Underground mining is used when the coal seam lies deep in
the earth. In an underground mine only
some of the coal is removed. The coal
that remains helps support the mine roof. Underground mines look like a system
of tunnels. The tunnels are used for
traveling throughout the mine, moving coal from place to place and allowing air
to circulate in the mine.
The coal that is
mined is put on trolleys pulled by haulage system to the surface.
There are three types of underground mines: slope, drift, and shaft. When the coal seam
is close to the surface but too deep to use surface mining, a slope mine can be
built. In a slope mine a tunnel slants
down from the surface to the coal seam. In a slope mine, the miners and materials ride in special cars
to get to the coal seam
A drift mine is built when the coal seam lies in the side of
a hill or mountain. Drift mines may also
be built in a surface mine that has become too deep. Two types of underground
mining are used: room and pillar mining and longwall mining. Room and pillar mining leaves pillars, or
blocks, of coal in the mine to support the roof. In longwall mining the roof is allowed to
collapse in a planned sequence.
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