DEHRADUN: With the stubborn rubble of an under-construction tunnel in Uttarkashi knocking an auger machine out of action, rescuers of 41 labourers stuck on the other side of the debris oscillated between expediting vertical drilling and exploring manual horizontal drilling.
In the end, it was decided to exhaust all options for horizontal drilling before initiating the vertical one. “Only equipment for vertical drilling is being placed. Vertical drilling won’t start till we exhaust the first option of 800 mm pipes,” said Col Deepak Patil, head of the rescue operations.
The US auger machine managed to drill about 47 metres horizontally into the rubble in phases and insert 2.7 ft wide pipes into it before the blades of the drill head broke and got stuck in the debris on Friday. “Augering is finished...the auger is broken, destructed,” international tunnelling expert Arnold Dix said in Silkyara.
The width of the rubble is estimated to be 60 metres. Manual drilling involves sending a worker into the 2.7 ft pipe, drilling briefly from within the confined space and exiting so that another labourer can take over. It can begin as soon as the stuck auger drill head is extracted.
A steel chute had been pushed through, in sections, up to this point where the rotary blades were stuck in the horizontal pipe, followed by the long auger. About 20 metres of the auger in the chute has been cut out, Uttarakhand Chief Minister Pushkar Singh Dhami said. A plasma cutter is being airlifted from Hyderabad to tackle the remaining 25 metres.
Dix was confident that the labourers would be eventually rescued. “I have always promised that they will be home by Christmas,” he said.
As for vertical drilling, a 1.5-km access road to the top of the tunnel has already been built by the Border Roads Organisation (BRO).
“The platform for launching the drilling machine with markings of drilling points has also been finalised,” official sources said.
“Vertical drilling is time-consuming and complicated. It demands more exactitude and caution because of the narrow space on the tunnel roof,” said Dix. It would involve 86 metres of burrowing from the top.
Parallelly, work is continuing on a rescue tunnel from the Barkot end of the tunnel, with four explosions already creating a 9.10-metre cavity.
Uttarakhand minister Premchand Agarwal told this newspaper, “A BSNL landline is being provided near the tunnel so that families of the workers can talk to them.” The workers are in a built-up 2 km stretch of the tunnel where there is electricity and water supply. Food and medicines are being delivered through a 6-inch pipe.
READ MORE STORIES ON THE TUNNEL COLLAPSE HERE: