In the end, it took only about six weeks to do what mine safety experts say is a job with little precedent: drilling a precision shaft, wide enough to accommodate a man, to a spot more than 2,000 feet — almost half a mile — underground.
“We have a number of mines that are this deep,” said John E Urosek, chief of mine emergency operations for the United States Mine Safety and Health Administration. “But we’ve never had a situation where we’ve had to rescue someone through a bore hole this deep.”
One reason Chilean officials may have thought the drilling could take far longer was that they were not familiar with the type of drill that carved the rescue hole. Three efforts to bore through the abrasive volcanic rock went forward simultaneously — known as Plans A, B, and C — but it was Plan B that broke through to the miners first.
“To tell you the truth, I don’t think anyone had a whole lot of faith in us,” said Brandon Fisher, president of Center Rock, a company in Berlin, that supplied the Plan B drills. “They didn’t understand the technology.”
Fisher and others lobbied the Chilean government to let them use the drills, known as downhole hammers, which have air-powered bits that pound the rock as the drill rotates. The other two drilling operations used more conventional bits that work through rotation only.
Geology
The geology of the region — hard volcanic rock infused with other extremely hard minerals — favoured the Plan B equipment, said Maurice B Dusseault, a professor of engineering geology at the University of Waterloo in Canada. “In very hard, brittle rocks, percussion drilling is indeed an excellent way” to make progress, he said.
The effort was also aided by the dry conditions encountered underground in the Atacama region of Chile, one of the driest deserts in the world. “You can’t do percussion drilling if you have water or mud in the bore hole,” Dusseault said, as the liquids absorb too much of the percussive energy.
But how did they survive the ordeal?
After more than two months trapped in a collapsed Andean mine, the first of 33 Chilean miners were pulled to safety on Wednesday up an escape shaft barely wider than a man’s shoulders. With ingenuity and cutting-edge technology, the men have survived 68 days some 625 metres underground fending off hunger, anxiety and illness in a record-setting feat of survival.
What did they eat?
From the Aug 5 cave-in until they established contact with the surface 17 days later, the miners rationed themselves to two spoonfuls of tuna, half a cookie and a half-full glass of milk every 48 hours.
Once rescuers on the surface discovered the men with a narrow perforation drill, they began sending them hydration gel, soup and medication in narrow plastic tubes called “doves”.
Later, doctors transitioned the men to a solid diet including meat and rice, with a strict 2,200 calorie diet to keep them slim enough to fit in the evacuation shaft just two feet in diameter. In the tunnel near the shelter where the men initially took refuge, they set up a chemical toilet and latrines, along with a duct providing potable water.
Communication
The first sign of life from the miners came on Aug 22, when knocking was heard on a drill head as it reached the depths of the mine. Rescuers withdrew the drill to find a note attached reading, “The 33 of us in the shelter are well.”
Once the first bore hole established a lifeline to the men, letters began to pass between loved ones via the doves. Later came a fibre optic line enabling phone calls and videoconferencing.
Routine underneath
Once they were discovered, the men quickly established a regular meal schedule including breakfast, lunch, dinner and an afternoon tea. Supported by a 500 watt power line, they installed lights to simulate day and night to diminish the impact of their eventual return to the surface. Physiologists set up obligatory exercise schedules to keep the men fit for their trying passage up the escape shaft, when they may have to hold the same posture for as much as an hour.
In recent weeks, the miners began to help with the drilling process, taking shifts to clear away debris that fell into the tunnel of the mine.
Entertainment
Several of the men are football fanatics and one has even played professionally, so despite their isolation they managed to install a live feed of games like Chile’s friendly match against Ukraine to watch using a small projector.
They have also received videos of football greats like Pele and Maradona and set up an area of their refuge for a small “casino” where they play cards, dominoes and dice games. The miners have also received small music players and speakers as well as Bibles and rosaries blessed by Pope Benedict.
Reuters
