MUMBAI: Afcons Infrastructure Limited (Afcons) was recently conferred with the prestigious CII Industrial Innovation Award for its pioneering engineering solution at the world’s longest highway tunnel, in Manali, Himachal Pradesh. The iconic Atal Tunnel, which is constructed at an altitude of 3,000m (10,000 ft) above sea level, is an engineering marvel in the Himalayas. The 9.02km tunnel is a game-changer for Lahaul & Spiti as it provides safe, all-weather connectivity to the remote region with Manali, and eventually with the rest of India.
Constructing this tunnel was nothing short of a roller-coaster ride. The excavation was extremely challenging due to extreme weather and poor geological conditions. At the South Portal, near Dhundi, extremely fractured and pulverized rock led to the complete collapse of the tunnel face at the Seri Nala Fault Zone. Almost 8,000 liters of water per minute gushed into the tunnel along with muck flooding the excavated area. This slowed down tunneling progress from 120m per month to almost 20m per month.
The problem was finally solved by Afcons with a unique innovation in the form of a pipe roofing system. The heavily damaged roof was strengthened using a seamless array of long pipes (12-15m) to build an umbrella-like structure in the crown. While most of the area was covered by a single row of pipe roofing, in extremely weak zones, double rows were created. Slow, yet steady, progress was made, and 40,000m of single and double pipe roofing was installed.
“The Atal Tunnel is an engineering marvel in its true sense. Never in India before a tunnel of this scale and complexity have been constructed. Although the Seri Nala Fault Zone was 526m, the excavation took four years to complete. Due to heavy water ingress, the face of the tunnel literally used to flow like a river of mud and boulders. Securing the tunnel face under these circumstances and excavating further was a huge task,” said Satish Paretkar, Director and BU Head, Hydro & Underground Works, Afcons.
“While overcoming the Seri Nala Fault Zone was daunting, this is one of the few tunnels in the world, and the first in India, that has been built with an emergency escape tunnel below the main tunnel. Passages have been provided at every 500m where a stairway leads to the escape route. In times of adversity, the escape tunnel can be used to evacuate people,” Paretkar added.
The Atal Tunnel was inaugurated by Prime Minister Narendra Modi in October 2020. The tunnel bypasses the treacherous Rohtang Pass, reduces travel time, and ensures uninterrupted movement of people and supplies. It also opens a new chapter in the lives of locals at Lahaul & Spiti by ending their six-month isolation during the winter months.
Afcons Infrastructure Limited is a construction and engineering company headquartered in Mumbai and part of Shapoorji Pallonji (SP) Group which has a legacy of over 150 years. Afcons has projects in over 22 countries and is one of India’s fastest-growing infrastructure companies. The company has launched a massive vaccination drive to safeguard its employees, their families, workers, and locals in their respective regions both in India and overseas.