Uttarkashi Tunnel rescue: How long rat-hole miners will take to dig remaining 12 metres?

New Delhi: Rescuers have fallen back on the rat-hole mining technique to evacuate 41 labourers trapped in a tunnel in this Uttarakhand district for 15 days, following the failure of a heavy machine to drill through the rubble to create an escape passage for them.

What is rat-hole mining?

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 for applying 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.

How long rat-hole miners will take to dig remaining 12 meters?

"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 hand.

"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 hand. We have been doing this for years," one of the workers, Mohan Rai, told PTI.

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.