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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<strong>Mining</strong> in flat orebodies<br />
nearly horizontal<br />
extraction<br />
Variations on room-<strong>and</strong>-pillar <strong>and</strong><br />
longwall mining techniques have<br />
always been attractive propositions<br />
for mechanization, because<br />
of the near horizontality of such<br />
systems. Until recently, trackless<br />
equipment was limited to a minimum<br />
working headroom of 2 m<br />
or more. However, major developments<br />
in Polish copper mines<br />
<strong>and</strong> in gold <strong>and</strong> platinum mines<br />
in South Africa have spawned a<br />
new generation of thin-seam <strong>and</strong><br />
narrow mining equipment from<br />
Atlas Copco that can work in substantially<br />
less space than previously<br />
thought possible. The Rocket<br />
Boomer S1 L, for instance, has a<br />
tramming height of just 1.3 m, yet<br />
can cover a face area of up to 29<br />
sq m. Likewise, the Scooptram<br />
ST 600LP loader equipped with<br />
video cameras to assist the driver<br />
has a height of only 1.56 m, but still<br />
carries a 6 t payload. Availability<br />
of such machines is already revolutionizing<br />
the design approach<br />
to mining flat orebodies.<br />
room <strong>and</strong> pillar<br />
Room <strong>and</strong> pillar is designed for mining<br />
of flat, bedded deposits of limited thick-<br />
ness. Examples are sedimentary deposits,<br />
like copper shale, limestone or<br />
s<strong>and</strong>stone containing lead, coal seams,<br />
salt <strong>and</strong> potash layers, limestone <strong>and</strong><br />
dolomite.<br />
The method recovers the mineraliza-<br />
tion in open stopes, leaving pillars of<br />
ore to support the roof. To recover the<br />
maximum amount of ore, miners aim to<br />
leave smallest possible pillars behind,<br />
because these are difficult <strong>and</strong> expen-<br />
sive to recover. The roof must remain<br />
intact, <strong>and</strong> rockbolts are used extensively<br />
as rock reinforcement. Rooms<br />
<strong>and</strong> pillars are normally arranged in<br />
regular patterns, <strong>and</strong> can be designed<br />
with circular pillars, square pillars, or<br />
elongated walls separating the rooms.<br />
Classic room <strong>and</strong> pillar applies to<br />
flat, bedded deposits with moderate to<br />
Vertical benching<br />
Benching of thicker parts<br />
Classic room <strong>and</strong> pillar layout.<br />
large thickness, also to inclined deposits<br />
with larger thickness. <strong>Mining</strong> the<br />
orebody creates large openings, where<br />
trackless machines can travel on the<br />
flat floor. Orebodies with large vertical<br />
height are mined in horizontal slices,<br />
starting at the top <strong>and</strong> benching down<br />
in steps.<br />
Post room <strong>and</strong> pillar applies to inclined<br />
orebodies, of dip angle from 20<br />
to 55 degrees, with large vertical height,<br />
where mined out space is backfilled.<br />
The fill keeps the rock mass stable,<br />
<strong>and</strong> serves as the work platform while<br />
mining the next ore slice.<br />
Step room <strong>and</strong> pillar is an adaptation<br />
of trackless mining to orebodies with<br />
too steep a dip for rubber-tyred vehicles<br />
to operate in a regular room <strong>and</strong><br />
pillar layout. Haulage drifts <strong>and</strong> stopes<br />
are therefore angled diagonally across<br />
the dip, to create work areas with level<br />
floors off which trackless equipment<br />
can work. <strong>Mining</strong> advances downward,<br />
along the step room angle.<br />
Classic room <strong>and</strong> pillar<br />
Very little development work is required<br />
to prepare flat-bedded deposits for room<br />
<strong>and</strong> pillar mining, because access for<br />
ore transport <strong>and</strong> communication is<br />
through the production rooms.<br />
FlaT <strong>Mining</strong><br />
Ore production in flat room <strong>and</strong> pillar<br />
uses the same drill/blast techniques<br />
as in normal drifting. Where geological<br />
conditions are favourable, large-capacity<br />
drilling rigs <strong>and</strong> loaders can be used.<br />
High orebodies are mined in slices,<br />
starting at the top, rockbolting the roof<br />
from each bench. St<strong>and</strong>ard crawler rigs<br />
are used for drilling vertical holes <strong>and</strong><br />
conventional bench blasting. Horizontal<br />
drilling <strong>and</strong> flat benching is a more prac-<br />
tical alternative, using the same drilling<br />
equipment.<br />
The blasted ore is loaded using<br />
diesel or cable-electric LHD machines,<br />
<strong>and</strong>, where height permits, dump trucks<br />
may be used between stope <strong>and</strong> dump.<br />
In thin orebodies, loading points may<br />
be necessary for transferring ore from<br />
loader to hauler. As all activities are car-<br />
ried out on one or very few levels covering<br />
a large area, there are many faces available<br />
at any time, so high equipment utili-<br />
zation is possible.<br />
Post pillar<br />
© Atlas Copco Rock Drills AB, 2000<br />
Post pillar mining is a crossbreed of room<br />
<strong>and</strong> pillar <strong>and</strong> cut <strong>and</strong> fill mining. Post<br />
pillar mining recovers the mineralization<br />
in horizontal slices, starting from a<br />
bottom slice, advancing upwards. Pillars<br />
are left inside the stope to support the<br />
underground mining methods 39<br />
Pillar<br />
Pillar