New Delhi — For 16 days, authorities in India have tried several approaches to rescuing 41 construction workers trapped in a partially collapsed highway tunnel in the Himalayas, but on Monday, the workers remained right where they have been. The frustrating rescue efforts, beset by the technical challenges of working in an unstable hillside, were turning decidedly away from big machines Monday and toward a much more basic method: human hands.

On Friday, rescuers claimed there were just a few more yards of debris left to bore through between them and the trapped men. But the huge machine boring a hole to insert a wide pipe horizontally through the debris pile, through which it was hoped the men could crawl out, broke, and it had to be removed.

Since then, rescuers have tried various strategies to access the section of tunnel where the men are trapped, boring both horizontally and vertically toward them, but failing.

The 41 workers have been awaiting rescue since Nov. 12, when part of the under-constructin highway tunnel in the Indian Himalayan state of Uttarakhand collapsed due to a suspected landslide.

A small pipe was drilled into the tunnel on the first day of the collapse, enabling rescuers to provide the workers with sufficient oxygen, food and medicine. Last week, they then managed to force a slightly wider pipe in through the rubble, which meant hot meals and a medical endoscopic camera could be sent through, offering the world a first look at the trapped men inside.

But since then, the rescue efforts have been largely disappointing — especially for the families of the trapped men, many of whom have been waiting at the site of the collapse for more than two weeks.

New rescue plan: Rat-hole mining

As of Monday, the rescuers had decided to try two new strategies in tandem: One will be an attempt to drill vertically into the tunnel from the top of the hill under which the tunnel was being constructed.

The rescuers will have to drill more than 280 feet straight down — about twice the distance the horizontal route through the debris pile would need to cover. That was expected to take at least four more days to reach its target, if everything goes to plan, according to officials with the National Highways and Infrastructure Development Corporation.

The second effort will be a resumption of the horizontal drilling through the mountain of debris — but manually this time, not using the heavy machinery that has failed thus far.

A team of six will go inside the roughly two-and-a-half-foot pipe already thrust into the debris pile to remove the remaining rock and soil manually with hand tools — a technique known as rat-hole mining, which is still common in coal mining in India.

Senior local official Abhishek Ruhela told the AFP news agency Monday, that after the broken drilling machinery is cleared from the pipe, "Indian Army engineering battalion personnel, along with other rescue officers, are preparing to do rat-hole mining."

"It is a challenging operation," one of the rat-hole miners involved in the effort was quoted as saying by an India's ANI news agency. "We will try our best to complete the drilling process as soon as possible."

Last week, in the wake of the Uttarakhand tunnel collapse, India's federal government ordered a safety audit of more than two dozen tunnels being built by the country's highway authority.

In:
• India
• Rescue
• Himalayas