India rescue race goes on; further slides feared16 November 2023
Tunnelling efforts to rescue trapped workers continue to test how to delicately excavate through collapse debris in northern India amidst fears there could be more ground movement in the road tunnel and around the portal.
Successful jacking of a 200mm-diameter steel pipe helped rescuers move forward with fresh air and other support to 40 workers trapped since the weekend after an extensive collapse inside the tunnel works for the Silkyara Bend-Barkot road project.
However, efforts to jack a larger, 900mm-diameter pipe through the collapse debris – and also to excavate with a 800mm auger – in a bid to create an initial, temporary escape route have not made progress due to the collapse boulders. Tunnellers on the task are trying to develop alternative safe excavation options, ITA President Arnold Dix has posted on LinkedIn.
But amidst the works there are concerns of further geological instability in the immediate area.
Dix told T&T: “There is extreme concern about remobilising of the entire portal and first hundreds of metres of the tunnel.”
At the weekend, reprofiling works had been undertaken in part of the tunnel prior to the local collapse. The collapse occurred over a longer section of the tunnel than where the reprofiling works were undertaken. 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).
Silkyara Bend-Barkot Tunnel is located in the state of Uttarakhand, in the north of the country. Geology is complex in the region. The 4.5km-long tunnel project is being developed by NHIDCL to be an all-weather route and reduce travel distance by about 20km between Dharasu and Yamunotri.
NHIDCL is developing the two-lane, bi-directional road project for the Ministry of Road Transport & Highways. It awarded the contract in 2018 to Navayuga Engineering Co Ltd to build, operate and maintain the road link. The contract includes the tunnel plus a short approach road.
The Covid pandemic affected infrastructure development and construction schedules across the world. The original completion date for Silkyara Bend-Barkot Tunnel was mid-2022. 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 tonnes of debris, for the escape tunnel. But uncertainty over geology remains.
Dix added: “The co-operation between the world’s tunnelling 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.
“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.”