Mining for coal

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Mining for coal
Deep Mining
Bell Pits
In early mines a vertical shaft was dig down to the seam which
was then exploited in all directions, giving a "bell shapes" cavity.
These mines would be worked until JUST before the roof
collapsed. Example Forest of Dean. There are many problems
associated with this mining...
Subsidence of area around the bell pit
There may be unmarked shafts, incompletely filled in and liable to collapse
Rock left after the mining may be unstable and permeable
There are pockets of methane gas and air needed for the methane to combust
There may be cavities full of water which can flood other workings if broken
Pillar and Stall
When mining became more organised and on a larger
scale, new mines were created that were deeper and
larger, these mines tried to stop subsidence. 3 metre wide sectiopns of the coal seam
the pillar would be left in place (waste of coal) to support the roof rock, while the coal
around it was worked away, leaving and empty space or stall. The problems associated
with this mining
Coal does not have a high loadbearing strength (it has horizontal bedding and
In many cases, too much coal is taken, leaving pillars which were too thin to
support the load
The pattern of pillars was often haphazard (no optimum arrangement to give the
greatest support)
Sooner or later, subsidence occurs.
Abandoned working can fill with water or methane gas, a hazard for future

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Longwall mining
A more economical system is to extract the whole coal
seam, this is made possible by specially designed
machinery, once the coal has been removed the space is
left behind to sink, but as the subsidence is uniform it
does not adversely affect the surface.…read more

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Time Long term Short term
Developmen Costly shafts and roadways Quick
Afterwards No impact if pithead is cleared Reclaimed for farmland
Cost More expensive, but larger Cheaper to develop and operate
reserves of coal…read more


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