a. A borehole, the course of which has deviated or departed from the
intended direction or did not reach its intended target. Long
b. Inward-bulged casing that has been straightened by the use of a drift.
See also:drift
c. A horizontal underground passage parallel to or along a vein or related
structure. Long
See:glacial epoch
a. An air-driven, percussive rock drill; also called leyner; liner.
Long
b. A drill crewman, miner, or laborer who travels from place to place,
only working a short period of time at each place. CF:boomer
Long
c. A person skilled in the use of air-driven, percussive rock drills and
other processes utilized in excavating horizontal underground passages or
tunnels. Long
d. An excavator of mine drifts. Webster 3rd
See:bar; drill column.
The heaviest form of hammer drill made in various sizes depending upon the
severity of the work to be done. The heaviest type weighs more than 200 lb
(91 kg) and is used for holes up to 20 ft (6.1 m) in depth. Must be
mounted on a column or bar. Lewis
See:square set
Various types of mechanical or photographic devices used to determine the
compass bearing and inclination of the course of a borehole.
CF:clinometer
In bituminous coal mining, one who is engaged in driving a drift, a
horizontal passageway underground following the coal vein in a mine.
DOT
An instrument for determining the inclination of a drill pipe from the
vertical and the depth of measurement. AGI
a. A placer or gravel deposit worked by underground mining methods.
Webster 3rd
b. A mine that opens into a horizontal or practically level seam of coal.
This type of mine is generally the easiest to open as the mine opening
enters into the coal outcrop. Kentucky
c. One opened by a drift. Pryor, 3
a. A term applied to working alluvial deposits by underground methods of
mining. The paystreak, varying from 2 to 8 ft (0.6 to 2.4 m), sometimes
greater, is reached through an adit or a shallow shaft. Wheelbarrows or
small cars may be used for transporting the gravel to a sluice on the
surface. If relatively large, the deposit is removed in a system of
regular cuts or slices taken across the paystreak, working generally in a
retreating fashion from the inner limit of the gravel. Drift mining is
more expensive than sluicing or hydraulicking; consequently it is used
only in rich ground. See also:placer mining
b. The working of relatively shallow coal seams by drifts from the
surface. The drifts are generally inclined and may be driven in rock or in
a seam. Drift mining may be viewed as intermediate between opencast coal
mining and shaft or deep mining. See also:development drift;
surface drift. Nelson
A peat deposit associated with or embedded in glacial drift. Fay
Fluffy, flaky salt particles due to wind and wave action, which produce a
mist over the surface of solar salt ponds. The mist contains minute
particles of salt, which are driven to the lee shore and deposited as a
scale. Kaufmann
A strong timber set in a drift that may form the anchorage for the timber
sets of the stope above. Nelson
Side slicing as a method of stoping massive deposit. Alternative to top
slicing. Pryor, 3
The excavation of the development drift together with the stope in
overhand stoping. Employed in cases where the hanging wall is strong.
Nelson
See:sublevel stoping
That theory of the origin of coal that holds that the plant matter
constituting coal was washed from its original place of growth and
deposited in another locality where coalification then came about.
See also:allochthonous coal
See:dry ice
a. Any cutting tool or form of apparatus using energy in any one of
several forms to produce a circular hole in rock, metal, wood, or other
material. See also:calyx drill; churn drill; core drill; diamond drill;
rock drill; rotary drill; shot drill. Long
b. To make a circular hole with a drill or cutting tool. Long
a. The relative speed at which a material may be penetrated by a drill
bit. High drillability denotes easy penetration at a fast rate.
Long
b. The specific value of the drilling properties of a rock expressed in
terms of the drilling rate under certain technical conditions.
Fraenkel