See:air crossing; overcast.
Comminution of ore to a smaller particle size than is required for
effective liberation of values before concentrating treatment. Opposite of
undergrinding. Pryor, 3
In this method, two level drives are first connected, the lower and upper
one by a raise, from the bottom of which mining is begun. The work
proceeds upwards, filling the mined-out room, but in the filling, chutes
are left through which the broken ore falls. In inclined seams the chutes,
also inclined, have to be timbered. The lower-level drive is protected
either by timbering or vaulting, or by a fairly strong pillar of vein
fillings. Stoping in the different cuts always proceeds upwards, but as a
whole it proceeds between the two level drives in a horizontal direction.
Overhand cut-and-fill, esp. in mining irregular orebodies of greater size,
is also called back stoping. Stoces
a. Stope in which the ore above the point of entry to the stope is
attacked, so that severed ore tends to gravitate toward discharge chutes
and the stope is self-draining. Pryor, 3
b. An overhand stope is made by working upward from a level into the ore
above. McKinstry
a. In this method, which is widely used in highly inclined deposits, the
ore is blasted from a series of ascending stepped benches. Both horizontal
and vertical holes may be employed. Horizontal breast holes are usually
more efficient and safer than vertical upper holes, although the latter
are still used in narrow stopes in steeply inclined orebodies.
McAdam, 2
b. The working of a block of ore from a lower level to a level above. In a
restricted way overhand stoping can be applied to open or waste-filled
stopes that are excavated in a series of horizontal slices either
sequentially or simultaneously from the bottom of a block to its top.
Stull timbering or the use of pillars characterize the method. Filling is
used in many instances. Modifications are known as backfilling method;
back stoping; block system; block system of stoping and filling; breast
stoping; combined side and longwall stoping; crosscut method of working;
cross stoping; Delprat method; drywall method; filling system; filling-up
method; flatback stoping; longwall stoping; open cut system; open stope
and filling; open-stope method; open-stope, timbering with pigsties, and
filling; overhand stoping on waste; resuing; rock filling; room-and-pillar
with waste filling; sawtooth back stoping; side stoping;
slicing-and-filling system; stoping and filling; stoping in horizontal
layers; transverse with filling. Syn:combined side and longwall stoping;
Delprat method; overbreaking. CF:back-filling system; chimney work;
underhand stoping.
overhand stoping and milling system
See:combined overhand and underhand stoping
See:overhand stoping
overhand stoping with shrinkage and delayed filling
a. Cliff overhang. AGI
b. A part of the mass of a salt dome that projects out from the top of the
dome much like the cap of a mushroom. AGI
a. Describes a condition when a journey travels towards a haulage engine
at a faster rate than the rope, which then becomes slack and liable to
foul the drum. Also called overrun. Nelson
b. The transportation of excavated material beyond certain specified
limits. Seelye, 1
c. In many highway contracts, a movement of dirt far enough so that
payment, in addition to excavation pay, is made for its haulage.
Nichols, 1
d. Applied to inspection, cleaning, and repairing of machines or plant.
Nelson
A type of equipment for the removal of soil or rock. It consists of a
strong overhead cable, usually attached to towers at either end, on which
a car or traveler may run back and forth. From this car a pan or bucket
may be lowered to the surface, subsequently raised and locked to the car,
and transported to any position on the cable where it is desired to dump
its contents.
See:trolley conveyor
This system is popular for use in mines since it can be suspended from the
roadway supports as the face advances and can carry supplies over
equipment installed in the roadway; transport is by means of endless,
main-and-tail, or main-rope winches. They are generally slow-moving and
can carry light loads into and around many places inaccessible to other
forms of transport. See also:monorail
In this system, the loads are carried by bogies running on a taut wire
rope instead of steel joists or flat-bottomed rails. See also:monorail
Sinclair, 3
See:aerial ropeway
A tractor loader that digs at one end, swings the bucket overhead, and
dumps at the other end. Nichols, 1
A crane that traverses the whole width of a workshop along the rails on
which it runs. Hammond
See:trolley conveyor
a. A general term referring to the extension of marine, lacustrine, or
terrestrial strata beyond underlying rocks whose edges are thereby
concealed or overlapped, and to the unconformity that commonly accompanies
such a relation; esp. the relationship among conformable strata such that
each successively younger stratum extends beyond the boundaries of the
stratum lying immediately beneath. CF:onlap
b. The area common to two successive aerial or space photographs or images
along the same flight strip, expressed as a percentage of the photo area.
AGI
c. The portion of a borehole that must be redrilled after caving of the
hole, cementing a section of the hole, or bypassing unrecoverable
material. Long
d. A reversed fault or thrust. BS, 11
e. The lineal portion of a branch hole that nearly parallels the parent
hole. Long
To combine the forcing and exhausting systems, it is not necessary to
provide two ducts, one forcing and one exhausting, throughout the length
of the heading. An arrangement that serves the same purpose is the overlap
system. In this system a main exhausting duct is used within a convenient
distance of the face, often about 100 ft (30.5 m). Some of the intake air
in the heading, before reaching the end of this duct, enters a short
length of tubing and is blown onto the face. The advantages of both
systems are thus obtained. Precautions must be taken against recirculation
of air by the forcing unit, to prevent concentration of dust, and in
collieries, combustible gases, at the face. The two ducts must overlap by
a minimum distance which, in practice, is usually taken as 30 ft (9.1 m).
See also:auxiliary ventilation
Roberts, 1