Uttarakhand tunnel collapse: A look at 5 plans to evacuate trapped workers | Explained

In a major breakthrough late Monday, a six-inch pipe was pushed through the rubble of the collapsed portion in the Silkyara tunnel in Uttarakhand. Later on Tuesday, audio-visual communication was also restored with the trapped workers. As many as 41 workers remain trapped after portions of the tunnel collapsed following a landslide on November 12. Since then, rescue operations are being carried out on a war footing.

However, rescue efforts have been slow, complicated by falling debris as well as repeated breakdowns of crucial heavy drilling machines, with the air force having to twice airlift in new kit, news agency PTI reported.

The five options

According to reports, there are five ways authorities are planning to evacuate those trapped inside the collapsed tunnel. The Ministry of Road Transport and Highways said earlier various government agencies have been involved in the rescue operation and have been assigned specific tasks. Five different agencies were detailed to carry out five different options. The area in which the workers are trapped is 8.5 metres high and 2 km long.

“Five agencies namely Oil and Natural Gas Corporation (ONGC), Sutluj Jal Vidyut Nigam (SJVNL), Rail Vikas Nigam Limited(RVNL), National Highways and Infrastructure Development Corporation Limited (NHIDCL), and Tehri Hydro Development Corporation Limited (THDCL) have been assigned responsibilities,” Anurag Jain, Secretary, Ministry of Road Transport and Highways, said.

Jain also explained the rescue plans in the video below:



Here’s a a deep dive into the five plans that the govt has on its card:

1. 1.2 metre-wide hole after vertical drilling

Rescuers plan to dig a 1.2 metre-wide hole vertically from above the tunnel. This will be done for a distance of 90 metres to reach the workers, the Hindustan Times reported on Tuesday. Arnold Dix said, “Vertical drilling will start once the site is prepared because for vertical drilling it is very important that it is done very accurately.”

The first vertical drilling machine already reached the Silkyara tunnel early Tuesday. Two more machines are expected to reach from Gujarat and Odisha in next two-three days, the report sapid. “The Satluj Jal Vidyut Nigam Limited (SJVNL) has brought a heavy drilling machine and is now at the tunnel site to being the vertical drilling operation,” PTI reported.

International Tunnelling and Underground Space Association president Arnold Dix is currently overseeing the ongoing rescue efforts at the Uttarkashi tunnel collapse. While speaking to news agency ANI, he said, “…we have multiple approaches to the rescue.”

2. Horizontal boring by NHIDCL

Engineers had been trying to horizontally drive a steel pipe, just wide enough for the trapped workers, through at least 57 metres (187 feet) of earth and rock that block their escape. But the giant earth-boring machine they were using ran into boulders it could not get through. “Drilling on that route was paused on Friday after a cracking sound created a panic situation”, officials was quoted as saying.

Now, the National Highway Infrastructure Development Corporation Limited (NHIDCL) team will recommence drilling from the mouth of tunnel from the Silkyara side. The horizontal boring will be done using the Augur boring machine.

3. Another vertical tunnel from the top

The Oil and Natural Gas Corporation (ONGC), having expertise in deep drilling, has been tasked to create another verticle tunnel at the 2.3-km mark. This tunnel will be nearly 325 metre deep and the machines for this operation was brought from the US, Mumbai and Ghaziabad.

4. Rescue from Barkot end

A 483-metre-long yet narrower tunnel will be made through the Barkot end of the tunnel by the Tehri Hydro Development Corporation using the conventional drill and blast method.

5. Another horizontal drilling by RVNL

The Ministry of Road Transport and Highways said in a press release Rail Vikas Nigam Limited (RVNL) is working on another vertical pipeline for the supply of essential items. The release said it was decided to lay a 900 mm pipe through the muck as it was the best and fastest possible solution as per the experts’ advice.

According to the Hindustan Times, the RVNL is doing micro-drilling from the left of the tunnel. This horizontal tunnel will be 1.2 metre-wide ad 168 metre long. It will meet the existing tunnel at round 300-metre mark from Silkyara side, the Indian Express reported.

The breakthrough

The tube used to deliver supplies to the men was successfully widened on Monday with the installation of a 15-centimetre (six-inch) pipe, through which the camera was sent down. It is hoped that a drone can also be sent down to assess the stability of the area where the men are trapped. Hot meals were also delivered through the new pipe for the first time.

Over a week into the incident, Uttarakhand Chief Minister Pushkar Singh Dhami said on Tuesday, “With the efforts of all agencies, experts, engineers, officials and people working there, we saw a big success last night (Monday, November 21). A six-inch pipe was inserted there. Through that, food is being sent to them (trapped workers). We pray to God for any of our options to succeed at the earliest and for our workers to be brought out.”

Rescuing workers top priority

The Chief Minister said Prime Minister Narendra Modi “is taking information from us every day…Everyone is giving their best”. In a post on X, Dhami said he told PM Modi that the workers are safe, while the prime minister underlined that the rescue mission is the topmost priority.

The collapse occurred on November 12 during the construction of a tunnel from Silkyara to Barkot, trapping 41 labourers due to a muck fall in a 60-metre stretch on the Silkyara side of the tunnel. The workers are believed to be trapped in a 2 km-built tunnel portion, which is complete with concrete work that provides safety to the workers. This portion of the tunnel has access to electricity and water.

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Updated: 21 Nov 2023, 04:19 PM IST

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