As 41 construction workers still remain trapped in the Sikyara tunnel in the northern Indian state of Uttarakhand, the rescuers are now preparing to use the ‘rat-hole mining’ technique in order to create an escape passage. Rat hole mining technique is often found to be employed in Meghalaya, the Northeast Indian state. In this technique, holes are drilled in order to mine coal in small quantities.
Trenchless Engineering Services Private Limited and Navayuga Engineers Private Limited have called more than 10 experts for the application of the rat-hole mining technique in a horizontal manner in the collapsed part.
“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 as quoted by Business Standard.
In addition, the Indian Army has been involved in the rescue work.
Watch | Uttarakhand tunnel rescue: Manual drilling, multiple strategies for tunnel rescue
Just last week, as engineers tried to insert a metal pipe horizontally through the rock, it ran into metal girders. This snapped a huge earth-boring auger machine.
“The broken parts of the auger (drilling) machine stuck inside the tunnel have been removed,” senior local civil servant Abhishek Ruhela told AFP on Monday. A superheated plasma cutter was used to remove the metal.
“Preparations are being made to start manual drilling work,” he added. “Indian Army engineering battalion personnel, along with other rescue officers, are preparing to do rat-hole mining.”
Manual drilling would be a tough task as it will have to be done in a narrow pipe, just wide enough for a crawling man to pass.
“It depends on how the ground behaves,” said Chris Cooper, a tunnel expert who is advising the rescuers. He said that they may have to cut through heavy-duty girders that had been meant to hold the collapsed roof up. “We are confident that we can overcome it”.
A separate effort of vertical drilling is being carried out to reach the men 89 metres below.
“Vertical drilling is going on at a fast pace,” with teams having reached 19 metres (63 feet) by late Sunday, said Mahmood Ahmed, a top official in the national roads ministry.
Work is ongoing at “full speed but with caution”, he added.
The 41 construction workers have been stuck inside the tunnel since November 12. The rescue effort has been slow as several setbacks, like repeated breakdowns of drilling machines, have hampered the work.
(With inputs from agencies)
