D E F
W X Y
Reclamation - The costs incurred
to restore land to its original (or better) condition.
Rock Dusting - The dusting of underground areas
with powdered limestone to dilute the coal dust in the mine atmosphere
thereby reducing explosion hazards.
Roll - Used to describe minor deformations or
dislocations of a coal seam, for example, faults with small displacement
to small monoclinal folds, to welts or ridges projecting from
either the roof or floor into the coal, and to fillings of stream
channels or low areas extending downward into the coal.
Roof Bolting (Pinning) - A system of roof support
in mines. Boreholes from 3 to 8 feet long are drilled upward in
the roof and bolts of 1 inch diameter or more are inserted into
the holes and anchored at the top by a split cone or similar device.
The bolt end protrudes below roof level and is used to support
roof bars, girders, or simple steel plates pulled tight up to
the roof by a nut on the bolt head. The bolts are put up to a
definite pattern. The idea is to clamp together the several roof
beds to form a composite beam with a strength considerably greater
than the sum of the individual beds acting separately.
Room - A place abutting an entry or airway where
coal has been mined and extending from the entry or airway to
Room and Pillar - A system of mining in which
the distinguishing feature is the winning of 50 percent or more
of the coal or ore in the first working. The coal or ore is mined
in rooms separated by narrow ribs or pillars. The coal or ore
in the pillars is won by subsequent working, which may be likened
to top slicing, in which the roof is caved in successive blocks.
The first working in rooms is an advancing, and the winning of
the rib (pillar) a retreating method. The rooms are driven parallel
with one another, and the room faces may be extended parallel,
at right angles, or at an angle to the dip. This method is applicable
to flat deposits, such as coal, iron ore, lead, zinc, etc., that
occur in bedded deposits.
Rotary Dump - An apparatus for overturning one
or more mine cars simultaneously to discharge coal. They may rotate
either 180 degrees or 360 degrees.
Royalty - A share of the product or profit reserved
by the owner for permitting another to use the property. A lease
by which the owner or lessor grants to the lessee the privilege
of mining and operating the land in consideration of the payment
of a certain stipulated royalty on the mineral produced.
Runoff - That portion of the rainfall that is
not absorbed by the strata; is utilized by vegetation or lost
by evaporation or may find its way into streams as surface flow.