Mining_Methods_UnderGround_Mining - Mining and Blasting

History
Mining has been conducted at Garpenberg
since the 13th century. The present
operations started in 1950-53, when
AB Zinkgruvor developed a new main
shaft and concrete headframe and the
adjacent concentrator. Boliden acquired
the mine in 1957 and completed the
development of a second shaft in 1972,
accessing the 800 m level at Garpenberg
North, having a hoisting capacity of
850,000 t/y and effectively creating a
second and larger mine.
Between these two shafts, the company
located another orebody under a
lake at Dammsjön and, in the 1980s,
considered draining the lake in order
to develop an open pit.
The mineralization in the Garpenberg
area occurs in a long, narrow synclinal
structure which is believed to be
Middle Precambrian, but may have been
remobilized later. The orebodies are
vertically extensive lenses that are usually
narrow, much folded and therefore
twisting and irregular.
Cut and fill
Until very recently all of the ore, subdivided
in 100 m-high slices, was extracted
by cut-and-fill mining, taking
garPenBerg, Sweden
innovative mining at garpenberg
0 Z
400 Z
800 Z
1200 Z
Garpenberg
Lina shaft
Kanal Ore
Strand Ore
Potential ?
One million
tonnes of ore
Gruvsjö shaft
Capacity: 450 000 tpa Smältarmossen
Finnhyttan
Tyskgården
Production levels
Potential areas outside ore reserves 2005-01
The Garpenberg mine, located
200 km northwest of Stockholm,
extracts more than 1 million t/y of
ore. The ore is polymetallic and
contains mainly zinc, silver and
also some lead, copper and gold.
Additionally, about 500,000 t of
development waste is excavated
annually. Over recent years, Gar-
penberg has been forced to add
reserves, or reconsider its future.
Happily, more orebodies have
been discovered, and new stoping
methods and drilling technology
introduced. Atlas Copco has co-
operated closely with Garpenberg
management to resolve technical
issues, designing and supplying
equipment to suit the
evolving objectives. As a result,
the mine achieved over 1 Mt of
ore in 2005, at very acceptable
grades.
?
?
Dammsjön
Dammsjö Agmin
500-785 Z
925-1100 Z
700-
1000 Z
Dammsjön Kvarnberget
Lappberget
Kaspersbo
910 Z
1000-1300 Z
5-6 m-thick slices drilled horizontally
from 50-300 m-long and up to 15 mwide
stopes. Rock fill was used in the
bottom cut, and either plain sand or
cemented hydraulic fill above. The
sand comes from the coarse fraction of
the mill tailings, and the fill is supplemented
by development waste.
Mining starts normally at the centre
of the base level of the stope and progresses
towards the ends and upwards.
The last cut, just below the crown pillar,
is heavily reinforced to facilitate the
recovery of the 8-15 m-high pillar using
up holes drilling and blasting.
The undercut-and-fill method, progressing
downwards, was used in the
Strandgruvan section from the mid-70s
until 2001, when the ore was mined out.
This method provided a safe working
roof in the weak, fractured ore with
unstable footwall, for just the extra
cost of cement and rebar reinforcement.
The method was suited to the orebody
irregularities, and no crown pillar had
to be left or recovered. The introduction
of trackless mining and further exploration
of the mineralization in the North
underground mining methods 47
500-
800 Z
1100-
1400 Z
Garpenberg North
Shaft
Capacity: 850 000 tpa
Gransjön
1600 Y 2000 Y 2400 Y 2800 Y 3200 Y 3600 Y 4000 Y 4400 Y 4800 Y 5200 Y
Idealized long section at Garpenberg showing all orebodies and shafts.
870 Z
0 Z
400 Z
800 Z
1200 Z