The plight of those unfortunate but lucky souls stuck underground but being rescued in Chile reminded me of a historic shaft boring technique I came across in California.
In the 1930s it was used to drive a vertical 1.5m diameter shaft 300m down into the Idaho-Maryland gold mine in Green Valley California.
There were several innovative features:
It was a tubular drill, so only the 50mm wide annulus of rock at the edge of the hole actually had to be cut.
The lump in the middle was simply lifted out of the hole after it had been snapped off at the bottom – a few of these huge rock cylinders are still to be seen on display in the area, and beyond.
There was no long torque shaft.
Instead, power was fed electrically to a down-hole motor/gearbox, and thence by a short shaft to the drill bit.
The whole assembly was lowered from a wooden frame above ground.
Rock was cut by a soft iron blade fed with a constant supply of hard steel granules.
A man stood inside the machine and operated its controls.
My description really has not done the Mr Newsom’s drill justice.
Here is a link to a Popular Science article, which is well worth a look.
Sometimes known as the Round Hole, and also the five foot shaft, it is still in the news because there are plans to re-open the Idaho-Maryland mine and use the hole for ventilation.
I thought the technique might be a quick way to get the Chileans up out of their predicament, particularly as it needs no dangerous blasting.
But, alas, it took almost two years to get 300m.
That said, you only need a 0.6m diameter hole to lift a man through.
And modern diamond cutting edges are much harder than steel granules.
And a larger version of the Newscom drill was later used in Hurley Wisconsin to drill a 300m shaft in seven months.
The photo at the top is cropped from one on the Emgold Mining website.
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