Drops of 12 in (30.5 cm) or more in a line of sluices that are formed by
allowing the discharge end of one box to rest on the head of the
succeeding sluice, instead of telescoping into it. This method ensures a
drop of 12 in or more (depending on the depth of the sluice box) at the
end of each sluice, which usually is sufficient to disintegrate fairly
stiff clay. Griffith
A monkey shaft down which earth and other matter are lowered by means of a
drop (that is, a kind of pulley with brake attached); the empty bucket is
brought up as the full one is lowered. See also:cofferdam
This sinking system consists in the use of a cutting shoe on the bottom of
a shaft lining that is being continually augmented as the shoe descends,
the material inside the lining being excavated. Sinclair, 2
N. of Eng. A door, made of canvas, by which the ventilating current is
regulated and directed through the workings. See also:curtain
Fay
Eng. An interior shaft, connecting an upper and lower seam, through which
coal is raised or lowered. Fay
a. An oversized clast in laminated sediment that depresses the underlying
laminae and may be covered by "draped" laminae. Most dropstones originate
through "ice-rafting"; other sources are floating tree roots and kelp
holdfasts.
b. A stalagmatitic variety of calcite. CF:dripstone
Granulated material obtained by pouring the melted material into water.
Standard, 2
Steel joists hinged to a substantial cross joist in the roof that are held
up by a stirrup during normal running. If a tram runs away down the
incline, the stirrup is disengaged by means of a wire operated from the
top of the incline; one end of the hinged joist falls into the rail track
and arrests the runaway. Mason
Openings connecting parallel passages that lie at different levels.
AGI
A method of breaking oversize stones after primary blasting at a quarry.
See also:drop ball
a. The scum that forms on the surface of molten metals largely because of
oxidation, but sometimes because of the rising of impurities to the
surface, and which contains metal and metal oxides. ASM, 1
b. Small coal that is inferior or worthless and often mixed with dirt.
Nelson
c. Refuse or impurity formed in melted metal. A zinc-iron alloy forming in
a bath of molten zinc while galvanizing iron. Standard, 2
Pile of refuse from a washer. Zern
Flooded; said of mines underwater.
a. A level that is underwater. See also:blind level
b. Part of a drainage drift that, being below both discharge and entry
levels, is constantly full of water. Also called inverted siphon.
BS, 10
Old workings full of water.
A soil and rock failure criterion, which accounts for the general effect
of all three principle stresses by using the invariant of the stress
tensor. Use is limited to numerical formulations, such as finite element
analysis. Desai
One of the large sandstone blocks formerly scattered on the English chalk
downs and used in Stonehenge and other Druid temples and circles.
Syn:sarsen stone
a. The large cylinder or cone on which the rope is coiled when hoisting a
load up a shaft. CTD
b. A metal cask, for shipment of material, having a liquid capacity of 55
gal (208 L). See also:barrel
c. In a conical mill, the cylindrical central section. Pryor, 3
d. A general term for a roller around which a belt conveyor is lapped. It
may be a driving, jib, loop, tension, or holding-down drum. Nelson
e. The spoollike part of a hoisting mechanism on which the cable or wire
line is wound. Long
f. A cylindrical or polygonal rim type of wheel around which cable, chain,
belt, or other linkage may be wrapped. A drum may be driven or driving.
The face may be smooth, grooved, fluted, or flanged.
Balance rope direct from drum drive. Hammond
See:curb
See:roll feeder