Mining_Methods_UnderGround_Mining - Mining and Blasting
Mining_Methods_UnderGround_Mining - Mining and Blasting
Mining_Methods_UnderGround_Mining - Mining and Blasting
You also want an ePaper? Increase the reach of your titles
YUMPU automatically turns print PDFs into web optimized ePapers that Google loves.
Pillar<br />
between<br />
stopes<br />
5.0 m-high, but also the voids are filled,<br />
providing a bench for drilling the next<br />
slice as mining proceeds up each block.<br />
Pillars are 5 m x 5 m at 12 m spacing.<br />
The smaller rooms allow more selective<br />
mining, producing a higher proportion<br />
of processable magnesite, while the 4.4<br />
million t of waste material dumped on<br />
surface during chamber mining can<br />
now be used as fill. The fill rate is up<br />
to 300,000 t/y.<br />
In 1971, a new rail haulage was installed,<br />
equipped with locomotives <strong>and</strong><br />
20 t-capacity bottom-dump wagons.<br />
The rail system still h<strong>and</strong>les ore from<br />
the core area of the mine, but it is more<br />
cost effective to use truck haulage from<br />
more peripheral parts.<br />
Overh<strong>and</strong> stoping<br />
Open stope<br />
Overh<strong>and</strong> stoping room <strong>and</strong> pillar system at SMZ.<br />
Chamber <strong>and</strong> pillar mining has created<br />
a huge void within the mine, now totalling<br />
13 million cu m, <strong>and</strong> undercut sections<br />
of the hanging wall have collapsed<br />
in places.<br />
Studies resulted in an overh<strong>and</strong> stoping<br />
method being introduced in some<br />
of the mining blocks above the 323 m<br />
level from 1990 onwards, <strong>and</strong> this now<br />
accounts for 65% of production.<br />
By 1998, SMZ was looking to increase<br />
production <strong>and</strong> productivity in the overh<strong>and</strong><br />
stoping blocks. In consultation with<br />
Atlas Copco, the mine trialled a Rocket<br />
Boomer 282 equipped with a COP 1432<br />
Pillar with loading crosscut<br />
<strong>and</strong> transport drifts<br />
rock drill. This rig achieved the expected<br />
performance improvement, <strong>and</strong> was<br />
bought by SMZ, together with a Rocket<br />
Boomer 281 <strong>and</strong> a Simba H357, for precise<br />
<strong>and</strong> rapid pillar recovery. The latter<br />
unit was equipped with a COP 1838 rock<br />
drill. Switching from pneumatic to hydraulic<br />
drilling using the two Rocket<br />
Boomers increased overh<strong>and</strong> stoping<br />
magnesite output by a factor of four.<br />
In the overh<strong>and</strong> stoped sections muck<br />
is loaded by a fleet of three LHDs <strong>and</strong><br />
two wheel loaders. The LHDs typically<br />
JelSˇ aVa, SlOVakia<br />
tram to the ore passes that supply the<br />
rail haulage system, while the wheel<br />
loaders dump into trucks that may go<br />
either to the ore passes or directly to the<br />
primary crusher.<br />
new level development<br />
In 2000-2001 SMZ started to develop a<br />
new mining level at 220 m asl. Whereas<br />
extraction had thus far all been above<br />
the local erosion base level, providing<br />
natural drainage at 287 m asl, this new<br />
level is below the water table. The amount<br />
of water to be pumped out is equal<br />
to the amount of ore to be extracted.<br />
For initially driving the access ramp,<br />
<strong>and</strong> later development, plus some production<br />
drilling, Atlas Copco offered<br />
SMZ a new Rocket Boomer M2 C twinboom<br />
rig, <strong>and</strong> helped train six Simba<br />
operators to use it.<br />
Work on the ramp <strong>and</strong> some lateral<br />
development started in 2001 <strong>and</strong> was<br />
scheduled to take 3-4 years. The Rocket<br />
Boomer M2 C normally works either<br />
one or two of the mine’s three eighthour<br />
shifts on the ramp, but also works<br />
on production. The new level will be<br />
worked in 10 m-high slices, improving<br />
geotechnical conditions <strong>and</strong> saving on<br />
primary development costs. However,<br />
although many blocks of high quality<br />
magnesite are directly accessible using<br />
overh<strong>and</strong> stoping from the new level,<br />
underground mining methods 71<br />
Front<br />
pillar<br />
boundary<br />
pillar<br />
Rocket Boomer 281 drilling a crosscut entry.