|
Hard rock mining is a kind of
underground
mining. With this kind, an opening is made that is called
an
adit. Tunnels into the ground are dug, blasted with
dynamite, or drilled out. These tunnels are called
shafts.
Shafts are dug straight down [vertically] into the ground.
Each shaft has a purpose. One shaft might be for miners to
use to go in and out of the mine. One shaft might be just
for mine machinery. Another shaft is used for air or
ventilation.
When miners get to the bottom of the shafts, there is another
tunnel that leads to the rocks or minerals. In pictures,
this tunnel always looks horizontal but it doesn't have to be.
Tunnels can be slanted or sloped. When we thought of the
inside of a mine, we thought about all of the diagrams that we
had seen. They make it look like a few shafts and a
horizontal tunnel at the bottom. That isn't really the
whole picture. You might say that mines are like an
underground building. You go down in the shaft, and reach
floor number one. There can be other floors under floor
one. For example, we went to a
zinc mine. There was
something called a 'man cage' that was a seat on an inclined
machine. Click on the picture on the right to see a larger
one. The miner would sit on this and travel between 'floors' of
the mine. The man cage travels 800 feet per minute.
There were lots of floors under the floor we were on. They
weren't open anymore and were filled with water. We were
told that there is so much water down there that if there was a
drought, the town
wouldn't have to worry about water at all.
|
 |
The tunnels in a hard rock mine are divided into rooms
with rock pillars. In the picture on the left, the
pillars are colored black. When we visited the
coal mine, these pillars were made of coal. With
the room and pillar way of mining, the miner has more
than one way to escape if he has to.
When the mine owners and the engineers decide that they
will stop taking coal from the mine, they do something
called "robbing the pillars." This means that as
they back out of the tunnels, they take the coal out of
the pillars that hold up the roof. This means that
the roof doesn't have support anymore so it caves in.
This is done very carefully and they get lots of coal
out of the pillars before they leave. |
Hard rock mining is one of the most dangerous kinds of
mining. In the first place, it is underground. It
can be very deep underground. Some mines [like coal ones]
have deadly gases in them. Miners have to always be ready
for cave-ins, explosions, and gases. This is a very hard
and dangerous job. |
