Mining_Methods_UnderGround_Mining - Mining and Blasting
Mining_Methods_UnderGround_Mining - Mining and Blasting
Mining_Methods_UnderGround_Mining - Mining and Blasting
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pumphouses <strong>and</strong> workshops. Drill/blast<br />
is the st<strong>and</strong>ard excavation method for<br />
drifting. Firing sequence for a typical<br />
parallel hole pattern is shown to the<br />
right. Note that the contour holes are<br />
fired simultaneously with light explosives,<br />
<strong>and</strong> that the bottom holes, or lifters,<br />
are fired last to shake up the muck<br />
pile for faster mucking.<br />
A deep shaft may secure many years of<br />
production, until ore reserves above the<br />
skip station are exhausted. The shaft can<br />
be rectangular, circular or elliptical in<br />
profile. Extending the shaft in an operating<br />
mine is costly <strong>and</strong> difficult, re-<br />
quiring both expert labour <strong>and</strong> specialized<br />
equipment.<br />
Drifts <strong>and</strong> ramps are dimensioned to<br />
accommodate machines passing through,<br />
or operating inside. Space must include<br />
a reasonable margin for clearance, walk-<br />
ways, ventilation ducts, <strong>and</strong> other facilities.<br />
Cross-sections vary from 2.2 m x<br />
2.5 m in mines with a low degree of<br />
mechanization to 5.5 m x 6.0 m where<br />
heavy equipment is used. Only 5.0 sq m<br />
section is sufficient to operate a railbound<br />
rocker shovel, whereas 25.0 sq m<br />
may be needed for a loaded mine truck,<br />
including ventilation duct.<br />
Normal ramp grades vary between<br />
1:10 <strong>and</strong> 1:7, with the steepest grade to<br />
1:5. The common curve radius is 15.0<br />
m. A typical ramp runs in loops, with<br />
grade 1:7 on straight sections, reduced<br />
to 1:10 on curves.<br />
raising <strong>and</strong> winzing<br />
Raises are steeply inclined openings,<br />
connecting the mine’s sub levels at dif-<br />
ferent vertical elevations, used for lad-<br />
derways, orepasses, or ventilation. Inclination<br />
varies from 55 degrees, which<br />
is the lowest angle for gravity transport<br />
of blasted rock, to vertical, with crosssections<br />
from 0.5 to 30 sq m. When the<br />
excavation of raises is progressing down-<br />
wards they are called winzes.<br />
Manual excavation of raises is a<br />
tough <strong>and</strong> dangerous job, where the<br />
miner climbs the raise by extending the<br />
ladderway, installs the temporary platform,<br />
<strong>and</strong> drills <strong>and</strong> charges the round<br />
above his head. As such, manual raises<br />
are limited to 50 m-high. However, the<br />
efficiency can be greatly improved by<br />
using a raise climber up to 300 m.<br />
Firing sequence of a typical hole pattern (*contour holes).<br />
The drop raise technique is used for<br />
slot raises <strong>and</strong> short orepasses, using<br />
longhole drilling <strong>and</strong> retreat blasting<br />
from bottom to top, see figure below.<br />
Inverted drop raising is performed the<br />
other way around.<br />
raise boring<br />
The raise boring machine (RBM) may be<br />
used for boring ventilation raises, ore-<br />
passes, rock fill passes, <strong>and</strong> slot raises.<br />
Long hole drilling alternative to raise boring.<br />
Mine inFraSTruCTure<br />
It provides safer <strong>and</strong> more efficient me-<br />
chanized excavation of circular raises,<br />
up to 6 m-diameter.<br />
In conventional raise boring, a down-<br />
ward pilot hole is drilled to the target<br />
level, where the bit is removed <strong>and</strong> re-<br />
placed by a reaming head. The RBM<br />
then reams back the hole to final dia-<br />
meter, rotating <strong>and</strong> pulling the reaming<br />
head upward. The cuttings fall to the<br />
lower level, <strong>and</strong> are removed by any<br />
convenient method. An RBM can also<br />
underground mining methods 23<br />
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