By Lynda Myer
While there is a significant fear of more ground movement in the road tunnel and around the portal, tunneling efforts to rescue trapped workers continue to test how to delicately excavate through collapse debris in northern India.
Through a successful jacking of a 200mm-diameter steel pipe, fresh air and other support were provided for 40 workers who have been trapped since the weekend after an extensive collapse inside the tunnel works for the Silkyara Bend-Barkot road project.
However, in order to create an initial, temporary escape route, attempts to jack a larger 900mm-diameter pipe through the collapse debris, digging with 800mm auger in a bid have not made advance due to the collapse boulders. As ITA President Arnold Dix has posted on LinkedIn, tunnellers on the task are trying to develop alternative safe excavation options.
But amidst the works there are concerns of further geological instability in the immediate area.
Dix told T&T: “There is extreme concern about remobilizing of the entire portal and first hundreds of meters of the tunnel.”
The location of this collapse was over a longer section of the tunnel than where the reprofiling works were undertaken, which was done in part of the tunnel prior to the local collapse at the weekend. The number of workers inside the tunnel at the time of the collapse was obtained from the entry register, said the National Highways and Infrastructure Development Corporation Ltd (NHIDCL).
Being placed in the state of Uttarakhand, in the north of the country, Silkyara Bend-Barkot Tunnel is located in complex geology in the region and with 4.5km length this project is being expanded by NHIDCL to be an all-weather route and reduce travel distance by about 20km between Dharasu and Yamunotri.
In 2018, the contract of building, operating and maintaining the road link was granted to Navayuga Engineering Co Ltd, whereas NHIDCL is developing the two-lane, bi-directional road project for the Ministry of Road Transport & Highways. The contract includes the tunnel plus a short approach road.
Considering that the infrastructure development and construction schedules across the world was affected by the Covid pandemic, original completion date for Silkyara Bend-Barkot Tunnel that was mid-2022 was delayed and the most recent published schedule gave an expected completion of mid-2024, but this was prior to the tunnel collapse at the weekend.
The tunnel is understood to be otherwise in good condition – leaving the challenge to be focusing on inserting the larger steel pipe through the thousands of tons of debris, for the escape tunnel. But uncertainty over geology remains.
According to Dix: “The co-operation between the world’s tunneling experts – in solidarity with the Indian experts managing this extremely demanding rescue emergency – is testament to our industry’s spirit of compassion and international co-operation. Our thoughts and prayers are extended for the well-being of those tunnellers trapped, their families, friends, colleagues, and communities, and the hard-working rescuers.”
He also added: “This area of the world is extremely geologically active – and the portals vulnerable to extreme landslide events. I endorse careful rescue operations in such extreme circumstances and personally have great confidence in the rescue co-ordinated efforts. God speed – and all kind thoughts, skill and prayers on this increasingly complex rescue mission through extreme avalanche materials.”
