A quarry in which the walls slant outward (overhang the working face) so
as to make the floorspace wider with increasing depth. Fay
a. In salt mining, an electrically driven machine somewhat like a gigantic
chain saw. It has a long, thin horizontal bar, about which revolves an
endless chain with cutting bits. The most common type is an adaptation of
the shortwall coal cutter, a drag-type machine with continuous pick-filled
chains to cut at the floor or bottom of the seam. It can make a rapid,
continuous cut across the entire width of the face. Kaufmann
b. See:machineman
a. The process of cutting under the face of a coal seam with a machine so
the coal can be shot down readily.
b. A quarrying method intermediate between open pit and adit. Channel
cuts, or separations made by wire saws or other means along the quarry
walls, are slanted outward; thus, the floorspace is enlarged gradually.
Wings or buttresses of stone may be left at intervals for wall support.
c. The making of a cut, by hand or coal cutter, along the floor level in a
coal seam to ease its working by hand or breaking by explosive.
See also:undercut; floor cut; holing. Nelson
An electrically driven machine used to make a cut about 10 ft (3.0 m) deep
near the bottom of a coalbed. Hudson
A method of mining a vein that has been worked out above and in which the
shaft is further sunk, with a crosscut being made to the vein at a depth
below the previous workings. Stoces
Drilling below the theoretical blasting bottom. Syn:subdrilling
A hard fireclay forming the floor of a coal seam. See:underclay
AGI
The material that forms the floor of an ironstone mine. Nelson
To advance a diamond or other type of rock-drilling bit into rock at a
lesser rate than that warranted by the condition of the rock and/or the
condition of the bit. Long
A mechanical stoker suitable for small boilers, such as the vertical,
water-tube, and locomotive types. Coal is conveyed direct from a bunker or
hopper by a feed worm, which forces the fuel up through the bottom of the
retort in which it is burned. Volatiles driven off must pass through the
ignited fuel, thus eliminating smoke. An underfeed stoker operates most
successfully on graded coals with an upper size limit of 1 to 2 in (2.5 to
5.1 cm). See also:stoker; vibrating grate. Nelson
a. In ceramics, to fire (as brick) insufficiently. Webster 3rd
b. To fire from beneath. Webster 3rd
The oversize material leaving a classifier. Nelson
a. Arrangements, such as high-capacity supplementary conveyors, staple
pits, hoppers, or standage room for cars, positioned at key points between
the faces and pit bottom. The object is to enable costly power-loading
machines to operate continuously when there are surface or shaft delays.
See also:bunker conveyor; gate road bunker. Nelson
b. A large-capacity hopper to absorb peak deliveries and provide an even
rate of feed to main transport systems, or winding shaft.
See also:bunker
A single or multiple conductor cable sheathed in lead or other waterproof
materials, carried in a duct beneath the surface of the ground.
Crispin
Mines or areas that are connected underground shall be considered as a
single mine if the underground connections between previously separate
mines or areas subject the workers in the respective mines or areas to a
reasonable likelihood of danger from mine fires or the products of fires,
explosions or the forces and products of explosions, mine inundations, or
personnel accidents.
Seal against water or spread of fire. Pryor, 3
a. The driving of advance exploring headings and up-and-down boring to
establish the continuity and thickness of coal seams or other mineral
deposits. See also:exploratory drilling
b. Extensions of a known ore deposit may be probed along its strike or dip
in which shafts, drifts, or crosscuts may be driven. A study of the habits
of known ore shoots, by mapping, surveying, and sampling, is a desirable
preliminary to underground exploration. Nelson
There are two types of underground fires: (1) those that involve exposed
surfaces and are known as open, freely burning fires and (2) those that
may be wholly or partly concealed and are invariably caused by spontaneous
heating of the coal itself, known as gob fires. Mason
A method of burning the coal in place to produce a combustible gas that
can be burned to generate power or processed into chemicals and fuels. Air
and/or steam is blown underground to support the controlled combustion in
the coal seam. The resultant gaseous mixture is a low-heating-value fuel
gas. See also:blind borehole process
Syn:underground coal gasification