Nov 12 is when India celebrated Diwali, its new year and festival of lights, but it proved to be a dark day for 41 construction workers trapped due to falling debris inside the 4.5-km Silkyara Bend-Barkot tunnel in the mountainous northern state of Uttarakhand
The tunnel, part of a $1.7 billion, 900-km highway project to connect four major Hindu pilgrimage routes, is in a region with a geology of fractured rocks prone to landslides and seismic activity. .
Despite assurances the trapped workers would be rescued by Nov 22, Lt. Gen Syed Ata Hasnain, a member of the National Disaster Management Authority, said at a hurried Nov. 23 press conference in Delhi that auger machines drilling horizontally toward them now face “more obstacles encountering girders or concrete blocks that could take more time” for the remaining 17 meters. Some lattice structures had fallen from above, “increasing the length,” he said.
“Be prepared for more time for the operation to be completed,” Hasnain added, suggesting a long-haul delay could be likely. “Geology is the enemy.” He refused to give a timeline.
Multiple obstacles have developed for rescuers, including encountering an iron girder in the last stage of digging. News agency PTI reported that the platform, on which the 25-ton auger with a drilling speed of around 4 m per hour was mounted, had developed cracks and was being stabilized.
Arnold Dix, president of the Switzerland-based International Tunneling and Underground Space Association and one of several international consultants working with the rescue effort, said “the auger machine has broken down" but was under repair and set to be back in service by Nov. 24.
Based in Australia, Dix is an attorney with technical background and special expertise in underground work. Claiming 30 years experience in engineering, geology, law and risk management, he said he was confident the rescue would succeed. In a separate interview with the BBC, Dix described some scenes in the tunnel "a bit like a war zone with just equipment and everything everywhere." He said there were 50 or 60 engineers, technicians and surveyors at the scene with "everyone ... busy preparing the equipment that failed yesterday."
To reach the workers, the rescuers deployed a pipejacking rig with a central auger to dig through the rubble to create a safe escape tube. But faced with crushed machinery and steelwork, the auger had "extreme difficulties getting through the avalanche," said Dix. "It ripped itself, literally, out of the mountain. It couldn't do the job."
The consultant added that "If it fails, and it’s already failed three time, we've got other ways to get inside ... that [are] going to take even longer. All the people [here] including myself ... are in extreme danger because the avalanche that has already occurred has crushed part of this tunnel."
A Historic Effort Continues
The rescue now is recognized as the largest in India’s history in terms of the number of trapped workers and rescue timeline and complexity. The effort now involves input from major government agencies associated with disaster management and construction, as well as Indian Army and international tunneling experts, including some who were involved in the cave rescue of 12 young boys from a soccer team and their coach in Thailand in 2018. Norwegian Geotechnical Institute experts are also involved in the tunnel rescue.
Initial efforts to drill to the workers failed as a locally sourced machine was not powerful enough to drill through the rock. Work was also stopped for two days following a cracking sound possibly caused by falling rock due to an earthquake and the unstable nature of the collapsed tunnel environment.
Two U.S.-made auger machines were flown in by the Indian Air Force and reassembled on site. They drilled around 46 m as 6-m sections of 800-mm-dia. pipes were welded to provide an escape passage. But recent setbacks with this approach have the rescuers considering other options as well.
ENR has confirmed that officials are nervous about the horizontal drilling approach despite calling it the best bet earlier. An option of vertical drilling down to 300 m is ready to start using an approach road for heavy machines that was constructed by India's Border Road Organization within 48 hours Drilling could take ten days. A plan to blast the other end of the 480-m long tunnel could take up to 45 days. according to Hasnain.
He said survival rations were being sent through compression via a 4-in. pipeline, with a new 6-in. pipeline also installed to transport hot-cooked food.
The tunnel crisis occurred just three months after 20 workers and engineers died on the 700-km Nagpur-Mumbai Samruddhi Expressway when a gantry crane launching box girders collapsed. Charges have been filed against subcontractors Navayuga Engineering and VSL Pvt Ltd. The former, which is building the tunnel for the National Highways and Infrastructure Development Corp Ltd., did not respond to requests for comment.
For some in India's construction sector, the latest incident has again highlighted a lack of focus on following strict safety guidelines rather than concentrating on cost-cutting. “India’s construction industry lacks skills, has high work hours for engineers, and salaries are much lower than their Western counterparts,” Chandra Shekhar Pant, MEP head at a Larsen & Toubro project near Delhi, told ENR.
The drill blast method of tunnel construction is challenging, particularly in the Himalayan region, as rock is soft and landslides are common, he explains. “A rescue pipe of at least 16-mm thick with 1,000 mm dia. and 30 m in length should be placed in a conventional tunnel such as this before further drilling, which in a crisis, can create a conduit for evacuation," Pant said.
An environment impact assessment—required for every highway over 100 km—had been avoided on this particular project by dividing it into 53 packages, Himanshu Khattar, an environmental advocate familiar with Himalayan geology told ENR. “Full diligence studies are a must if disasters are to be avoided,” he said.
Despite setbacks, Dix is optimistic about the outcome, telling the BBC he anticipates the trapped workers will "be home singing Christmas carols."