Geology Reference
In-Depth Information
The Special Case of Anthracite Mining
A
lthough anthracite coal mining is of relatively minor importance today, the methods of recovering anthracite coal
include surface mining, room-and-pillar, and longwall mining when the coal beds are relatively flat lying. The
excavation of very deep strip-mining pits (surface mining) and the unique method of steep-pitch mining (under-
ground mining) are used when the anthracite coal seam slopes into the ground at a steep angle. Steep-pitch mining
requires driving gangways perpendicular to the slope of the coal that begin at the base of a slope or shaft mine
entry. The gangways usually contain mine car tracks that are used to haul the mined coal to the slope or shaft,
deliver men and equipment to the working faces, and provide a conduit for ventilating the mine (Rhone, 2008,
p. 3). Gangways are followed by chute-and-pillar mining (a variation of room-and-pillar) upslope of the gangways.
The method allows the mined coal to fall by gravity from the room being mined through a chute and into coal
shuttles that move into and out of the mine along a network of gangways (Otto, 1925, p. 712). The method of
driving gangways and the chute-and-pillar method of steep-pitch mining was highly developed in the anthracite
coal basins of the eastern United States (Buch and Corgan, 1956, p. 44; Otto, 1925, p. 711). The introductory figure
of Section, 2.3 is a photograph of the Centralia Basin, a part of the Western Middle Field of the anthracite coal
fields of the eastern United States where steep-pitch underground mining and surface mining techniques were used
to maximize recovery.
As in most forms of mining, anthracite surface mining methods recover the most coal. Anthracite underground
methods, particularly the room-and-pillar method, result in substantial coal left in the ground. The remaining coal is
in the form of pillars that support the mine or as barrier pillars to control water or separate one mining operation
from another. These remaining pillars also support surface features such as highways, towns, railroads, streams,
and rivers.
Ventilation
P
roper ventilation of active underground workings is an integral part of the conventional and continuous
mining systems. Without it, underground coal mining cannot proceed since the proper movement of air
throughout the mine brings fresh air to the working face so miners can breath. Proper ventilation also carries
away explosive and poisonous gases and prevents the accumulation of heat in areas prone to spontaneous
combustion. Ventilation is accomplished by using the existing tunnels, galleries, cross-cuts, and haulage
ways to create a ventilation circuit. The ventilation circuit is driven by large fans that exhaust the mine air
from the mine while fresh air inflow is directed to the area to be ventilated. The quantity (volume) and
velocity of air flowing through a mine are a function of the rate at which gases are liberated at the working
face (Schmidt, 1979, p. 179). Since the mining operation continuously creates new tunnels and an advancing
working face, the ventilation system becomes dynamic and must constantly change as the mining progresses
and underground conditions change.
