of 71,000 metric tonnes of cement, 5,000 metric tonnes of steel, and 800 metric tonnes of explosives that were used for the construction of the tunnel. A total of 162 plants and machinery were dedicated to its 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 and a ventilation system to maintain air quality and a state-of-the-art electro-mechanical system including a jet fan ventilation system, fire fighting devices, CIE norms-based illumination system, and SCADA-controlled monitoring systems.

After dedicating the Sela Tunnel to the nation, Prime Minister Modi flagged off the first civilian convoy consisting of two buses from Tawang and felicitated the BRO personnel and casual paid labourers involved in the construction of the Sela Tunnel.

The Prime Minister also lauded the efforts of the BRO in providing last-mile connectivity to the border region. He praised the workers of BRO for constructing an engineering marvel in such difficult terrain under extremely trying conditions.