Mining_Methods_UnderGround_Mining - Mining and Blasting

4500N
Advance south
Stoping sequence at Mount Isa mine.
The new orebodies, 1,500-1,800 m
below the surface, are accessed by declines
from the bottom of the main U62/
R62 Mount Isa shaft complex. Central
to Enterprise is the new ore handling
system, including a 2 km underground
conveyor (V63 and M62) and a 713
m-deep, 5.3 m-diameter internal shaft
(the M62), which is boosting capacity
to extract the high-grade ore. A 2.13 m
x 1.98 m jaw crusher reduces the ore
down to less than 400 mm pieces at a
rate of up to 1,000 t/h. The 378 m-long
V63 conveyor carries the crushed ore to
the M62 shaft, where it is hoisted to the
20 level. The hoist is controlled from
a surface control room, and operates
at up to 16.8 m/s. From there the ore
is loaded onto the M62 conveyor for
delivery to the existing U62 copper
ore handling shaft via a short orepass.
Commercial production began from
Enterprise in July, 2000 following five
years of development work. The ore has
a high grade of 4% copper, justifying
development at such depths. The development
is predicted to provide ore for
the smelter after 2020, as production
from the 1100 orebody declines. Annual
production increased to 3.5 million t of
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5000N
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ore by 2004.The other main copper
resources at Mount Isa are the 1900 and
1100 orebodies, the latter known also as
the X41 mine named after the shaft that
reaches the 21 level.
MIM Holdings’ lead-zinc-silver comes
from the company’s lead mine at
Mount Isa (Racecourse orebody, etc)
and its George Fischer mine. At these
mines the lead-zinc-silver ore is mined,
crushed and hauled to the surface. Ore
from the George Fischer mine is taken
via an off-highway haulage road to the
Mount Isa facility for processing.
The total extent of the Mount Isa
mine workings is now 5 km in length
and 1.2 km in width, with the deepest
point (Enterprise mine) approximately
1,800 m underground.
Mining methods
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S48 Fault
Egg crater pattern
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Primary Stope
Secondary Stope
Tertiary Stope
The zinc-lead-silver orebodies and
copper orebodies are mined separately,
using slightly different methods, although
all operations use forms of open
stoping. In open stoping, blocks of ore
that make up part of the orebody are removed
one at a time, with the ultimate
goal of removing all of them.
MOunT iSa, auSTralia
Pre-existing primary stopes
In the Mount Isa copper mine orebodies,
sub-level open stoping, coupled
with secondary and tertiary stoping is
used to extract the ore. Blocks of ore
40 m-wide, 40 m-long at full orebody
height are removed. To do this, 5.0 m
x 5.0 m drilling sublevels are developed
at 40 m intervals. At the bottom of
the stope, a number of drawpoints are
mined and equipped to extract the ore.
Blast hole drilling is carried out using
a variety of Atlas Copco Simba rigs, in-
cluding models H4353, H1354, 366, 269
and 254. On the extraction level, upholes
in a ‘V’ shape are used to shape the
trough. On the drilling sublevel, the
Simba rigs are used to drill holes in a
radiating fan shape. A slice of ore the
height of the stope is extracted first,
exposing an open area along one side of
the stope, into which progressive bla-
sting is carried out.
The fleet of Simba rigs covers a wide
range of hole lengths, diameters and
orientation possibilities for flexible ore-
body exploitation capabilities. Holes can
be drilled accurately, with stringent tolerances,
for optimum fragmentation of
the ore, and minimal underbreak. Tophammer
or ITH (in-the-hole) hammer
underground mining methods 101
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5500N
1500E
2000E