Mining_Methods_UnderGround_Mining - Mining and Blasting

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