Cracks developing from the upper or tension side of a stratum caused by
bending moment over a coal seam. Such breaks are induced in the nether
roof in consequence of the moment exercised by the weight of the
roof-stratum overhanging the face, cantilever fashion. The weight break
differs from a shear plane in the more ragged and uneven character of the
fracture and in hanging over the waste instead of over the unmined coal
seam. Also called first break. Briggs
A seismic technique by which energy can be sent downward into the ground
without the necessity of drilling shotholes. This technique involves
lifting a weight, then permitting it to fall and strike the ground. The
waves from the impact are then recorded. In areas where drilling is
difficult, otherwise undesirable, or unduly expensive, this technique may
be highly advantageous. Dobrin
Value calculated from a number of samples, each of which has been assigned
an importance in accord with its position and general trustworthiness. In
this connection a sample which was cross-checked by others would be more
reliable than one which was isolated, particularly if the latter showed
abnormal values or was for any other reason suspect. The cross-checked
sample is sometimes called a weighted sample in mineral valuation of a
deposit. Pryor, 3
A method of comparing the average depth of mine workings. It is based on
the average depth from which the output is obtained, weighted for the
tonnage produced. Nelson
A materials flowsheet including a statement of the capacity in tons per
hour at principal points in the plant. BS, 5
An apparatus for recording and indicating the tension on a drilling line
of a diamond or rotary drill. See also:tension drilling
The occurrence of fracturing of the upper roof, with consequent rapid
increase of the weight carried on the timber and packs supporting the
roof; distinct from the fracturing of the nether roof. TIME
An appliance for the continuous weighing of coal or other material in
transit on a belt conveyor. See also:weighing-in-motion system
Nelson
The pit below the shaft station where heavy weights are attached to the
guide ropes to keep them taut. Roughly, the weight needed is 1 st for each
1,000 ft (1.97 t per 1,000 m) of rope. Higham
The strength of an explosive per unit weight, expressed as a percentage of
the value for blasting gelatin as a standard.
See also:absolute weight strength
Square type of machine in which air is blown down to join pulp entering
the cell below a mechanically driven impeller. Pryor, 3
a. A small dam in a stream, designed to raise the water level or to divert
its flow through a desired channel. AGI
b. A notch in a levee, dam, embankment, or other barrier across or
bordering a stream, through which the flow of water is regulated.
AGI
The depth of water in a measuring weir as measured from the bottom of the
notch to the surface of the water upstream of the weir. The velocity of
approach is not included. Hammond
A device to estimate the quantity of water that flows during a given time
over a weir of a given width at different heights of water. Fay
a. A configuration used in the surveying of a mine shaft. Pryor, 3
b. The highly attenuated triangle formed by the plan position of two shaft
plumblines and one observation station. BS, 7
An isometric(?) mineral, Cu5 Te3 ; bluish-black; at Vulcan,
CO.
The quadrilateral formed by the plane position of two shaft plumblines and
two observation stations. BS, 7
A term applied to pegmatitic and aplitic dikes, the boundaries of which
have been obliterated by continued growth of the minerals of the granite
into which the dikes have been injected. Holmes, 2
A glass-rich pyroclastic rock that has been indurated by the welding
together of its glass shards under the combined action of the heat
retained by particles, the weight of overlying material, and hot gases. It
is generally composed of silicic pyroclasts and appears banded or streaky.
Syn:tuff lava
A base or frame made of pieces welded together, as contrasted with a
one-piece casting or a bolted or riveted assembly. Nichols, 1
See:Weldon process