A series of closely spaced parallel or nearly parallel faults. CTD
A fold upon which minor folds with similar axis have developed.
Syn:composite fold
See:compound vein
A shaft in which the upper stage is often a vertical shaft, while the
lower stage, or stages, may be inclined and driven in the deposit. In this
type of shaft, underground winding engines are installed to deal with the
lower stages, with transfer points and ore bins at the junction of two
stages. Sinclair, 5
In crystallography, individual crystals of one group united according to
different laws. Standard, 2
a. A vein or lode consisting of a number of parallel fissures united by
cross fissures, usually diagonally.
b. A vein composed of several minerals. Syn:compound lode
a. An arrangement of a number of major ventilation systems serving various
large working areas and served by more than two shafts and their
associated fans, but integrated to form one ventilation system. Usually
adopted in large combined mines. See also:radial ventilation
BS, 8
b. Ventilation by means of a number of splits, which is now normal
practice. See also:ventilation
Air compressed in volume and transmitted through pipes for use as motive
power for underground machines. Compressed air is costly to transmit long
distances, but has certain advantages, namely, it cools the air at the
working face and is relatively safe in gassy mines.
See also:air-conditioning process
A method originated in the United States for breaking down coal by
compressed air. Air at a pressure of 10,000 to 12,000 psi (69 to 83 MPa)
is conveyed in a steel pipe to a tube- or shell-inserted shothole. The air
is admitted by opening a shooting valve and is released in the hole by the
rupture of a shear pin or disk. The sudden expansion of the air in the
confined hole breaks down the coal. Syn:Armstrong air breaker
See also:Airdox
These lamps are self-contained units and comprise a strong alloy casing
within which are a compressed-air turbine and a small alternating-current
generator with stationary windings and revolving field magnets. The air
enters the casing at one side, passes through a filter and then through a
reducing valve that maintains a constant pressure of 40 psi (276 kPa) on
the turbine blades. The air escaping from the turbine is used to scavenge
the inside of the lamp and remove any combustible gases that might have
entered when the lamp was not in use. It is finally discharged through a
series of holes of such a size that the pressure inside the lamp casing is
2 to 3 psi (14 to 21 kPa) above atmospheric. Should this pressure be lost
due to the lamp glass being broken, the light is extinguished
automatically by a spring-loaded diaphragm, which short-circuits the
generator unless held open by the excess pressure. Also called air
turbolamp. Mason
A mine locomotive driven by compressed air. It is very safe and is much
used in gassy mines in Europe. The air is brought down by pipeline from
the surface to a charging station near the pit bottom.
See also:locomotive haulage
Turbines used for driving coal cutters, belt conveyors, and similar
duties. They are not so efficient in their use of the air as piston
engines, but possess the merits of extreme simplicity and robustness, and
therefore are preferred for coal face use. Mason
Blasting powders manufactured in cartridge form for use in small diameter
shotholes. These pellets are particularly useful for horizontal shotholes.
McAdam, 2
A system of forces or stresses that tends to decrease the volume or to
shorten a substance, or the change of volume produced by such a system of
forces. AGI
a. A traveling disturbance in an elastic medium characterized by volume
changes (and hence density changes) and by particle motion in the
direction of travel of the wave. AGI
b. A longitudinal wave (as a sound wave) propagated by the elastic
compression of the medium. Syn:irrotational wave; pressure wave;
P wave. Webster 3rd
The ratio of the volume of space above a piston at the bottom of its
stroke to the volume above the piston at the top of its stroke.
Nichols, 1
That condition in sedimentation in which the flocs or particles are
conceived to be in close contact, further subsidence occurring as a direct
effect of compression resulting in the elimination of water from the flocs
and interstitial spaces. The settling velocity decreases with time of
settling. Mitchell
The surface area affected by compressive strain. CF:neutral zone;
tension zone. Nelson
a. The maximum compressive stress that can be applied to a material, such
as a rock, under given conditions, before failure occurs. AGI
b. The load per unit area at which an unconfined prismatic or cylindrical
specimen of soil will fail in a simple compression test.
Syn:unconfined compressive strength
A stress that tends to push together the material on sides of a real or
imaginary plane. CF:tensile stress
a. A machine, steam or electrically driven, for compressing air for power
purposes. Small air compressors may be compound steam and double-stage
air. Large compressors may be triple-expansion steam and three-stage air
and are always used with condensers. Nelson
b. Any kind of reciprocating, rotary, or centrifugal pump for raising the
pressure of a gas. CTD
c. A machine that compresses air. Nichols, 1