Engineers pave way for mine rescue

Engineers have begun reinforcing an escape shaft drilled 2,050ft through a Chilean mountain to reach 33 trapped miners, paving the way for the group's countdown to freedom to end this Wednesday.

They will lay 16 steel pipes to reinforce 315ft of the hole, a section deemed unstable following a video inspection by geologists and mining experts, before embarking on the nailbiting rescue.

Those in charge of the effort said that they were confident the tunnel is otherwise strong, though there was nervousness at the prospect of something going wrong as the miners are extracted one by one using an escape capsule dubbed "Phoenix", which has spring-loaded wheels to grip the rock as it is pulled to the surface.

"All rescues have their risks. You can never say that an accident couldn't happen," said Laurence Golborne, Chile's mining minister. "This rescue won't be over until the last person below leaves this mine… There are a lot of things to do and we have to make no mistakes."

The miners have been trapped deep in the mountain at the San Jose mine - 500 miles from Santiago, the Chilean capital, in the high Atacama desert - since the rock caved in on 5 August.

The effort to bring them home represents one of the most complex and technically challenging rescue operations in mining history.

Families of the 33 men, who are camped out at the mine, wept, sang and danced for joy on Saturday when the relief shaft broke into the underground cavern where they have been confined. In Santiago, motorists sounded their car horns and spontaneous celebrations broke out across the country. In the depths of the mountainside, the miners cheered and cried.

"You think we were happy, you should have seen those guys," said Gregory Hall, one of the rescue drill operators. "They were just going crazy."

Known as "The 33", the miners range in age from 19 to 63. Food supplies and video links were established through small boreholes cut through the rock.

They will spend their final days being put through tough exercises designed to prepare them mentally and physically for their delicate and nerve-wracking haul to the surface. They have been put on a special diet devised by survival experts at Nasa, the US space agency, including salt supplements and aspirin to protect against high blood pressure and blood clots.

Two of the rescue shafts, known as "Plan A" and "Plan C", stalled when they kept veering off course due to the toughness of the quartzite and silica rock through which the mine's deposits of copper and gold run.

American Jeff Hart, 40, had been working in Afghanistan boring water holes for the US Army when he was called to Chile to lead the Plan B drilling effort.Considered one of the world's best handlers of the T130 drill used in the rescue, he joked that when he felt a "pop" on the drill as it punched through the rock and into the miners' chamber, he thought that it was the sound of his heart stopping. He was feted with hugs, cheers and champagne. "I was nervous… I'm very happy now," he said.

At one point, the drill's hammers were shattered after striking one of the mine's metal support beams unexpectedly, causing several days' delay while magnets were lowered into the shaft to retrieve the pieces and new equipment was flown in from the US.

James Stefanic, operations manager for Geotec, the American-Chilean contractor that handled the job, said that it was the most difficult hole they had ever drilled. "If you're drilling for oil and you lose the hole, it's different. This time, there are people down below," he said.

From the first miner climbing into the escape pod to the last being hauled to the surface is an operation expected to last up to 48 hours.

"It's hard to imagine those who are down there will sleep or be able to rest, given the anticipation. As a result, the last to come up must be pretty strong to be in good enough shape to leave after a long time of waiting," said Mr Golborne.