Geology Reference
In-Depth Information
2.2. Underground Coal Mining
Drift mine opening into an underground
mine complex in the Jharia Coalfield, state
of Jharkhand, India.
Photo by Stanley R. Michalski, 1994.
Underground Mining
U
nderground coal mining is comprised of two basic systems; the conventional mining system and the continuous
mining system. Conventional deep mining is a systematic procedure whereby the coal, through a series of
sequential events, is drilled, blasted, excavated, and hauled from the mine. Intermediate steps include rock dusting
for health and safety reasons and roof bolting for insuring roof support in mines. In past mining practice, manual
labor was used to achieve these ends. Modern mechanization has increased productivity by mechanizing the
sequential utilization of machines to perform these operations. In the modern conventional mine, individual
machines are used at the working face to undercutting the coal face, drill the blast holes into the coal seam, load
and haul the coal from the mine, and bolt the roof (Schmidt, 1979, p. 164).
The continuous mining system differs from the conventional system by eliminating the need for the sequential
steps of drilling, blasting, and manually loading coal from the working face. These operations have been optimized
by replacing manual methods with mechanized, mining machines.
Conventional and continuous mining systems continue to be used in various types of underground mining. These
two systems of underground mining account for about 60% of world coal production (World Coal Institute, 2005).
Today
s modern underground mines are extensions or variations of the early drift and bell pit mines. Regardless of
whether they are drift, slope, or vertical shaft mines or use the conventional or continuous mining system, the
development of an underground mine employs either the
'
“
room-and-pillar
”
method, also known as
“
board-and-
pillar
mining or the longwall-mining method. Variations of the two principal mining methods exist in the industry.
For example, room-and-pillar mine development in horizontal bituminous coal seams is quite different from the
room-and-pillar method used to mine steeply pitching anthracite coal seams. Room-and-pillar mining had been the
mainstay of underground mining in the United States whereas the longwall method had been well established in
Europe. Reasons for this difference include shallower seams in the United States and deeper seams in Europe. In
the case of the deeper seams, the required pillar support of the room-and-pillar mining method would leave too
much coal in the ground. Less pillar support would result in the crushing of pillars under the weight of the
overburden. In the 1970s longwall mining in the United States began to rapidly gain acceptance as a mining
method of choice when conditions favor its use (Energy Information Administration, 2008).
”
