In rock crushers, a deliberate weak link that yields if excessive strain
is developed. May be a scarfed toggle, weak cap bolts on a pitman, a
shearpin in drive, or a clutch designed to fail at a given load.
Pryor, 3
Arkansas. One of a row of props of sufficient strength to cause the rock
above the coal to break and so limit the area of top brought down by a
brushing shot.
Inferior ores arranged ready for crushing. Nelson
See:fracture stress
A fault.
a. The line in which the roof of a coal mine is expected to break.
b. The line of complete extraction of coal.
c. A line roughly following the rear edges of the pillars that are being
drawn or mined. See also:rib line
Providing a crack indication by striking small slits in the longitudinal
direction of a row of drill holes in quarries.
a. To pull drill rods or casings from a borehole and unscrew them at
points where they are joined by threaded couplings to form lengths that
can be stacked in the drill tripod or derrick. Long
b. An accidental flow of metal through a hole in a furnace lining.
A row of timbers erected for the purpose of breaking the roof in pillar
mining. Hess
a. A passage cut through a pillar to allow the ventilating current to pass
from one room to another. Larger than a doghole. Also called room
crosscut. Syn:cut-through; crosscut.
b. The point at which a drill bit leaves the rock and enters either a
natural or a constructed opening. Long
c. An opening made, either accidentally or deliberately, between two
underground workings. Long
d. In an ion-exchange column used in leaching, the arrival of traces of
uranium in the final column during the loading (adsorption) cycle.
Pryor, 3
e. See:stenton
A thrust fault that cuts across one limb of a fold. AGI
a. Eng. An excavation commenced from the bottom of a tunnel heading and
carried upward, so as to form two interior working faces.
b. Mid. To cut away and remove the floor of an entry or other opening.
On exhaustion of an ore deposit or cessation of an exploitation, the value
of its onsite buildings, equipment, stockpiles, untouched remnants of ore
concentrates, etc.; in foundations of plant; and any other assets still
having value apart from their original use. Pryor, 3
An offshore structure (such as a mole, wall, or jetty) that, by breaking
the force of the waves, protects a harbor, anchorage, beach, or shore
area. AGI
a. In a coal mine, a chamber driven in the seam from the gangway, for the
extraction of coal; the face of a working.
b. In Italy, a stall in a steep seam from 12 to 18 yd (11 to 16.5 m) wide.
The stalls are carried one above another from the lowest level to the
rise.
c. Leic. To take down or get a buttock (face) of coal end on.
d. The end, in unmined rock, of an underground excavation, sometimes
called the face; the vertical end surface of a block.
See also:before breast
e. A place where anthracite coal is mined; in the soft coal regions, it is
called a room. BCI
f. The face of a working.
g. That part of the bedplate that is back of the crossheads in engines of
the Corliss type.
h. The side of the hearth containing the taphole in a blast furnace; the
rammed material in which the taphole is installed in a cupola.
Pennsylvania. A system of working anthracite coal by bords 10 yd (9.1 m)
in width, with narrow pillars 5 yd (4.6 m) wide between them, holed
through at certain intervals. The breasts are worked from the dip to the
rise. See also:bord-and-pillar
An auger supported by a breastplate against a miner's body. Used for
drilling holes in soft coal. Fay
a. Planking placed between the last set of timbers and the face of a
gangway or heading which is in quicksand or loose ground.
b. The timber or boards placed horizontally across the face of an
excavation, or heading, to prevent the inflow of gravel or other loose or
flowing material. Stauffer
Scot. A borehole put in parallel with the seam, that is made and kept in
advance of a working place for the purpose of ascertaining the position of
old works, tapping water, letting off gas, etc. Fay
The face of the middle or main layer of coal in a composite seam.
Nelson
A small, portable hand drill customarily used by handsetters to drill the
holes in bit blanks in which diamonds are to be set. The upper end of the
drill is provided with a plate against which the breast of the operator is
pressed to force the bit into the work. CF:brace