Atal Tunnel: Longest Highway Tunnel in the World

01 Dec 2021

Atal Tunnel is also known as Rohtang Tunnel, connects Manali to Leh and is the longest highway tunnel in the world. The long tube tunnel is spread across a stretch of 9.02km, at a height of 10,000 feet. It will reduce the travel time between Manali and Leh by 4 to 5 hours by shrinking the distance up to 46km.

The tunnel is named after former prime minister Atal Bihari Vajpayee and was being built as an ambitious project of the nation. One prime motive for its construction is the Manali-Sarchu-Leh streets remain closed from November to April due to snow accumulation in Rohtang Pass. The underpass aims to alleviate this issue by providing all seasons connectivity. It will not only furnish a tranquil traveling experience but also enhance tourism by attracting more tourists throughout the year. Hence, it will contribute to the economic growth and development of the frosty part of the country.
As mentioned earlier, the Atal Tunnel is one of the ambitious projects dwelling within the country which was proposed in the year 1983. Since 1983, it has passed various parameters and scrutiny when finally the commencement of the construction took place in 2010. The first shoot for the tunnel happened on August 29, 2010, at South Portal, close to Dhundi, and on October 4, 2010, at North Portal in Sissu. The South Portal of Rohtang Tunnel is situated at a distance of 25 km from Manali at an elevation of 3060m, while the North Portal is proximal to town Teling, Sissu, in Lahaul valley at a height of 3071m. 
For designing the tunnel, an agreement was assigned to Strabag-Afcons Joint Venture (SAJV). The beautiful tunnel with an estimated cost of ₹3,200 crores is a horseshoe-shaped tunnel having a total length of 8.802km. With an overhead clearance of 5.525m, the tunnel permits a speed limit of 80kmph. The tunnel is 10m wide having 8m wide pavement and 1m wide footpath on both sides. Due to the opacity of the mountains, blasting and digging technique was administered instead of using tunnel boring machines. New Australian Tunneling Method (NATM), alias Sequential Excavation Method (SEM) was deployed for blast and drill technique. The fundamental support is layered with the amalgamation of fiber-reinforced concrete and rock bolt. It has incorporated a Semi-transverse system of ventilation. 
Rohtang Tunnel encompasses several features to provide a smooth and safe ride through it. It has placed a fire hydrant every 60m. Keeping in mind the value of communication in today’s world, the tunnel has a telephone booth every 150m. It has emergency exists every 500m of 2.25m high and 3.6m wide. At a distance of every 1km, there is an air monitor maintaining ventilation. Concerning safety and security, there is CCTV installed every 250m. 
Constructing the longest highway tunnel in the world was not an easy task. The team contributing to creating the marvel had to face numerous challenges. Erection through a crystalline thrust precipitates the geological extremity of the native Himalayas. Frequent geological fluctuations due to the young mountains made it difficult as well. The winter season became the most daunting period to carry out the excavation in presence of excessive snow. Since excavation was done from both sides, during the winter season Rohtang Pass would be shut down making North Portal unavailable. Hence the excavation was done only at South Portal during winters. After excavation, discarding the excavated rocks and soil was another grueling task. Heavy ingress of water required strenuous efforts like continuous dewatering. Despite all these challenges, the constant dedication and rigor to build this marvel, the team has completed the project magnificently presenting one more achievement to the nation!

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