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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Jedlovec<br />
JelSˇ aVa, SlOVakia<br />
Main Level<br />
Milková<br />
Idealised section of the mining operations <strong>and</strong> process plant at SMZ (Industrial Minerals).<br />
1. Ventilation (in) raises or airway raises 2. Ventilation (out) raises or exhaust airway<br />
diabase, comprises graphitic slate,<br />
bench-like dolomite, <strong>and</strong> the dolomite<br />
which hosts the magnesite. Graphitic<br />
slate also overlies the dolomite.<br />
Magnesite formation has been dated<br />
at 320 million years <strong>and</strong> the mechanism<br />
is thought to have been hydrothermal<br />
alteration of a fine-grained Carboniferous<br />
limestone bioherm. The orebody<br />
is estimated to be 4,000 m-long,<br />
Sequence of room <strong>and</strong> pillar mining.<br />
6<br />
3<br />
3. Ore passes (raises 4. Re-fill raises 5. Inner pillar 6. Re-fill<br />
1<br />
Dúbrava<br />
500 m a.s.<br />
323 m<br />
450 m a.s.<br />
1<br />
220 m a.s.<br />
400 m a.s.<br />
1,000 m-wide <strong>and</strong> 400 m-thick, but is<br />
irregular in shape <strong>and</strong> contains cavities<br />
often filled with ochre. However, it is<br />
structurally sound, to the extent that it<br />
could be mined with pillar support <strong>and</strong><br />
no rock reinforcement. The raw magnesite<br />
analyses 36-44% MgO, 48-50%<br />
CO 2 , 0.1-12% CaO, 0-2.3% SiO 2 <strong>and</strong><br />
3.2-6% Fe 2 O 3 . The specific mineralogy<br />
makes Jelšava magnesite a unique<br />
1. Fresh air ventilation raises 2. Exhaust airways 3. Ore passes<br />
4. Re-fill raises 5. Pillars 6. Re-fill<br />
4<br />
5<br />
source of ferric magnesium, this being<br />
one reason why it is imported by consumers<br />
so far away. SMZ estimates a<br />
reserve sufficient for 150 years’ mining<br />
at the present production rate of 1.2 million<br />
t/y.<br />
room <strong>and</strong> pillar<br />
Around 35% of the ore is mined by the<br />
room <strong>and</strong> pillar method in blocks which<br />
are up to 100 m-long, 50 m-high <strong>and</strong> 30<br />
m-wide, with 10 m-wide pillars along<br />
the short <strong>and</strong> long walls of the chamber,<br />
<strong>and</strong> a crown pillar at the top. Within<br />
these blocks, it is impossible to avoid<br />
mining some lower grade material, <strong>and</strong><br />
this is stored in surface dumps.<br />
Parallel uphole <strong>and</strong> inclined hole<br />
drilling up to 30 m was initially used<br />
for blasting the chambers, but the mine<br />
later switched to fan drilling in order<br />
to achieve better mining efficiency <strong>and</strong><br />
safety.<br />
This method again allows the mining<br />
of long, high blocks of magnesite up to<br />
200 m x 300 m x 60 m, mined in up to<br />
five ascending slices.<br />
The technique provides much greater<br />
stability in the rock mass because, not<br />
only are the rooms lower at 4.8 m to<br />
70 underground mining methods<br />
2<br />
2<br />
3<br />
1. Crushing 1st level<br />
2. Crushing 2nd level<br />
3. Suspension separator<br />
4. Rotary kiln, shaft kiln<br />
5. Electro-magnetic separation<br />
6. Forwarding department<br />
4<br />
4<br />
5 6<br />
5