Uttarkashi: Rat hole mining is the traditional technique that rescuers have resorted to in order to free the 41 workers who have been stuck there for the past 15 days after heavy machinery, such as the American auger, failed to drill through the debris to provide an escape route for them.
Rat-hole mining is often associated with Meghalaya, where holes are drilled for mining small amounts of coal.
At the Silkyara tunnel in Uttarkashi, at least 12 experts have been called by Trenchless Engineering Services Private Limited and Navayuga Engineers Private Limited to apply the rat-hole mining technique horizontally in the collapsed part of the main structure.
They have come from Delhi, Jhansi and other parts of the country.
"They will have to drill at least 10 to 12 metres with their own hands. They will mostly use two tools -- hand-held drilling machines to remove the rubble and gas cutters for cutting the iron hurdles," an official said.
According to Neeraj Khairwal, Additional Secretary, Uttarakhand government and the state nodal officer for the rescue operation, a skilled team of workers called to apply the rat-hole mining technique will remove the rubble with their hands.
"As they remove the muck, the tunnel pipe (800-mm) will be pushed gradually by the machine through the rubble," Khairwal said.
"We will do the drilling and collect the muck with our hands. We have been doing this for years," one of the workers, Mohan Rai said.
He said they will be in proper gear, wearing oxygen masks and glasses to cover their eyes.
"We can remove five-six metres of rubble using this method in 24 hours," Rai said.
Rakesh Rajput, another expert, said three of them will go inside the tunnel, one will do the drilling, another will collect the muck and the third one will push the muck through the trolley.
Another expert in the rat-hole mining technique said they can remove 10 metres of muck or rubble in 20 hours.
With PTI inputs