Manual drilling and excavation horizontally using the rat-hole mining method started on Monday at the Silkyara tunnel in Uttarkashi to evacuate the 41 workers trapped inside for 16 days, people familiar with the matter said, adding that six rat-hole mining experts have been deployed for the rescue operation.

The development came after parts of a US-made auger machine, which drilled up to 46.8 metres through the debris, got stuck in the rubble on Friday, forcing officials to focus on an alternative option, such as vertical drilling and rat-hole mining technique.

Also read: Double push for tunnel rescue as wait continues

Officials involved in the rescue operation said that the horizontal drilling through the last 10-12 metres of debris of the collapsed portion of the tunnel will be done manually by a team of six rat-hole miners from Madhya Pradesh. They began the drilling from inside the pipes, 800- and 900-mm in diameter, pushed inside the tunnel to evacuate workers, on Monday.

“Three of us will go inside the tunnel, one will do the drilling the other will collect muck and the third one will push the muck through the trolley,” Rakesh Rajput, one of the rat-hole miners from Madhya Pradesh, said. “The 41 men are also labourers and we all want to bring them out.”

Rat-hole mining is a primitive method of extracting coal deposits through narrow, horizontal passages, prevalent in Meghalaya. The term “rat hole” refers to the narrow pits dug into the ground, typically just large enough for one person to descend and extract coal. The name comes from its resemblance to rats burrowing through narrow holes.

Parsadi Lodhi, another rat-hole miner and resident of Jhansi who has joined the rescue operation, said, “I have been doing this work for last 10-12 years in Delhi and Ahmedabad. But it will be first time when we will use our skills to rescue men trapped in a tunnel.”

Elaborating the rescue process using this technique, Lodhi said, “We would enter the rescue pipes and use the hand-held tools to remove debris… There is no reason for us to be scared to do this job. These are 800-mm pipes, we have entered in narrower 600-mm holes.”

Stating that there are about 10 to 12 metres of debris remaining, he added, “If its just soil, it will take around 24 hours…If there are rocks, then it could take them 32 hours or even more.”

Another Jhansi resident Vipin Rajput said he has been doing this job for last two-three years. “We are quite confident about our skills that we can easily remove 10-12 metres of debris,” he added.

A part of the 4.5-km-long tunnel being built between Silkyara and Barkot on the Brahmakhal-Yamunotri National Highway — part of the Char Dham all-weather road project — caved in around 5.30 am on November 12 following a landslide, trapping 41 workers from various parts of the country. The collapsed section is 270 metres from the mouth of the tunnel from the Silkyara side.

Mahmood Ahmad, managing director of the NHIDCL, the firm constructing the tunnel, said the miners are trained in working in every situation. “We are hopeful they would be able to drill manually and reach the workers,” he said.

However, bad weather could complicate the rescue operation. The India Meteorological Department (IMD) has predicted thunderstorms, hail and rain in the region, which can lower the minimum temperatures to below 9 degrees Celsius, making the operation tough.

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