Mining_Methods_UnderGround_Mining - Mining and Blasting

JelSˇ aVa, SlOVakia
Mining magnesite at Jelšava
Mechanization of
overhand stoping in
thick deposits
As Slovakia moved from centralized
control in the early 1990s, the
management of Jelsava magnesite
mine faced the accumulated
problems of over-exploitation and
under-mechanization. In the intervening
years, the mining method
has been revised, the equipment
inventory renewed, and the output
quality improved. Despite the
sometimes difficult economic situation,
accompanied by political
upheavals, the employee-owned
company SMZ that controls the
mining operation is doing well.
Atlas Copco and its local distributor
ISOP have been there to lend a
helping hand, as a result of which
Rocket Boomer drill rigs and Simba
longhole drill rigs have become
Jelšava’s main production tools.
Producing clinker
The fully mechanized underground mine
at Jelsava, operated by SMZ, feeds high
grade magnesite to on-site conversion
facilities with a capacity of 370,000 t/y
raw clinker. The process includes primary
and secondary crushing, followed
by dense medium separation to produce
a concentrate for thermal treatment in
shaft and rotary kilns. Electromagnetic
separators differentiate magnetic brickmaking
clinker from non-magnetic
steelmaking clinker.
SMZ’s raw Jelšava clinker is converted
to materials for metallurgical,
ceramic and agricultural use. Annual
production is around 352,000 t, comprising
167,000 t steelmaking clinker,
160,000 t of brickmaking clinker, and
25,000 t of basic monolithic refractory
mixes. Overall, 85% of SMZ output is
exported to 28 different countries.
To contain production costs SMZ has
been investing in more cost effective
mining, and plans to replace the rotary
kilns with more efficient twin-shaft
kilns that emit very little dust.
Map of Slovakia showing Jelsˇava location (Industrial Minerals).
geology
The Dúbrava-Miková orebody that SMZ
exploits is the largest of 12 significant
magnesite deposits in Slovakia. These
extend from Podrecany in the west to
Bankov, near Košice, in the east and were
all mined for varying periods during the
20 th Century. The mineralization is part
of a magnesite belt extending from cen-
tral Austria to the Slovakia-Ukraine border.
Within Slovakia, the deposits occur
mainly in the Slovenské Rudohorie
mountains, and Jelšava is in the deeply
dissected Revűcka highland area of this
Rocket Boomer M2 C moving towards the faces.
range. The magnesite deposit extends
over 325 hectares within a spur of the
Magura hill mass, and the maximum
altitude of this spur is 675 m asl. The
underground mine is accessed laterally
from portals in the sides of the spur,
and mineral moves through the process
plant downhill from the primary
crusher, which is outside the mine on
the same level as the main haulage.
The magnesite is part of a sedimentary
sequence that has been subjected
to tectonic forces and metamorphism,
especially during the Variscan and Al-
pine events. This sequence, underlain by
underground mining methods 69