Mining Methods
in Underground Mining
Atlas Copco
Mining Methods
in Underground Mining
www.atlascopco.com
2008
Contents
Foreword
2 Foreword by Lars Bergkvist,
Talking Technically
3 Trends in underground mining
7 Geology for underground mining
13 Mineral prospecting and exploration
17 Finding the right balance in exploration drilling
21 Underground mining infrastructure
25 Rapid development in mining
28 Principles of raiseboring
31 Mechanized bolting and screening
35 Mining in steep orebodies
40 Mining in flat orebodies
43 Backfilling for safety and profit
46 Atlas Copco rock bolts for mining
Case Studies
47 Improving output at Garpenberg
53 Changing systems at Zinkgruvan
59 Increasing outputs at LKAB iron ore mines
63 Production control at Kemi chrome mine
69 Mining magnesite at Jelava
Front cover:
Headframe at Australia's
Golden Grove mine.
Produced by Atlas Copco Rock Drills AB, SE-701 91 rebro, Sweden, tel +46 19 670 70 00, fax 019-670 73 93. Publisher: Ulf Linder, ulf.linder@se.atlascopco.com
Production Manager: Patrik Johansson, patrik.johansson@se.atlascopco.com Editor: Mike Smith, mike@tunnelbuilder.com
Senior Adviser: Lars Bergkvist, lars.bergkvist@se.atlascopco.com
Contributors: Marcus Eklind, Patrik Ericsson, Hans Fernberg, Jan Jnsson, Mathias Lewn, Gunnar Nord, Bjrn Samuelsson,
all name.surname@se.atlascopco.com, Adriana Potts adriana.potts@ntlworld.com, Kyran Casteel kyrancasteel@aol.com, Magnus Ericsson
magnus.ericsson@rmg.se. The editor gratefully acknowledges extracts from Underground Mining Methods engineering fundamentals
and international case studies by William A Hustrulid and Richard L Bullock, published by SME, details from www.smenet.org
Digital copies of all Atlas Copco reference editions can be ordered from the publisher, address above, or online at www.atlascopco.com/rock.
Reproduction of individual articles only by agreement with the publisher.
Edited by Mike Smith, tunnelbuilder ltd, United Kingdom. Designed and typeset by ahrt, rebro, Sweden. Printed by Prinfo Welins Tryckeri, Sweden.
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Copyright 2008, Atlas Copco Rock Drills AB, rebro, Sweden. All product names in this publication are trademarks of Atlas Copco.
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Foreword
Welcome to the underground world of mining
Since ancient times, development of underground mining
techniques has been driven by the needs of man, starting
with simple and primitive methods and advancing to todays
highly productive systems by which ore is mined from great
depths in enormous quantities.
So, what about the mining methods? Many have been tested
throughout the years, with some producing better results than
others, and accidents have happened when things have gone
wrong. However, a variety of safe methods have resulted
which are now applied around the world.
Lars Bergkvist
Senior Adviser Mining
Atlas Copco Rock Drills AB
lars.bergkvist@se.atlascopco.com
Mining trends
Stable growth
Investments into new mines have increased dramatically and all indicators
point to a continued high level of project activities during the next couple of
years, see figure 1.
Whatever the investment activities
or metal prices, the amount of metal
produced every year in global mining
is fairly stable and increasing slowly but
steadily. Total volumes of rock and ore
handled in the global mining industry
amount to approximately 30,000 Mt/y.
This figure includes ore and barren rock
and covers metals, industrial minerals
and coal. Roughly 50% are metals, coal
about 45%, and industrial minerals
account for the remainder.
M USD
30 000
25 000
n
Tre
20 000
15 000
ds
Trends
10 000
5 000
2001
2002
2003
2004
2005
2006
9/18/07
9:05:34 PM
Mining trends
gold
copper
iron ore
nickel
lead
zinc
PGMs
diamonds
other
Metal ore
Global metal ore production is around
5,000 Mt/y. Open pit mining accounts
for some 83% of this, with underground
methods producing the remaining 17%.
Barren rock production from underground operations is small, not exceeding 10% of total ore production, but the
barren rock production from open pit
operations is significant.
Open pits typically have a strip ratio,
the amount of overburden that has to be
removed for every tonne of ore, of 2.5.
Based on this assumption, the amount
of barren rock produced can be calculated as some 10,000 Mt/y. In total, the
amount of rock moved in the metals mining business globally is hence around
15,000 Mt/y. The dominance of open pit
operations stems in terms of the amounts
of rock handled, to a large extent, from
the necessary removal of overburden,
which is often drilled and blasted.
By necessity, the open pit operations
are larger than the underground ones.
The map below shows the distribution
of metal ore production around the
world, and also the split between open
pit and underground tonnages.
Metal ore production from open pits (green), underground (red). (Raw Materials Data 2005)
Total 5 000 Mt
Europe + Russia
401/188 Mt
898/77 Mt
750/185 Mt
244/175 Mt
1319/117 Mt
455/85 Mt
open pit
underground
Future
Development of new mining technologies is driven by a range of underlying
factors, which affect all stakeholders.
Mines are getting deeper and hotter, and
are now more often located in harsh environments.
Legislation, particularly concerning
emissions, and increased demands on
Mining methods in underground mining
Mining trends
Waste
(Mt)
Total
(Mt)
Metals
850
85
935
Open pit
Underground
4 130
10 325
14 500
47
Total
4 980
10 410
15 400
50
Industrial minerals
Underground
65
70
Open pit
535
965
1 500
Total
600
970
1 570
5 600
11 400
17 000
55
Sub total
Coal
Underground
2 950
575
3 500
12
Open pit
2 900
7 250
10 000
33
Total
5 850
7 825
13 500
45
Overall total
11 450
19 225
30 700
100
Assumptions: 10% waste in underground metal and industrial mineral operations. Strip ratio (overburden/ore) in open
pit metal operations is 2.5. The strip ratio in industrial minerals is 1.8. For coal, underground barren rock is set at 20%, and the strip
ratio in open-pit mines is 2.5. Industrial minerals includes limestone, kaolin, etc. but excludes crushed rock and other construction
materials. Salt, dimensional stones, precious stones are not included. Diamonds are included in metals.
Magnus Ericsson
2500
2
1.8
2000
1000
1.6
1.4
1.2
1
0.8
500
0.6
0.4
0.2
0
1500
1930
1945
1960
Copper production
1975
1988
1991
Ore production
1994
1997
Copper/ore metal
production (mt)
2000
Mining trends
Bingham Canyon copper mine near Salt Lake City, Utah, USA.
8. Metamorphic sandstone
high proportion of quartz.
9. Metamorphic limestone as
marble, etc calcite and dolomite.
10. Metamorphic shales as
slates, schists, etc. with
garnet, mica, feldspar.
11. Contact zones between
igneous and country rocks
garnet, hornblende, sulphides.
Minerals
In some circumstances, the properties
of individual minerals can be important to the means of mining, and will
certainly be important for the means
of extraction of the materials to be exploited. More often, however, minerals
will be mixed with others to form the
various types of rocks, and the properties will be combined to form both
homogenous and heterogeneous structures. Feldspar accounts for almost
50% of the mineral composition of
the earths crust. Next come the pyroxene and amphibole minerals, closely
followed by quartz and mica. These
minerals all make up about 90% of the
composition of the earths crust.
Minerals have a wide variety of properties that can be important in their
usefulness to man, and to the best way
7
Amphibolite.
Properties
Rocks, normally comprising a mixture
of minerals, not only combine the properties of these minerals, but also exhibit
properties resulting from the way in
which the rocks have been formed, or
perhaps subsequently altered by heat,
pressure and other forces in the earths
Mohs hardness
scale
1
Typical mineral
Identification of hardness
Talc
Gypsum
Calcite
Fluorite
Apatite
10
Dolomitic limestone.
Sandstone.
Gneiss.
Many salts, for example, are particularly elastic, and can absorb the shocks
of blasting without a second free face
being cut, thereby directly influencing
mining method.
The drillability of a rock depends
on, among other things, the hardness
of its constituent minerals, and on the
grain size and crystal form, if any.
Quartz is one of the commonest minerals in rocks. Since quartz is a very
hard material, high quartz content in
rock can make it very hard to drill, and
will certainly cause heavy wear, particularly on drill bits. This is known as
abrasion. Conversely, a rock with a high
content of calcite can be comparatively
easy to drill, and cause little wear
on drill bits. As regards crystal form,
minerals with high symmetry, such as
cubic galena, are easier to drill than
minerals with low symmetry, such as
amphiboles and pyroxenes.
A coarse-grained structure is easier
to drill, and causes less wear of the drill
string than a fine-grained structure. Consequently, rocks with essentially the
same mineral content may be very different in terms of drillability. For example, quartzite can be fine-grained
Igneous rocks
Igneous rocks are formed when magma solidifies, whether plutonic rock,
deep in the earths crust as it rises to
the surface in dykes cutting across other
rock or sills following bedding planes,
or volcanic, as lava or ash on the surface. The most important mineral constituents are quartz and silicates of various types, but mainly feldspars. Plutonic
rocks solidify slowly, and are therefore
coarse-grained, whilst volcanic rocks
solidify comparatively quickly and
Sedimentary rocks
Sedimentary rocks are formed by the
deposition of material, by mechanical or
chemical action, and its consolidation
under the pressure of overburden. This
generally increases the hardness of the
rock with age, depending on its mineral
composition. Most commonly, sedimentary rocks are formed by mechanical
action such as weathering or abrasion
on a rock mass, its transportation by a
medium such as flowing water or air,
and subsequent deposition, usually in
still water. Thus, the original rock will
partially determine the characteristics
of the sedimentary rock. Weathering or
erosion may proceed at different rates,
as will the transportation, affected by
the climate at the time and the nature
of the original rock. These will also
affect the nature of the rock eventually
formed, as will the conditions of deposition. Special cases of sedimentary rock
include those formed by chemical deposition, such as salts and limestones, and
organic material such as coral and shell
Plutonic rocks
Dykes and Sills
Silica (SiO2)
content
Volcanic (mainly
lava)
Basic <52%
SiO2
Gabbro
Diabase
Basalt
Intermediate
52-65%
SiO2
Diorite
Porphyrite
Andesite
Syenite
Syenite
Trachyte porphyry
Acidic >65%
Quartz diorite
SiO2
Granodiorite
Granite
Rhyodacite
Rhyolite
Mineral deposit
exploration
There will be a delicate economic balance between an investment in development drives in stable ground, perhaps
without useful mineralization, and
Original material
Sandstone
Sand
Metamorphic rocks
The effects of chemical action, increased
pressure due to ground movement, and/
or temperature of a rock formation can
sometimes be sufficiently great to cause
a transformation in the internal structure and/or mineral composition of
the original rock. This is called metamorphism. For example, pressure and
temperature may increase under the
influence of up-welling magma, or because the strata have sunk deeper into
the earths crust. This will result in
the recrystallization of the minerals,
or the formation of new minerals. A
characteristic of metamorphic rocks is
that they are formed without complete
remelting, or else they would be termed
igneous. The metamorphic action often
makes the rocks harder and denser, and
more difficult to drill. However, many
metamorphic zones, particularly formed
in the contact zones adjacent to igneous
10
Original rock
Degree of metamorphism
Amphibolite
High
Mica schist
Medium to high
Gneiss
High
Green-schist
Low
Quartzite
Sandstone
Medium to high
Leptite
Dacite
Medium
Slate
Shale
Low
Veined gneiss
High
Marble
Limestone
Low
drives within the mineral deposit, perhaps of shorter life, but requiring more
support measures. Setting aside support requirements, in general terms it
would seem beneficial to carry out as
much of the development work as possible within the mineral deposit, making development drives in non-productive gangue rocks as short as possible. However, it may be decided that a
major development asset, such as a shaft
or transport level, should be in as stable
a ground area that can be found, with
further drives or levels made from it.
In extreme cases, it may be found
that the mineral deposit cannot support
development workings without considerable expense. In these circumstances,
it might be better to make development
drives near and below the mineral deposit, and exploit it with little direct entry, such as by longhole drilling and
blasting, with the ore being drawn off
from below.
Depending on the amount of disturbance that the mineral-bearing strata
has been subjected to, the mineral deposit can vary in shape from stratified
rock at various inclinations, to highly
contorted and irregular vein formations
requiring a very irregular development
pattern.
The latter may require small drives
to exploit valuable minerals, although
the productivity of modern mining
equipment makes larger section drives
more economic, despite the excavation
of more waste rock.
The tendency of a rock to fracture,
sometimes unpredictably, is also important to determine drivage factors,
such as support requirements, and the
charging of peripheral holes to prevent
overbreak. Although overbreak may not
be so important in mining as in civil
tunnelling, it can still be a safety consideration to prevent the excavation of
too much gangue material, and to preserve the structure of a drive.
Investigation and
exploration
It is clear that rock structures, and the
minerals they contain, can result in a
wide variety of possible mining strategies. Obviously, the more information
that is gained, the better should be the
Diabase.
Granite.
11
Marble
Limestone
Bjrn Samuelsson
Prospecting
Prospecting involves searching a district
for minerals with a view to further operation. Exploration, while it sounds similar to prospecting, is the term used
for systematic examination of a deposit.
It is not easy to define the point where
prospecting turns into exploration.
A geologist prospecting a district is
looking for surface exposure of minerals, by observing irregularities in colour, shape or rock composition. He uses
a hammer, a magnifying glass and some
other simple instruments to examine
whatever seems to be of interest. His
experience tells him where to look, to
have the greatest chances of success.
Sometimes he will stumble across ancient, shallow mine workings, which
may be what led him to prospect that
particular area in the first place.
Soil-covered ground is inaccessible
to the prospector, whose first check
would be to look for an outcrop of the
mineralization. Where the ground cover
comprises a shallow layer of alluviums,
trenches can be dug across the mineralized area to expose the bedrock. A
prospector will identify the discovery,
measure both width and length, and
calculate the mineralized area. Rock
samples from trenches are sent to the
laboratory for analysis. Even when minerals show on surface, determining any
extension in depth is a matter of qualified guesswork. If the prospector's
findings, and his theorizing about the
probable existence of an orebody are
solid, the next step would be to explore
Geophysical exploration
From surface, different geophysical methods are used to explore subsurface formations, based on the physical properties of rock and metal bearing minerals
such as magnetism, gravity, electrical
13
Surveys
Magnetic surveys measure variations
in the Earth's magnetic field caused by
magnetic properties of subsurface rock
formations. In prospecting for metallic
minerals, these techniques are particularly useful for locating magnetite,
pyrrhotite and ilmenite. Electromagnetic
surveys are based on variations of electric conductivity in the rock mass. An
electric conductor is used to create a
primary alternating electromagnetic
field. Induced currents produce a secondary field in the rock mass. The resultant field can be traced and measured, thus revealing the conductivity
14
specialities, the main one being to detect the presence of metals in the topsoil cover. By taking a large number of
samples over an extended area and
analyzing the minute contents of each
metal, regions of interest are identified. The area is then selected for more
detailed studies.
Exploratory drilling
For a driller, all other exploration methods are like beating about the bush.
Drilling penetrates deep into the ground,
and brings up samples of whatever it
finds on its way. If there is any mineralization at given points far beneath the
surface, drilling can give a straightforward answer, and can quantify its
presence at that particular point.
There are two main methods of exploratory drilling. The most common,
core drilling, yields a solid cylinder
shaped sample of the ground at an
exact depth. Percussion drilling yields
a crushed sample, comprising cuttings
from a fairly well-determined depth
Core drilling
In 1863, the Swiss engineer M Lescot
designed a tube with a diamond set face,
for drilling in the Mount Cenis tunnel,
where the rock was too hard for conven-tional tools. The intention was to
explore rock quality ahead of the tunnel
face, and warn miners of possible rock
falls.
Exploration Results
Mineral Resources
Ore Reserves
Inferred
Increasing level
of geological
knowledge and
confidence
Indicated
Probable
Measured
Proved
The 2004 Australasian code for reporting exploration results, mineral resources and ore reserves.
Reverse circulation
drilling
To obtain information from large orebodies where minerals are not concentrated in narrow veins, reverse circulation
16
drilling is used. Reverse circulation drilling is a fast, but inaccurate, exploration method, which uses near-standard
percussion drilling equipment. The
f lushing media is introduced at the
hole collar in the annular space of a
double-tubed drill string, and pushed
down to the bottom of the hole to flush
the cuttings up through the inner tube.
The drill cuttings discharged on surface are sampled to identify variations
in the mineralization of the rock mass.
Reverse circulation drilling uses much
heavier equipment than core drilling,
and has thus a limited scope in depth.
From prospecting to
mining
Every orebody has its own story, but
there is often a sequence of findings.
After a certain area catches the interest
of the geologists, because of ancient
mine works, mineral outcrops or geological similarities, a decision is taken
to prospect the area. If prospecting confirms the initial interest, some geophysical work might be carried out. If interest still persists, the next step would be
to core drill a few holes to find out if
there is any mineralization.
To quantify the mineralization, and
to define the shape and size of the ore
body, then entails large investment to
drill exploratory holes in the required
patterns.
Hans Fernberg
Right Balance
There are pros and cons with both RC drilling and core drilling.
Fast and
economical
RC drilling
without taking
samples
Pre-collaring
17
Right Balance
Scenario 1
100% core drilling
457 days
Scenario 2
50% RC (pre-collars only), 50% core drilling
301 days
Scenario 3
75% RC (pre-collars & full holes), 25% core drilling
223 days
In case three core drilling rigs would have been available in scenario 1, expected time is
152 days compared with 457 days.
In case three core drilling rigs would have been available in scenario 2, expected time is
149 days compared with 301 days.
A rough conclusion gives that the RC rig is somewhat faster than 3 core drilling rigs together.
457 days
301 day
223 day
2,580,000 USD
740,000 USD
320,000 USD
Table 2.
Table 1.
Cost factor
Time factor
18
of parts, fuel, casing, water, and consumables also have a direct influence
on the number of metres drilled per
shift.
Significant time savings can be achieved by using RC and core drilling in
a balanced combination (see table 1).
Here we can see that one RC rig can be
used to drill enough pre-collars to keep
three core drilling rigs running for 24
h/day. The time factors show obvious
benefits using a combination of the two
methods. In this scenario, a minimum
of 25% of the total metres drilled were
specified as core drilling.
Confidence factor
The third variable in the equation is
the confidence factor, because investors
and geologists place strict demands on
contractors to deliver the highest quality geological information. Investors
always require a fast return on their investments, and the geologists need solid
results for the mine planners. However,
whenever a gold nugget is found, the
Mining methods in underground mining
Right Balance
100
%
rC drilling
Core drilling
80
60
40
20
0
Canada
Latin
America
russia
China
Australia
SE Asia
uSA
Africa
Ratios between core and RC drilling. The figures reflect total exploration expenditures from national statistics for surface and underground.
Jan Jnsson
Increased usage of
RC drilling
RC drilling is on the increase, and may
well account for 55% of all metres
drilled in 2008. The diagram above
shows some estimated ratios between
core and RC drilling in different parts
of the world in 2002. In terms of metres
drilled, RC accounts for 50% and core
drilling for 50%. Tradition and environmental impact play large roles. RC rigs
are heavy, and are mounted on trucks
or track carriers. This fact tends to
19
Right Balance
Explorac 220RC.
20
Mine Infrastructure
Underground infrastructure
Mining methods used underground are
adapted to the rock conditions, and the
shape, dimensions, strength and stability of the orebody. In order to work the
underground rock mass, infrastructure
is required for access to work places, ore
production, power supply, transport of
ore, ventilation, drainage and pumping
as well as maintenance of equipment.
Traditionally, the most common method to transport men, material, ore and
waste is via vertical shafts. The shaft
forms the access to the various main underground levels, and is the mines main
artery for anything going up or down.
Shaft stations, drifts and ramps connect
Services
Electric power is distributed throughout
the mine, and is used to illuminate work
21
Mine Infrastructure
Transport infrastructure
Headframe
Production
plant
Settling
pond
Tailings
Skip
Ventilation
shaft
Open pit
(mined out)
Decline
Abandoned
Mined out
and
backfilled
level
Ore
pass
Sublevel
Cage
Main level
Producing
stopes
Crusher
Haulage level
Development
of stopes
Internal
ramp
Workshop,
fuelling,
storage
Ore
bin
Ore
Measuring
pocket
Exploration
Skip
Water basin
Pump station
Conveyor belt
Skip filling
station
Sump
Drilling
Future reserves?
Mine Infrastructure
Raiseboring
The raiseboring machine (RBM) may be
used for boring ventilation raises, orepasses, rock fill passes, and slot raises.
4
3
3
1
1
3
4
3
4
23
Mine Infrastructure
space for consecutive blasting. The drilling and blasting results are shown below.
Hole opening, or downreaming, using
a small-diameter reamer to enlarge an
existing pilot hole, can also be carried
out by an RBM.
The capital cost of an RBM is high,
but, if used methodically and consistently, the return on investment is very
worthwhile. Not only will raises be
constructed safer and faster, they will
be longer, smoother, less disruptive than
blasting, and yield less overbreak. The
rock chips produced by an RBM are consistent in size and easy to load.
The BorPak is a small, track-mounted
machine for upward boring of inclined
raises. It starts boring upwards through
a launching tube. Once into rock, grippers hold the body, while the head rotates and bores the rock fullface. BorPak
can bore blind raises with diameters from
1.2 m to 1.5 m, up to 300 m-long.
Gunnar Nord
Holes at breakthrough after 32 m.
24
Talking Technically
In perspective
Advance rates in tunnelling, despite substantial improvements in rock drilling
technology, have not increased radically
in recent years. Since the 1970s, the rate
at which tunnels have been built has
only increased by around 1% annually.
The improvements from 1973 to 2007
are described in Figure 1 with the
typical time needed for the different
operations at the tunnel face for a 70 m2
road tunnel. The bars represent the time
needed for the operations and metres
advance of the tunnel.
One reason for this is safety, the po
sitive effect of which can clearly be seen
in Figure 2. An example is charging of
blast holes concurrent with drilling is no
longer permitted, except in a few countries. Implementation of stricter rules
on safety and the working environment
has had the effect of reducing accident
rates while limiting advance rates. The
figure of 1% for the annual increase
in advance rates was supported by a
paper on advanced rates in tunnel construction which was presented at the
The Savio tunnel in Helsinki Finland with an Atlas Copco Boomer XL4 C and COP 3038 rock drills.
Excavating a wider tunnel than had been specified speeded up completion.
150,0
1,20
1973
1998
100,0
1,00
2007
0,80
50,0
0,60
Year
0,00
Drilling
Charging
Ventilation
Scaling
Shotcreting
Mucking
Bolting
Fig 1: The tunnelling cycle with various sequential operations at the tunnel face, with hours spent per metre of advance.
Fig 2: Accident rates in Swedish underground mines 19492007. Thanks to safety legislation and technological innovations, there has been a steady decline in accident
rates in underground operations over the years. Progress in reducing the overall tunnelling cycle time however, has been more limited (Data courtesy of SveMin).
200
175
150
125
100
75
50
1998
2007
1,01
0,07
0,14
0,14
0,95
0,34
0,27
2,75
1,25
0,50
1,50
3,50
1,00
1,00
0,44
0,20
0,10
0,31
0,51
0,17
0,20
1954
1959
25
0
1949
26
1973
1964
1969
1974
Year
1979
1984
1989
1994
1999
2004
199
199
198
198
198
197
197
197
196
196
195
195
0,20
0,0
4
195
7
196
0
196
3
0,40
Number
accidents per million work ho
Hours spentof
/ metre
Talking Technically
0
1949
1954
1959
1964
1969
1974
Year
1979
Talking Technically
Length of rounds
Excavating drifts by drill and blast requires sequential operations at the tunnel face, each characterized by the mobilization and demobilization of gear,
the time allocated for which is practically the same, irrespective of the length
of the round.
By extending the round from 4 m to
5 m, some 90 minutes is saved over 20
m of tunnel. For a long tunnel project,
this time saving can become significant. To solve the problem of drilling
boltholes where the feed exceeds the
height and width of the tunnel, a telescopic feed can be employed.
support as is needed at the face. The contractor will then install the remaining
support well behind the face in order
to reduce the time of support activities
at the face, and advance as quickly as
possible.
Mine drifting is mainly carried out in
connection with mine preparation. The
variation in ground conditions is often
less than for a typical civil engineering tunnel project. Drifting runs in
parallel at many faces, and the aim is
not to advance a single face as fast as
possible, but to excavate each tonne as
economically as possible.
In this situation, it is cost effective
to install all the bolts and the shotcrete
needed for final support right at the face,
as this will mean savings in terms of
mobilization time and simplicity. It will,
however, hamper the advance rate of a
prioritized heading. To summarize, it
can be said that civil tunnel construction
is characterized by a high degree of flexibility. As a result, the full potential of
faster tunnelling can be achieved, whenever the right conditions present themselves.
Scaling
Scaling is where drifting and tunnelling
deviate most when it comes to performance. This is not surprising when considering the comparable variations in
rock quality.
In tunnelling, along with the roof and
walls, the tunnel face is also scaled in
90
80
70
60
meters / week
equipment used are the input parameters when establishing the most effective tunnel size in relation to excavation
speed.
For example, a single-track railway
tunnel has been completed in Helsinki,
Finland. The client requested a tunnel
8.8 m high and 6.6 m wide. On part of
the project, the contractor offered a tunnel that was 7.5 m wide instead of the
requested 6.6 m.
This design, with its larger cross section, meant that the tunnel could be completed earlier, and at a lower cost, because the loading of the blasted rock
could be done at a much higher rate in
a larger tunnel.
Another technique is to alter the shape
of the tunnel, when possible, to allow for
the loading of rock directly at the face.
An example of this is the asymmetric
tunnel being built at Sauda, Norway. The
offset shape of the tunnel allowed trucks
to be loaded with blasted rock directly
at the face, speeding up the entire working cycle. Increasing advance rates by
using an alternative tunnel profile is
something that should be easier to implement for mines than for civil engineering contractors because mines have
more freedom to decide the shape of
their drifts.
50
40
30
20
10
0
1975
1979
1983
1988
1995
2005
Gunnar Nord
Boltec LC bolting.
Support work
The tunnelbuilder tries to determine what
the most likely rock classes are for the
coming rounds, so that the tunnelling activities can be planned in an optimal way.
The aim is to put in just as much rock
Mining methods in underground mining
27
1984
1989
Raise Boring
Principles of raiseboring
Efficiency and safety
Raiseboring is the process of mechanically boring, drilling or reaming a vertical or inclined shaft or
raise between two or more levels.
Some 40 years ago, the worlds first
modern raiseboring machine was
introduced by the Robbins Company. It launched a revolution in
underground mining and construction, and the technique is now accepted as the world standard for
mechanical raise excavation. New
products from Atlas Copco, such
as the BorPak, concepts such as
automatic operation and computerization, and techniques such as
horizontal reaming, are creating
exciting new opportunities in the
underground environment. Atlas
Copco Robbins supplies the complete raiseboring package for all
situations, together with technical and spares backup.
Raiseboring concept
The raiseboring machine (RBM) is set
up at the surface or upper level of the
two levels to be connected, and a smalldiameter pilot hole is drilled down to
the lower level using a string of drill
pipes and a tricone bit. A reamer is then
attached to the drill string at the lower
level, and the RBM provides the rotational torque and pulling power to ream
back to the upper level. The cuttings
from the reamer fall to the lower level
for removal. Raise bore holes of over 6
m-diameter have been bored in medium
to soft rock, and single passes in hard
rock can be up to 1 km in length.
Advantages of raiseboring are that
miners are not required to enter the excavation while it is underway, no explosives are used, a smooth profile is obtained, and manpower requirements are
reduced. Above all, an operation that
previously was classified as very dangerous can now be routinely undertaken
as a safe and controlled activity.
Specific applications of bored raises
in mining are: transfer of material;
ventilation; personnel access; and ore
28
Raiseboring process.
Raise Boring
Overhead
clearance
for complete
derrick
extension
Boxhole boring.
Alternative boring
methods
Boxhole boring is used to excavate raises
where there is limited access, or no access
at all, to the upper level. The machine is
set up at the lower level, and a full diameter raise is bored upward. Stabilizers
are periodically added to the drill
string to reduce oscillation and bending
stresses. Cuttings gravitate down the
hole and are deflected away from the
RBM at the lower level.
Blind shaft boring is used where access
to the lower level is limited, or impossible. A down reaming system is used,
in which weights are attached to the
reamer mandrel. Stabilizers are located
above and below the weight stack to
ensure verticality of the hole. Cuttings
are removed using a vacuum or reverse
circulation system.
Rotary drilling is used for holes up
to 250 mm-diameter, and is similar in
concept to pilot hole drilling in that a bit
is attached to the drill string to excavate
the required hole size.
Down reaming involves drilling a
conventional pilot hole and enlarging it
to the final raise diameter by reaming
from the upper level. Larger diameter
raises are achieved by reaming the pilot
hole conventionally, and then enlarging
it by down reaming. The down reamer
is fitted with a non-rotating gripper and
thrust system, and a torque-multiplying gearbox driven by the drill string.
Upper and lower stabilizers are installed
to ensure correct kerf cutting and to reduce oscillation.
Pilot up/ream down was a predecessor of modern raiseboring techniques
using standard drilling rigs. Pilot down/
ream down, or hole opening, employs
a small diameter reamer to follow the
Raiseboring machine
The raiseboring machine (RBM) provides the thrust and rotational forces necessary for boring, as well as the equipment and instruments needed to control
and monitor the process. It is composed
of five major assemblies: the derrick;
the hydraulic, lubrication, and electrical
systems; and the control console.
The derrick assembly supplies the rotational and thrust forces necessary to
turn the pilot bit and reamer, as well as
to raise and lower the drill string. Baseplates, mainframe, columns and headframe provide the mounting structure
for the boring assembly. Hydraulic cylinders provide the thrust required for
lowering and lifting the drillstring, and
for drilling and reaming. The drive train
assembly, comprising crosshead, main
drive motor, and gearbox, supplies the
29
Raise Boring
Acknowledgements
This article has been prepared using
The Raiseboring Handbook, Second
Edition, researched and compiled by
Scott Antonich, as its main reference.
30
Mechanized Bolting
Mechanization stages
Various methods of mechanized bolting
are available, and these can be listed
under the following three headings.
Manual drilling and bolting
This method employs light hand held
rock drills, scaling bars and bolt installation equipment, and was in widespread use until the advent of hydraulic
drilling in the 1970s. Manual methods
are still used in small drifts and tunnels, where drilling is performed with
handheld pneumatic rock drills. The
bolt holes are drilled with the same
equipment, or with stopers. Bolts, with
or without grouting, are installed manually with impact wrenches. To facilitate
access to high roofs, service trucks or
cars with elevated platforms are commonly used.
Semi-mechanized drilling and
bolting
The drilling is mechanized, using a hydraulic drill jumbo, followed by manual
installation of the bolts by operators working from a platform mounted on the
31
Mechanized Bolting
Significant improvements
Quality of bolting
In 1992, it was reported that independent studies were indicating that as many
32
When Atlas Copco introduced its current series of mechanized rock bolting
units, a wide range of radical improvements was incorporated.
Based on the unique single feed system with cradle indexing, the latest mechanized bolting unit, MBU, is considerably more robust, and less sensitive to
falling rock, than its predecessor. Holes
are easy to relocate, and the stinger cylinder improves collaring and the ability
to install bolts under uneven, rugged roof
conditions.
Major re-engineering has resulted
in 30% fewer parts. Less maintenance
and stock inventory are required, and
high availability has been recorded.
Furthermore, the chain feeds used
in the new Boltec series feature an
automatic tensioning device, which
guarantees even and strong feed force
for the rock drill, while a stinger cylinder improves collaring and the ability
to work under uneven roof conditions.
The completely redesigned drill steel
support provides sufficient space for bolt
plates passing through, and facilitates
extension drilling.
The most outstanding benefit, however, is the computer-based Rig Control
System, RCS. This system, which has
already been successfully incorporated
Mining methods in underground mining
Mechanized Bolting
Screen installation
In Canadian mines the combination of
rockbolts and screen, or wire mesh, is
commonly used for rock support. Since
rock reinforcement is potentially one of
the most dangerous operations in the
work cycle, mechanized rockbolting
has become more popular. A Boltec MC
using RCS, equipped with screen handling arm, has been in use for a couple
of years at Creighton Mine installing
screen with split-set bolts.
In general, the screen is 3.3 m-long x
1.5 m-wide, and is installed in both roof
and walls, down to floor level. Typical
spacing of bolts is 2.5 ft. Three different types of bolts are used, depending
on rock conditions, and all bolting must
be done through the screen, with the exception of pre-bolting at the face. In
general, galvanized split-set are used
for wall bolting, while resin grouted
rebar or mechanical bolts are used in
the roof, and Swellex in sandfill.
Once the screen handling arm has
picked up a screen section and fixed
it in the correct position, the powerful
COP 1132 hydraulic rock drill quickly
completes the 35 mm diameter, 6 ft
and 8 ft holes. The bolting unit remains
firmly fixed in position after the hole
is drilled, and the cradles are indexed,
moving the bolt, with plate, into position. The bolt feed, combined with the
33
Mechanized Bolting
impact power from a COP 1025 hammer, is used for installing split-set bolts.
The complete rock reinforcement job is
finished in just a few minutes.
Cabletec
Boltec MC flexibility
The Boltec MC delivered to the Creighton
mine is capable of handling several types of bolts: split-set, mechanical anchors, resin grouted rebar and Swellex.
The switch of accessories between different bolt types takes 5-10 minutes. To
minimize water demand during drilling, water mist flushing is used. The
Boltec MC can also be equipped with a
portable operators panel connected by
a 50 m-long cable.
Cartridge shooting is remote controlled for the Boltec MC, and up to
80 cartridges can be injected before
refilling is needed. A unique feature
is the possibility to use two different
types of cartridges, with fast or slower
curing times, housed separately in the
dual cartridge magazine. The operator can select how many cartridges of
each type to inject into any hole. For
instance, he can inject two fast curing
cartridges for the bottom of the hole,
and follow up with slower-curing
cartridges for the rest of the hole, all
without leaving his operators panel!
Simba
Cabletec drilling and installing cablebolts upwards, and Simba drilling blast holes downwards at Kemi mine.
13.9 m
Width:
2.7 m
Height:
3.3 m
Conclusion
Rock support, including scaling, bolting, screening, and cable bolting, is still
the bottleneck in the working cycle in
underground mining and tunnelling
applications. Clearly, any reduction in
the time required to install the necessary support has a direct impact on the
overall cycle time, and consequently the
overall productivity and efficiency of
the operations. The fully mechanized
bolting rig of today, incorporating all of
the benefits of modern computer technology, constitutes a major leap towards
improved productivity, safety and operator environment.
steep Mining
Long-hole
drilling and
blasting
Drill
access 1
Stope
Drill
access 2
Blasted ore
Undercut fan
blasting
Draw point
Loading
crosscut
Transport drift
Long-hole
drilling and
blasting
Stope
Blasted ore
Undercut
Transport drift
Draw point
Loading
crosscut
35
steep Mining
Raise
Timbered manway
(also ventilation)
Ore left in stope
Transport drift
Bighole stoping
Bighole stoping is an up-scaled variant
of sublevel open stoping, using longer,
larger-diameter DTH blastholes, ranging from 140 to 165 mm. Blast patterns
are similar to SLOS, but with holes up
to 100 m-long. A pattern with 140 mm
blastholes will break a rock slice 4 mthick, with 6 m toe spacing. DTH drilling is more accurate than tophammer
drilling, allowing the vertical spacing
between sublevels to be extended, from
40 m with SLOS mining, to 60 m with
bighole stoping. However, the risk of
damage to the rock structures has to be
taken into account by the mine planners, as the larger holes contain more
explosives.
Shrinkage stoping
Drill
overcut
Crater
blasting
charges
Primary
stope no1
in production
Loading draw
points
36
steep Mining
Ventilation tube
Hydraulic
sandfill
Ramp
Hydraulic
sandfill
Ramp
steep Mining
Caved
hanging wall
Production =
Blasting and
loading
Sublevels
Drilled
Charging
Footwall drift
Long-hole
drilling
Ore pass
Development of
new sublevels
Haulage level
Sublevel caving
Sublevel caving (SLC) adapts to large
orebodies, with steep dip and continuity
at depth. Sublevel footwall drifts have to
be stable, requiring occasional rockbolting
77% Ore
33% Waste
100
80
60
40
Dilution
entry
point
20
20
40
60
Ore + Waste
38
and safety, there is a trend towards replacing cut and fill mining with bench
stoping and fill, as at Mt Isa, Australia,
and towards open stoping with paste
fill, as at Garpenberg, Sweden.
80
100
120 %
Typical ore/waste
ratio during
a mucking cycle.
steep Mining
Block caving
Block-caving is a large scale production
mining method applicable to low grade,
Undercut
level
Drawbells
Pro
duc
tion
leve
Ven
lev tilatio
e
n
Pic l
k
lev hamm
el
e
Ore
pas
Picking
hammer
age
ul
Ha
el
lev
Hans Fernberg
39
flat Mining
Vertical benching
Pillar
00
Pillar
tlas
A
D
ock
co R
rills
20
AB,
Cop
large thickness, also to inclined deposits with larger thickness. Mining the
orebody creates large openings, where
trackless machines can travel on the
flat floor. Orebodies with large vertical
height are mined in horizontal slices,
starting at the top and benching down
in steps.
Post room and pillar applies to inclined orebodies, of dip angle from 20
to 55 degrees, with large vertical height,
where mined out space is backfilled.
The fill keeps the rock mass stable,
and serves as the work platform while
mining the next ore slice.
Step room and pillar is an adaptation
of trackless mining to orebodies with
too steep a dip for rubber-tyred vehicles to operate in a regular room and
pillar layout. Haulage drifts and stopes
are therefore angled diagonally across
the dip, to create work areas with level
floors off which trackless equipment
can work. Mining advances downward,
along the step room angle.
Ore production in flat room and pillar uses the same drill/blast techniques
as in normal drifting. Where geological
conditions are favourable, large-capacity
drilling rigs and loaders can be used.
High orebodies are mined in slices,
starting at the top, rockbolting the roof
from each bench. Standard crawler rigs
are used for drilling vertical holes and
conventional bench blasting. Horizontal
drilling and flat benching is a more practical alternative, using the same drilling
equipment.
The blasted ore is loaded using
diesel or cable-electric LHD machines,
and, where height permits, dump trucks
may be used between stope and dump.
In thin orebodies, loading points may
be necessary for transferring ore from
loader to hauler. As all activities are carried out on one or very few levels covering
a large area, there are many faces available at any time, so high equipment utilization is possible.
Post pillar
Post pillar mining is a crossbreed of room
and pillar and cut and fill mining. Post
pillar mining recovers the mineralization in horizontal slices, starting from a
bottom slice, advancing upwards. Pillars
are left inside the stope to support the
Mining methods in underground mining
flat Mining
t
Pos
ar
Pill
oR
opc
sC
tla
A
rills
D
ock
AB,
200
Longwall mining
Stope mined
tlas
co
Cop
k
Roc
000
B, 2
ls A
Dril
1
2
3
4
Numbers indicate
sequence of extraction
flat Mining
Complete package
Hanging wall
(The Venstop formation)
e
Strik
p
Di
Limestone
(The Steinvika formation)
cro
ssc
ut
h
benc
h
benc
ben
chin
g
ben
chin
g
Hor
ison
approx. 40 m
cro
ssc
ut
drift
tal p
illar
Foot wall
(The Fossum formation)
Dip
13 -
drift
8m
20 o
Hans Fernberg
Slashing holes
Blasting barricade
Transport
drift
Pillars of
timber/concrete to
support roof
At
las
Co
pc
oR
oc
kD
rill
sA
Scraper
B,
20
00
Scooptram ST600LP.
42
Backfilling
A.
Empty stopes are frequently backfilled as a means of providing support for future mining. Other than
its own body weight, backfill is a
passive support system that has
to be compressed before exerting
a restraining force. Backfill material is normally generated by the
mine as waste rock underground,
or as tailings from the surface concentrator, so backfilling may serve
a secondary purpose as a means
of disposal of otherwise useless
byproducts. The optimum backfill method is clearly related to the
mining method. Costs of backfill
typically range between 10-20% of
mine operating cost, of which cement represents up to 75%. Paste
fill is gaining in popularity because
it uses unclassified tailings and
less water, but the capital cost of
a paste fill plant is approximately
twice the cost of a conventional
hydraulic fill plant of the same
capacity.
Drift 1
Fill
Drift 3
Fill
Drift 4
B.
Drift 1
Fill
Drift 3
Drift 2
Fill
Fencing
Fencing
C.
Drift 1
Fill
Drift 3
Drift 2
Fill
D.
Drift 1
Cemented
Fill
Functions of backfill
The original function of backfill in hard
rock mines was to support rock walls
and pillars, and to provide a working surface for continuing mining. This was
initially accomplished by rock fill, and
more often in the present day by hydraulic fill.
If 3-4% of cement is added to a hydraulic backfill of concentrator tailings,
and this is topped off in the stope with
a 10% mix, a smooth and hard surface
results. This is useful for mechanized
removal of broken ore from the subsequent mining operation, and reduces
dilution from the fill.
Backfill also affords the opportunity
for more selective mining and better recovery of ore and pillars, thereby increasing both mine life and total return
on investment.
Other functions of backfill are the
prevention of subsidence, and better
control over ventilation flow through
Drift 2
Fill
Drift 3
Drift 2
Cemented
Fill
the mine workings. Cemented hydraulic fill (CHF) or paste backfill may
also be used to stabilize caved areas in
the mine. Backfill is also considered an
essential tool to help preserve the structural integrity of the mine workings as
a whole, and to help avoid stressing
ground to the point where rock bursts
take place.
Backfilling
ROCK fill
CAF fill
ROCK fill
ROCK fill
Unmined
Unmined
Unmined
CAF fill
Unmined
Unmined
Unmined
Unmined
Unmined
Unmined
Designed stopes
Unmined
CAF fill
Primary
Secondary
Tertiary
Primary
Secondary
CAF fill
Hydraulic fill
Originally, backfill comprised waste
rock, either from development or hand
picked from broken ore. Some larger
mines in the US quarried rock and gravitated it down fill raises to the mine
workings.
Nowadays, rock fill is used for filling secondary and tertiary stopes,
and is usually a convenient and economic means of disposal for waste from
development.
Hydraulic fill
Low cement
content
Slice 1
High cement
content and
reinforcement
Slice 2
Slice 3
Slice 4 Face 1
44
Face 2
The first hydraulic fills were composed of concentrator tailings that would
otherwise have been deposited on the
surface. The mill tailings were cycloned
to remove slimes so that the contained
water would decant.
This fill was transported underground as slurry, composed of around
55% solids, which is the typical underflow for thickeners and is the pulp density normally used for surface tailings
lines.
When the grind from the mill was too
fine for decanting in the stopes, alluvial
sand was employed instead of tailings.
Particles of alluvial sand are naturally
rounded, enabling a higher content to
be pumped than for hydraulic fill made
from cycloned tailings. This type of fill
is commonly referred to as sand fill.
Many mines still employ non-cemented
hydraulic fill, particularly for filling tertiary stopes.
The quantity of drain water from hydraulic backfill slurry containing 70%
solids is only a quarter that resulting
from a 55% solids mix.
The porosity of hydraulic backfill is
nearly 50%. It may be walked upon just
a few hours after placement, and will
carry traffic within 24 hours.
Mining methods in underground mining
Backfilling
Cyclone
Thickener
Vacuum filter
Mixer
Planning considerations
Because the density of hydraulic fill is
only about half that of ore, a supplementary fill material will be needed when
less than half of the tailings can be recovered from the mill circuit.
When planning a hydraulic fill
system, a major consideration is water
drainage, collection and disposal, particularly on deep mines. Getting large
volumes of water back to surface can
be a costly exercise, and installing the
infrastructure may be difficult, expensive and time consuming.
Portland cement added to hydraulic
fill as a binder also adds strength, and
this system of fill in normal and high
density is employed at many mines
around the world. A portion of the
cement may be substituted using fly
ash, ground slag, lime or anhydrite.
If cement is added in the ratio 1:30,
the backfill provides better support for
pillars and rock walls. If the top layer is
then enriched at 1:10, the backfill provides a smooth and hard surface from
which broken ore can be loaded and removed. Addition of cement reduces ore
dilution from the fill and facilitates selective mining and greater recovery
from both stopes and pillars.
Water decanted from cemented fill
has to be handled appropriately to avoid
cement particles reaching the ore passes
Paste fill
Paste fill originally used non-cycloned
mill tailings mixed with cement at the
stope. Coarse tailings permit a very high
solids content of up to 88% to be pumped at high pressure, and high setting
strengths were achieved. Paste is currently used as a replacement for hydraulic fill, with the cement added at surface. It exhibits the physical properties
of a semi-solid when compared to highdensity fill, which is a fluid.
Because the slimes fraction of the
tailings forms part of the mix, cement
always needs to be added into paste fill,
with 1.5% as the minimum requirement
to prevent liquefaction. Very precise control of pulp density is required for gravity flow of paste fill, where a 1-2%
increase can more than double pipeline
pressures.
Hans Fernberg
45
rock reinforcement
Swellex
The Swellex concept entails that the rock is secured by immediate
and full support action from the Swellex bolts. The moment the
Swellex bolt is expanded in the hole, it interacts with the rock to
maintain its integrity. The quality of the bolt installation is automatically confirmed when the pump stops, and is independent of
rock mass conditions or operator experience. Controllability means
safety! The Swellex rockbolts are designed to optimize the effectiveness of each bolt, so the bolting operation matches the required
safety levels as planned by the engineers. See pictures to the left.
Roofex
Roofex features a high quality steel bar inside a smooth plastic sheathing which is fixed inside the borehole with cement or resin grout.
The bolt also has an energy absorber which functions as a sliding
element over the steel bar. This allows the bolt to extend outwards
during sudden displacements such as rock burst or seismic events while
still providing constant load capacity. This capability makes the Roofex
rock bolt especially suitable for developing new, deep underground
excavations in poor quality rock or in areas where rock burst or seismic events are frequent. The bolt can be produced in standard lengths
typically used in mining and tunnelling, and the displacement capacity can be pre-selected during manufacture. See picture below.
Mathias Lewn
Pre-calculated
maximum
deformation
Pre-calculated
maximum
deformation
1.
Roofex at
installation
2.
Energy
absorbing
phase
3.
Roofex at
max load
and max
deformation
Energy absorber
(a sliding element)
46
Garpenberg, Sweden
0Z
Garpenberg North
Gruvsj shaft
Capacity: 450 000 tpa
Smltarmossen
Shaft
Capacity: 850 000 tpa
Dammsjn
0Z
Dammsj Agmin
?
400 Z
Lappberget
?
500-785 Z
Finnhyttan
500800 Z
Tyskgrden
7001000 Z
800 Z
Kaspersbo
910 Z
Dammsjn Kvarnberget
2000 Y
Gransjn
800 Z
870 Z
925-1100 Z
1200 Z
1600 Y
400 Z
2400 Y
2800 Y
3200 Y
1000-1300 Z
11001400 Z
3600 Y
4000 Y
4400 Y
1200 Z
4800 Y
5200 Y
Production levels
Potential areas outside ore reserves 2005-01
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
Garpenberg, Sweden
Higher output
to the 910 m level. In 1998-9, it was extended to the 1000 m level, increasing
the overall length to 8.7 km.
To increase hoisting capacity at the
Garpenberg mine, the new Gruvsj production shaft was completed in 1997 and
the original shaft was converted for personnel and materials hoisting. With a
hoisting capacity of 450,000 t/y, the newer shaft connects with a ramp accessing the Kanal and Strand orebodies.
The present operating area extends
approximately 4.5 km SW to NE from
the original shaft to the Gransjn mining section.
Concentrate production
Upgraded in the early 1990s, the concentrator yields separate zinc, lead, copper and precious metals concentrates.
The zinc and lead concentrates are
trucked to Gvle harbour and shipped
either to Kokkola in Finland or Odda
in Norway. Copper and precious metals
concentrates are railed to the Rnnskr
smelter in Sweden. Since 1957, Boliden
has milled over 20 million tonnes of ore
at Garpenberg.
While the new shaft raised hoisting
capacity, and ramp extension accessed
new ore in the North mine, metals pro48
New reserves
Probably the most significant event at
Garpenberg during the period of decline
was the discovery in 1998 of a new orebody between Garpenberg North and
Dammsjn, named Lappberget. This encouraged the company to start development in 2000 of an approximately 3.0
km long drift to connect the 900 m level
at Garpenberg North, first to Lappberget
for exploration access, and thence to the
ramp at the 800 m level at Garpenberg.
During 2001, Boliden started core drilling at the 800 m and 1000 m levels in
Lappberget, and by February, 2003 was
able to start mining ore from the new
Garpenberg, Sweden
896 Z
Mined in
Central Zone
10
0
11
3m
916 Z
Possible
sequence
10
11
6
956 Z
17.5 m
Drawpoint
spacing
Sublevel stoping at
Lappberget
The geological and geotechnical characteristics of significant portions of the
newly-discovered orebodies allow mining using more productive longhole
methods instead of cut-and-fill. Lappberget ore, for instance, can be 60 m
wide through considerable vertical distances, and has proved to be suitable for
sublevel stoping using a system of primary and secondary stopes progressing
upwards. Primary stopes are 15 m wide
and 40 m high and filled with paste
made from concentrator tailings mixed
with about 5% cement. The 20 m wide
secondary stopes are filled with development muck without cement. High precision drilling is necessary to get optimum ore recovery and fragmentation.
This mining method can possibly be
used in parts of the Kaspersbo orebody,
if rock quality is high enough. This will
help with cost control, which is crucial
for mining in Sweden. With Lappberget
alone containing 5.46 Mt of the current
reserves, grading over 7% zinc and 2.6%
lead, plus silver and gold, it is no surprise that present development activities
focus on using longhole-based production from these orebodies to raise total
metal-in-concentrate output. Presently
eight orebodies are being exploited.
Garpenberg has generated a strategic
plan for 20062019 allocating SEK 1
billion for developing Lappberget. The
overall programme includes: increasing concentrator capacity to 1.2 Mt/y;
designing and building a paste fill production/distribution system; and starting longhole drilling. This latter project
Primary stope:
15 m wide x 40 m high
Paste fill
Note:
N
Note
Secondary stope:
20 m wide x 40 m high
Rock fill
fill
How
Ho
ow this
o
t
hole must be designed to just
miss
m
the
t drift below to break properly
4
996 Z
Rill mining
A special mining method known as rill
mining has been developed for excavating the Tyskgrden orebody. The orebody is relatively small and large quantities of development muck have to be
accommodated underground as hoisting facilities are used for ore only.
The method can be described as a
modified sublevel stoping with successive back fill as mining is progressing.
The 10 m wide cut-off slots are drilled
across the orebody using up-holes and
49
Garpenberg, Sweden
Approx. 15 m
m
70 m
n
h fa
eac
t
s
s in
bla
ole
ne
no
m
ns i
1.8
3 fa
Waste
8h
Blasted ore
Approx. 15 m
Max
2m
70
45
ore haulage to surface possible. And, although flotation capacity has been improved, concentrator throughput is now
limited to the same sort of tonnage by
grinding mill capacity. Assuming demand for Garpenberg concentrates increases in the near term, it will be necessary for New Boliden to decide whether
to increase hoisting capacity. Developing
the now-available reserves for higher
long-term production using additional
hoisting and processing capacity might
double the amount of investment initially planned.
50
Garpenberg, Sweden
develop the most efficient round compatible with the new parameters. The
generated drill plan is automatically entered into the Boomer L2 C ABC Regular standard drilling system, and the
operator can start drilling. While drilling, each completed hole is logged, and,
if the Measure While Drilling (MWD)
option is activated, the drilling parameters along the hole are recorded. All
of the data is logged on the PC card for
off-line processing in the Tunnel Manager
support program, and is then transferred
to the mine database. As a result of the
Drill Plan Generator and ABC Regular,
Garpenberg North increased the size
of the production rounds from 400 t
to 600 t, reduced drilling time from 5
to 3 h/round, reducing costs of explosives, scaling and rock support and,
most important, minimizing ore dilution. Garpenberg now has one Rocket
Boomer L2 C30 rig with COP 3038
rock drills and one Rocket Boomer L2 C
with the COP 1838, as well as the Rocket
Boomer 352S.
Mine navigation
The availability of orebodies at Garpenberg suitable for mining with longhole
production drill rigs led to a further collaboration. Having already transferred
RCS technology to the Simba longhole
drill rigs, Atlas Copco provided the mine
with a Simba M7 C that is additionally
able to use new software for precision
longhole drilling. This utilizes Garpenbergs mine coordinate reference, mapping and planning system in a similar
way to the software developed for the
Rocket Boomer L2 C units.
Using a PC card, the Mine Navigation
package can effectively integrate the
Simba RCS with the mine co-ordinate
reference system, allowing the operator
to position the machine at the correct
vertical and horizontal coordinates in
the drilling drift for drilling planned
longhole fans in precisely the intended
place. Using the drill plan supplied by
Microsystem (or, in other mines, the
Ore Manager package) to the Rig Control System, the operator can drill to
the exact x, y and z positions prescribed
for each hole bottom. Just as the Rocket
Boomer rigs can use the MWD system
while face drilling, so the Simba can
Reference line
X
Y
Z
use Quality Log to record drilling parameters and compare the planned and
actual result, allowing holes to be redrilled if necessary. This new technology will help Garpenberg to optimize
economy and productivity when applying long hole drilling mining methods.
The target for 2007 was to mine
about 600,000 t of ore by cut-and-fill,
300,000t by sublevel stoping, 150,000t
by rill mining and 150,000 t by crown
pillar removal. Further ahead, sublevel
stoping is expected to contribute up to
50% of total mine production. However,
at present this mining method is completely new to the mining teams at
Garpenberg, and they have just started
the process of getting acquainted with
long hole drilling methods.
Longhole drilling at
Lappberget
After perfecting its longhole drilling
techniques at its Tyskgrden orebody,
the Garpenberg mine began open stoping of the Lappberget orebody using
Simba M6 C and Simba M7 C production drill rigs. These are drilling primary and secondary stopes, 10 and 15 m
wide respectively, and 20-25 m high.
At one of the primary stopes, at the
1060 level, the Simba M7 C has been
drilling up-hole fans using T38 rods
since late 2006. The 70 mm holes range
in length up to 20 m. The Mine Navigation system is used to position the rig
Acknowledgements
This article is based upon an original
report by Kyran Casteel. Atlas Copco
is grateful to the mine management at
Garpenberg for their assistance with
site visits, and in particular to Tom
Sderman for comments and revision.
51
Garpenberg, Sweden
Headframe at Garpenberg.
52
Zinkgruvan, Sweden
Methodology
Until the mid 1980s, upwards cut and
fill was the dominant mining method.
However, when mining began at the
650 m level in Nygruvan, the first problems with rock stress occurred, resulting
in the need for increased rock reinforcement. When mining reached the 566 m
level, a borehole camera survey revealed
a roof split 6 m above the stopes, causing abandonment of cut and fill methods on safety grounds.
Benching methods were introduced,
and have been under constant development since, primarily because of high
rock stress. Using benching, no working place need be developed wider than
7 m.
Over the years, benching has developed from longitudinal bench and fill.
The mined out bench is backfilled with
hydraulic fill before mining the next
bench above. Vertical pillars in the ore
are left to stabilize the surrounding
rock.
Open stoping
Development continued towards sublevel open stoping, which is a larger
scale stoping method than longitudinal
bench and fill, with improved rock stress.
Zinkgruvan, Sweden
Burkland stopes
Earlier, a study of the new copper orebody had recommended that longhole
open stoping and paste backfill should
be used when the width of the copper
mineralization reaches up to 40 m. The
Stoping sequence.
Cor/slot
50 m
Rib
pillar
Ore outline
10 m
Rib
pillar
Rib
pillar
Drill level
(for below)
Development level
(for above)
Cable bolts
11
10
45 m
Drawpoint level
(shown in plan view)
54
Zinkgruvan, Sweden
Paste fill
Hydraulic fill was introduced to Zinkgruvan in the early 1970s when the new
mill was built, and was used successfully for many years. However, during
the transition to sublevel open stoping,
difficulties arose in sealing the open
stopes when using hydraulic fill. The
bulkheads could not be sealed against
the cracked rock in the draw points, and
there was also seepage through cracked
pillars. Because of the difficulties of
managing the fill, certain stopes have
not been filled, as the risk of fill collapsing is greater than the chances of
a hanging wall collapsing in the open
stopes.
Alternatives that were studied included hydraulic fill, with cement for about
50% solidity; paste fill, with cement for
70-76% solidity; and high-density fill,
with cement for greater than 76% solidity. Paste fill with cement was selected
for longhole open stoping with primary
and secondary stopes. Investments required in the paste plant, and for pipe
installations underground, reached
about 45 million SEK. Golder Paste Technology, together with Zinkgruvan personnel, handled the design, construction
and building.
Primary stope
Secondary stope
Slump
Nygruvan
Burkland
4 % cement
6 % cement
1.5 % cement
2 % cement
150-180 mm
200-250 mm
ore. The paste fill is horizontally transported 1.4 km in order to reach these
Ore outline
S
P = Primary
S = Secondary
Ore drive
P
S
Ore shaft
P
S
Waste shaft
Ventilation
Transport drift
Ramp
Footwall drive
55
Zinkgruvan, Sweden
Rock reinforcement
Lower development
In order to mine below the 800 m level,
the mine uses three Kiruna Electric
trucks for ore and waste haulage to the
main crusher. A Simba M4C longhole
drill rig is used on production, drilling
up to 40 m long x 76 mm or 89 mm
diameter blastholes. The machine produces some 50,000 drillmetres/year,
while an older Simba 1357 drills a similar number of metres in the 51-64 mm
range. The mine is so impressed with
the stability of the Simba M4 C rotation
The mine installs up to 20,000 resin anchored rockbolts each year, and, having
upgraded its production process, found
that bolting became the new bottleneck.
After prolonged testing of the latest
Atlas Copco Boltec LC, they ordered
two units.
Using these machines, the working
environment for the bolting operatives
has improved immeasurably, since the
continuous manual handling of resin
cartridges has been eliminated. The
Boltec LC is a fully mechanized rockbolting rig, with computer-based control
system for high productivity and precision. The Zinkgruvan models feature a
new type of magazine holding 80 resin
cartridges, sufficient for installation
of 16 rockbolts. It is equipped with a
stinger, which applies constant pressure
to keep it stable at the hole during the
entire installation process. The operator
can select the number of resin cartridges
to be shot into the hole, for which the
blow capacity is excellent.
The Rig Control System (RCS) features an interactive operator control panel, with full-colour display of the computer-based drilling system. Automatic
functions in the drilling process, such
as auto-collaring and anti-jamming protection, as well as improved regulation
of the rock drill, provide high performance and outstanding drill steel economy. There is integrated diagnostic
and fault location, and a distributed hydraulic system, with fewer and shorter
hoses for increased availability. Data
transfer is by PC-card, which also allows
service engineers to store optimal drill
Mining methods in underground mining
Zinkgruvan, Sweden
Crown pillar
4.5 m
8-15 m
Typical
cable
bolting
51 mm
drill bit
Production
drilling
74 mm
drill bit
Drawpoint level
New facilities
Opening slot
Opening raise
Top view
Front view
57
Zinkgruvan, Sweden
Pioneering partnership
In a pioneering deal with Atlas Copco,
the mine has undertaken an eight year
agreement in which the mines production fleet will be re-purchased by Atlas
Copco and then leased back to the mine.
The mine will hand over the running
of the eight rigs in order to focus on its
58
effective way, and the mine is ideally positioned to maintain maximum output.
From the mine point of view, maintenance of their equipment requires specialist competence, and through the
agreement with Atlas Copco, they have
constant back-up. If they have a breakdown, they can get production up and
running again quickly with a reserve rig
and avoid any losses in productivity.
Mines, in general, are becoming more
aware of the benefits that financing can
bring, giving them control over the costs
associated with their production fleet,
assisting long-term planning and forecasting.
Acknowledgements
This article is based on a paper written by Gunnar Nystrom. Atlas Copco
also gratefully acknowledges the inputs
of Hans Sjoberg and Conny Ohman,
both of Zinkgruvan Mining.
Kiruna, Sweden
1910
1910
1920
1920
Niv m
1900
1930
1930
1940
1940
1950
1950
1960
1960
142
1965
1965
1970
1970
230
275
320
420
1980
1980
540
1990
1990
Skip hoisting
2000
2000
2005
2005
Sea level
Skip hoisting
Ore buffer
pockets
Exploration drift
1060 m
740
775
1045
Crusher
1175
1365
Crusher
Optimum
techniques
For more than 40 years, the miners
of LKAB in the far north of Sweden
have been working to get as close
as possible to the optimum underground mining technique. At
Kiruna, in what is the world's largest underground iron ore operation, many milestones have been
reached and passed. Now another
is on the horizon as the mine takes
new steps to go deeper and expand. Sister mine Malmberget is
also expanding output, albeit on
a lesser scale. Key to both is a
collaboration with Atlas Copco
that is providing specialized drilling equipment together with the
means of maintenance.
Continuous quest
The Swedish state-owned mining company LKAB is on a continuous quest
for the most favourable balance possible
in the relationship between ore recovery, waste dilution, overall costs and
productivity. Much of the development
work done here has been carried out in
close cooperation with equipment suppliers, including Atlas Copco.
LKAB's relationship with Atlas Copco
began in the early 1960s, with mechanized drilling equipment which was the
predecessor of todays automated longhole production drilling system.
In 1997, Atlas Copco supplied LKAB
with four Simba W469 drill rigs equipped with a PLC control system. This
Kiruna, Sweden
Increasing outputs
60
From their control rooms, the LKAB operators run several drill rigs out in the production areas via remote control. The
fans are drilled forwards, 10 degrees
off vertical, generally with a burden of
3 m, although a 3.5 m burden is used
in some parts of the Malmberget mine.
Pumped emulsion and Nonel detonators
are the standard explosives.
Kiruna mine is aiming to achieve one
million metres of production drilling in
2007. Malmberget, on the other hand, is
going for 0.6 million metres. But both
will need to increase their capacity in
order to maintain and increase the buffer
between production drilling and loading.
It was in 2005 that LKAB took the
decision to install three Simba W6 C
units which are modified versions of the
Simba L6 C. Two of these are designed
for optimized production drilling at
Kiruna Mine with the Wassara water
hammer.
The third, a Simba W6 C Slot, was
redesigned for optimized up-hole slot
drilling in the Malmberget mine. This
rig has the ability to drill production
holes around the slot, with the added
benefit of drilling parallel rings from the
same set-up with a burden of 500 mm.
The criteria from LKAB were high
productivity, efficiency and accuracy.
The rigs in the Kiruna mine will have
to drill 60 m-long holes in order to meet
future targets.
Such long holes have to be very
straight, and with the new rigs LKAB
has high expectations for both production rates and precision, with the flexibility of being able to run the rigs
manually as well as automatically. The
Wassara hammer has the advantage that
it does not leak oil into the environment.
Mining methods in underground mining
Kiruna, Sweden
38
43
1048 m
34
29
25
20
16
11
7
2
Alternative configurations
The rigs drill alternative configurations
with holes 15-58 m long. The fans are
spaced at three metre intervals, and any
deviation of more than 2% might cause
the fans to overlap. The average penetration rate is 0.65 m/min over the entire
hole, which can be compared to tophammer drilling where the penetration
The Wassara W 100 hammer on the Simba W6 gives good penetration and, as it is water-powered, does not release any oil into the air.
61
Kiruna, Sweden
Service agreements
Both LKAB mines have full service
agreements with Atlas Copco, who provide continuous preventive maintenance
for their fleet of 20 rigs. Under the terms
of the agreement, Atlas Copco runs a
thorough check on each rig at the rate of
one per week. The agreement, which is
based on the number of metres drilled,
also includes the supply of all spare
parts. Only genuine Atlas Copco parts
are used on contract maintenance,
guaranteeing longer service life and
greater availability.
The availability target is 92%, and
penalties are payable on underperformance, with bonuses awarded if the
targets are exceeded. LKAB is pleased
with the agreements and the way they
have been designed, feeling they can
let go of the maintenance responsibility
and concentrate on drilling.
Many changes have been introduced
to ensure communication between mine
and manufacturer on a regular basis,
resulting in a mutual approach to problem solving with a focus on proactive
and preventive maintenance.
One of the most important changes
was to reorganize the service intervals
62
Acknowledgements
Atlas Copco is grateful to the managements of Kiruna and Malmberget mines
for their assistance in the production of
this article.
All on the same team: From the left, Robert Wetterborn, Construction Supervisor, Mining Dept. at LKAB, Patrik
Kansa, Atlas Copco Service Manager and Roger Lrkmo, Production Manager, Production Drilling at LKAB.
Kemi, Finland
Production control at
Kemi chrome mine
Intelligent mining
The large chromite deposit being
mined by Outokumpu at Kemi,
Finland has a lower than average
Cr 2O3 content of about 26%, so
chromite and ferrochrome production technology has had to be continuously upgraded to remain competitive.
The Intelligent Mine Implementation Technology Programme of
14 projects achieved real time control of mine production in precise
coordination with the needs of the
mineral processing plant and the
ferrochrome smelter. The system
utilizes a fast, mine-wide information system that can help optimize financial results for the whole
operation. Computerized drilling
with Atlas Copco Rocket Boomer
and Simba rigs, accurate coring
with Craelius rigs, reliable rock
reinforcement with Cabletec and
Boltec rigs with Swellex bolts, and
the dependability and longevity of
Secoroc drilling consumables support this unique mine strategy. An
automated Scooptram ST14 has
been evaluated for backfilling,
with good success. The result is
cost-efficient, integrated production, on a model which may form
the basis of the next generation of
mining techniques.
Introduction
Outokumpu is one of the worlds largest
stainless steel producers, accounting for
about 8% of global stainless slab output,
and a similar share of cold rolled production. These are hugely significant
proportions of a market that has risen
by an average of 5.5% per annum over
the last 20 years, and is currently enjoying 7% growth.
Mainstay of the Outokumpu strategy
is its highly cost-efficient fully integrated mine-to-mill production chain
in the Kemi-Tornio area of northern
Finland. An ongoing investment programme of EUR1.1 billion will expand
started in 2003 at 150,000 t/y, and production will increase to the planned
level of 1.2 million t/y by 2008.
Reserves
The Kemi deposit is hosted by a 2.4 billion year old mafic-ultramafic layered
intrusion extending for some 15 km
north-east of the town itself. The
chromite-rich horizon appears 50-200
m above the bottom of the intrusion,
and has an average dip of 70 degrees
63
Kemi, Finland
Underground infrastructure
The main decline starts at a portal in
the footwall side of the pit, at about 100
m below the rim. The decline is mostly
8 m wide x 5.5 m high, to accommodate passing vehicles. It descends at
1:7 to a depth of 600 m at the base of
64
Kemi, Finland
Underground production
Trial stopes in three areas accessed
from the 275 m and 300 m levels were
mined to determine the parameters of
the bench cut-and-fill technique to be
used. These had a width of 15 m, and
were 30-40 m long, with 25,000-30,000
t of ore apiece. Both uphole and downhole drilling methods were tested, and
51 mm diameter downholes selected as
being the safest.
For production purposes, 25 m high
transverse stopes are laid out, with cable bolt and mesh support to minimize
Mining methods in underground mining
65
Kemi, Finland
The Scooptram ST14 during tests at Kemi Mine, trams automatically between loading and dumping.
The process is supervised from a remote control station.
A 3D impression of Kemi mine showing the open pit, the underground development and the orebodies.
66
Rock reinforcement
2.4 m long Swellex Mn12 bolts are
used for support in ore contact formations. These are being installed at a
rate of 80-120 bolts/shift using an Atlas
Copco Boltec LC rig, which is returning drilling penetration rates of 3.2 to
4 m/min. The Boltec LC rig, featuring
Atlas Copco Rig Control System, RCS,
mounts the latest Swellex HC1 pump,
for bolt inflation at 300 bar pressure,
and reports progress on the operators
screen.
The HC1 hydraulic pump is robust,
simple, and with low maintenance cost.
Coupled to an intelligent system, it reaches the 300 bar pressure level quickly,
and maintains it for the minimum time
for perfect installation. Combined with
the rigs RCS system, the pump can confirm the number of bolts successfully
installed and warn of any problems with
Mining methods in underground mining
Kemi, Finland
inflation. A series of slip-pull tests carried out throughout the mine proved the
strong anchorage capacity of Swellex
Mn12, both in the orebody and for
the softer talc-carbonate and mylonite
zone.
Cable bolting
Kemi installs some 80 km of cable
bolt each year using its Atlas Copco
Cabletec L unit, which is based on the
longhole production drilling rig Simba
M7, with an added second boom for
grouting and cable insertion. The Rig
Control System enables the operator to
pay full attention to grouting and cable
insertion, while drilling of the next hole
after collaring is performed automatically, including pulling the rods out of
the hole. The main benefit of the twoboom concept is to drastically reduce
the entire drilling and bolting cycle time.
Also, separating the drilling and bolting
functions prevents the risk of cement
entering the rock drill, thereby reducing service and maintenance costs.
Kemi tested the prototype Cabletec L
and eventually purchased the unit after
minor modification proposals. During
the testing period, where most holes
were in the 6 to 11 m range, the rig grouted and installed cables at rates of more
than 40 m/hour. The capacity of the unit,
which is governed by the rate of drilling, provided around 50 per cent extra
productivity compared with alternative
support methods.
The Cabletec L is equipped with a
COP 1838 ME hydraulic rock drill using
reduced impact pressure with the R32
drill string system for 51 mm hole diameter. The machine's cable cassette has
a capacity of 1,700 kg and is easy to refill, thanks to the fold-out cassette arm.
It features automatic cement mixing
and a silo with a capacity of 1,200 kg of
dry cement, which is mixed according
to a pre-programmed formula, resulting in unique quality assurance for the
grouting process.
67
Kemi, Finland
Acknowledgements
Atlas Copco is grateful to the mine and
concentrator management at Kemi for
assistance in producing this article.
68
Jelsava, Slovakia
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.
SMZs raw Jelava 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.
Geology
The Dbrava-Mikov orebody that SMZ
exploits is the largest of 12 significant
magnesite deposits in Slovakia. These
extend from Podrecany in the west to
Bankov, near Koice, in the east and were
all mined for varying periods during the
20th Century. The mineralization is part
of a magnesite belt extending from central Austria to the Slovakia-Ukraine border. Within Slovakia, the deposits occur
mainly in the Slovensk Rudohorie
mountains, and Jelava is in the deeply
dissected Revcka highland area of this
69
Jelsava, Slovakia
Milkov
Dbrava
Jedlovec
500 m a.s.
450 m a.s.
400 m a.s.
323 m
3
Main Level
220 m a.s.
5
4
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
3. Ore passes (raises 4. Re-fill raises 5. Inner pillar 6. Re-fill
diabase, comprises graphitic slate,
1,000 m-wide and 400 m-thick, but is
source of ferric magnesium, this being
bench-like dolomite, and the dolomite
irregular in shape and contains cavities
one reason why it is imported by conwhich hosts the magnesite. Graphitic
often filled with ochre. However, it is
sumers so far away. SMZ estimates a
slate also overlies the dolomite.
structurally sound, to the extent that it
reserve sufficient for 150 years mining
Magnesite formation has been dated
could be mined with pillar support and
at the present production rate of 1.2
at 320 million years and the mechanism
no rock reinforcement. The raw magmillion t/y.
is thought to have been hydrothermal
nesite analyses 36-44% MgO, 48-50%
alteration of a fine-grained CarboniCO2, 0.1-12% CaO, 0-2.3% SiO2 and
Room and pillar
ferous limestone bioherm. The orebody
3.2-6% Fe2O3. The specific mineralAround 35% of the ore is mined by the
is estimated to be 4,000 m-long,
ogy makes Jelava magnesite a unique
room and pillar method in blocks which
are up to 100 m-long, 50 m-high and 30
Sequence of room and pillar mining.
m-wide, with 10 m-wide pillars along
the short and long walls of the chamber,
and a crown pillar at the top. Within
2
these blocks, it is impossible to avoid
mining some lower grade material, and
this is stored in surface dumps.
4
Parallel uphole and inclined hole
drilling up to 30 m was initially used
3
for blasting the chambers, but the mine
later switched to fan drilling in order
to achieve better mining efficiency and
safety.
6
This method again allows the mining
of long, high blocks of magnesite up to
5
200 m x 300 m x 60 m, mined in up to
1
five ascending slices.
The technique provides much greater
1. Fresh air ventilation raises 2. Exhaust airways 3. Ore passes
stability in the rock mass because, not
4. Re-fill raises 5. Pillars 6. Re-fill
only are the rooms lower at 4.8 m to
70
Jelsava, Slovakia
Pillar
between
stopes
boundary
pillar
pe
n sto
Ope
t
scu
ros
c
g
ts
din t drif
r
loa
ith nspo
w
ar
tra
Pill and
rock drill. This rig achieved the expected performance improvement, and was
bought by SMZ, together with a Rocket
Boomer 281 and a Simba H357, for precise and rapid pillar recovery. The latter
unit was equipped with a COP 1838 rock
drill. Switching from pneumatic to hydraulic drilling using the two Rocket
Boomers increased overhand stoping
magnesite output by a factor of four.
In the overhand stoped sections muck
is loaded by a fleet of three LHDs and
two wheel loaders. The LHDs typically
Overhand stoping
Chamber and pillar mining has created
a huge void within the mine, now totalling 13 million cu m, and undercut sections of the hanging wall have collapsed
in places.
Studies resulted in an overhand stoping method being introduced in some
of the mining blocks above the 323 m
level from 1990 onwards, and this now
accounts for 65% of production.
By 1998, SMZ was looking to increase
production and productivity in the overhand stoping blocks. In consultation with
Atlas Copco, the mine trialled a Rocket
Boomer 282 equipped with a COP 1432
Mining methods in underground mining
71
Jelsava, Slovakia
Graphitic slate
Magnesite
Dolomite
Bench-like dolomite
Diabase
Ochre
Grade improvement
Secoroc equipment supplied through
ISOP is used for the Atlas Copco rigs
at Jelava. Despite the very abrasive
nature of the magnesite, bit life ranges
from 600 m to 1,500 m. The three
Rocket Boomers use 51 mm bits, and
the Simba H357 drills with 64-65 mm
bits. The mine does 80% of its blasting
with ANFO, and uses plastic explosive
for wet holes.
Of the annual mine production of
1.2 million t, around 1.16 million t is
magnesite, and concentrate output is
72
Atlas Copco
representation
Atlas Copco has a Customer Center in
Prague, serving the Czech Republic and
adjacent countries. In 1992 ISOP, based
at Zvolen in the centre of the country,
was appointed as its sole distributor in
Slovakia. The Rocket Boomer 282
provided for trials in 1998 was the first
two boom hydraulic rig supplied to
a Slovakian mine, and the Rocket
Boomer M2 C was also a first.
Acknowledgements
Atlas Copco is grateful to the management of SMZ for its assistance with the
production of this article.
Kure, Turkey
Access
The vehicle access adit is horizontal,
and connects with the spiral ramp
developed in the footwall of the
orebody down to the sump level. The
orebody, which dips at between 45 and
60 degrees, is accessed from the ramp,
along levels spaced at 12 m vertical
intervals.
The 20 sq m oval-plan spiral ramp
was driven at 5-7 degrees from 932 m
level to 792 m level by hand between
1998 and 2000 using Atlas Copco BBC
16W pneumatic rock drills with jacklegs. This work was carried out under
Mining methods in underground mining
73
Kure, Turkey
Development
An Atlas Copco Rocket Boomer 282
equipped with COP 1838ME rock drills
is used to develop the ore and waste
drifts.
The Rocket Boomer has one extending boom to facilitate drilling off the first
rounds in strike drifts at right angles.
Drill hole diameter is 45 mm,
and hole length 3.5 m. The mine has
conducted trials of bits from different manufacturers, and has settled on
Secoroc as the most cost-effective.
Around 250 m /month of drivage
is required to keep pace with the
stopes, all of which are mined on the
retreat.
Most development is within the competent footwall rock mass. The orebody
exhibits different rock mass characteristics. Ground support is by shotcrete,
bolting with mesh, mesh reinforced
shotcrete, standard Swellex in 2.4 m
and 3.3 m lengths, and cement grouted
bolts in 3 m, 4 m and 6 m lengths.
Two manually-controlled Atlas Copco
Scooptram ST6C loaders are used for
mucking development faces.
Production
The mining method is longhole bench
stoping with post backfill. The ore is
developed by driving strike access drifts
with cross sectional area of 21.68 sqm
74
Kure, Turkey
Surface
Belt conveyor
Flexowell
Ore
Grizzly
Feeder
Belt conveyor
Crusher
Cemented backfill
Development
HW
Production drilling
HW
slot
Filling
HW
HW
75
Kure, Turkey
Rock handling
The 2.5 m-diameter main orepasses are
also longhole drilled using the Rocket
Boomer 282, or hand drilled. An orepass system to the 804 level feeds the
underground crusher. Crushed ore sized
at 10 cm travels along a conveyor belt
to a feeder, and into a Flexowell vertical conveyor belt system at 792 level.
A trunk conveyor at average grade of 8
degrees transfers the ore to the surface
primary crusher.
There are four vertical shafts for
backfilling at Asikoy, with three subvertical shafts.
Two types of fill are used for backfilling. These are cemented rock fill
(CRF) and uncemented waste fill (WF).
CRF, with a cement content of 5% by
weight, is used for backfilling of prim
ary stopes. Secondary stopes are waste
filled. Minetruck MT2000 trucks are
used for both types of backfilling.
SFTA has a ten-year cont ract
to produce 30,000 t/month of ore
grading 2% copper at a fixed price per
tonne, although 414,000 t was produced
over the last year. The ore is concentrated to 17% at site, and is trucked to
the port of Inebolu, some 25 km away,
from where it is shipped to a smelter
76
Training
This is the first mining operation where
SFTA has been involved and, being
the only Turkish-operated mechanized
mine, the company takes education
and training very seriously. Atlas
Copco undertook the training of the
mine instructors, and SFTA has carried on, giving every man on the mine
specific education, each with a course
every three months. The average age of
operators is around 30, and most have
been with the group for many years.
Acknowledgements
Atlas Copco is grateful to the management of Asikoy copper mine for
the opportunity to visit the project.
Particular thanks are due to Kenan
Ozpulat, project manager, and Serkan
Yuksel, chief mine engineer, for their
assistance at site and in reading draft.
Tara, Ireland
Back on track
Tara Mine had been finding it difficult
for many years to meet its targets. Today,
however, productivity is back on track
and Tara has returned to profitability.
Swedish mining company Boliden
took over in January, 2004. Since then,
significant improvements have been
made following the introduction of revised management practices and more
modern equipment.
Boliden is well known for its successful copper operations in northern Sweden, and its zinc deposit at Garpenberg
in the central, south-eastern part of the
country. For many years the company has
co-operated closely with Atlas Copco,
so when the time came to upgrade the
equipment fleet at Tara, Atlas Copco
was the natural choice.
The Tara fleet includes a Cabletec
cable bolting rig, two Rocket Boomer
M2 C drill rigs for development and
three Scaletec rigs for scaling roofs and
walls.
A Simba production drill rig is also
on order. Added to this, Atlas Copco
has provided substantial operator and
maintenance training programmes for
each equipment type.
Meeting targets
Tara Mine is now meeting its target of
close to 200,000 t of zinc concentrates
per year and 40,000 t of lead concentrates.
All workings are underground in an
area of some five square kilometres.
The Tara Mines orebody was discovered in 1969 and production began in 1977 following extensive
exploration work. The mine celebrated its 30th anniversary on June 4, 2007.
Atlas Copco equipment, such as this Rocket Boomer M2 C drill rig, plays a central role, pictured here with
instructor Lars-Olov Jansson (left) and operator Noel Dunphy.
Improved morale
An important aspect of the changes taking place at Tara is the positive effect
on morale. All operations are now characterized by enthusiasm and co-operation
among both miners and management.
The operation is backed up by a programme of technology transfer from
the Garpenberg Mine to Tara. The mine
is very development-intensive, having
to drive at least 13,500 m of drifts per
year. This consists of some 4,000 m for
78
Blasthole markings in stope development at a Tara face, seen from the cab of the
Rocket Boomer M2 C drill rig.
1
2
1
2
1
A
See cross
oss section
secti
Fig 1: Plan of the 1135 level at Tara Mine. 1= primary stopes 2= secondary stopes
A common hole depth can be activated enabling all holes in the drill pattern
to end up in the same vertical plane,
irrespective of the starting point. This
feature prevents overdrilling which saves
drill metres and gives a more efficient use
of the explosives. A built-in program
compensates for any mechanical deflection of the booms.
Depending on the application area,
the rig drills holes up to 5.4 m long.
Drift sections vary from 4.5 m wide x
4.2 m high to 5.5 m wide x 5.5 m high.
The blasthole diameter is 45 mm and 57
holes are normally drilled. In the centre,
there are four relief holes, 102 mm in
diameter. The holes are blasted using
bulk emulsion explosive with Nonel detonators. A round with 4.9 m hole depth
gives a pull of 4.7 m.
Of the two Rocket Boomer M2 C rigs
delivered in 2006, one uses 16 ft (4.88m)
rods and the other uses 18 ft (5.59 m)
rods. A third rig will also use 16 ft rods,
and all rigs are equipped with BUT 32
booms.
Streamlined surveying
The mines survey department carries
out all surveys of drifts in three planes
Mechanized scaling
In keeping with Taras emphasis on safety in all procedures, scaling now takes
place after every blast. The three Atlas
Copco Scaletec scaling rigs are more
compact and easier to operate than their
predecessors.
Scaletec machines equipped with
Atlas Copco SB 300 scaling hammers
are working on a three-shift cycle. In the
development cycle, scaling takes place
immediately after mucking out and before any necessary ground support. The
rigs are integrated into the development
cycle to speed it up, but they also scale
other areas which are not shotcreted,
such as high-stress areas, before they
come into production.
< 18 m
956 Z
15-20 m
Fig 2: Cross section AA showing the blasthole drilling pattern at SWEX and stope-pillar geometry.
70
Fig 3: Long section showing the drilling pattern of the blasthole fans and mucking.
Automatic grouting
The mine is doing away with manual
handling of cement for safety and efficiency. The grout tank is delivered to
the site and loaded up by forklift and the
Cabletec carries enough grout on board
for a whole shift.
The grout mix has to be fluid enough
to be pumped into the hole but rigid
enough to remain in it and hold the
cable whilst curing. There is sufficient
hose on board to pump grout to the
end of a 25 m-hole, which meets all of
Taras needs.
Mining methods in underground mining
stope and curing before the adjacent pillars can be mined. Sufficient compressive strength is achieved after 56 days
with a 15:1 sand/cement ratio. Then, in
order to prevent subsidence, the open
pillar stopes that are not required for
mine support are filled with low cement
ratio, classified tailings.
The introduction of some new methods, along with the purchase of new equipment, has required training for both
safety and efficiency.
Many of Taras operators have also
visited the Atlas Copco facility in rebro where they had the opportunity to
familiarize themselves with the new
units, prior to delivery at the mine. For
example, prior to the delivery of the
Scaletec rigs, Atlas Copco trained six
Scaletec operators for Tara during a fiveday programme, followed by a course
for Tara service technicians.
Acknowledgements
Atlas Copco is grateful to the management at Tara Mine for their assistance
in the production of this article.
From left, Patrick White, Mine Captain, Derek Douglas, Cabletec operator and Benson Plunkett,
Senior Operations Engineer, in front of the Cabletec rig.
82
El Soldado, Chile
History
The El Soldado and Los Bronces copper
mines and the Chagres smelter, all located in Chile, are operated by Compaa
Minera Disputada de las Condes.
In addition to its record as a successful mining company, Disputada's operations achieved recognition in 1999
when it became the first industrial
company to receive Chiles National
Environment Award, recognizing its
leadership in environmental practices
and its high standards in environmental
management.
Disputada produces around 250,000 t/
year of copper. When, in 2002, Anglo
American plc agreed to purchase Disputada from Exxon Mobil, it substantially enhanced the quality of its base
metals portfolio, in addition to offering
significant synergies with its other
Chilean copper operations, the Doa
71
71
70
70
EL
ELSOLDADO
SOLDADO
SOUTH
SOUTH
AMERICA
SOUTH AMERICA
AMERICA
SOUTH
AMERICA
CHAGRES
CHAGRES
QUILLOTA
QUILLOTA
VALPARAISO
VALPARAISO
LOS
LOSANDES
ANDES
LOS
LOS BRONCES
BRONCES
CCH
HILI
ELE
SAN
SANANTONIO
ANTONIO
SANTIAGO
SANTIAGO
EL
ELTENIENTE
TENIENTE
RANCAGUA
RANCAGUA
AR
RG
GE
EN
N TTIIN
A
NAA
33
33
34
34
El
deposites
El Soldado's
Soldado's
deposites
El
Soldado
deposits
83
El Soldado, Chile
Development
Boomer drilling
5" Simba
DTH drilling
DTH Drilling
Raise
Simba
drilling
2"Simba
radial drilling
Ore-pass
Extraction level
Transport level
Scooptram
loading
Problematical geology
The El Soldado deposit is located in the
Lower Cretaceous Lo Prado formation,
and is thought to be of epigenetic origin.
The main host rocks are trachytes, followed in importance by andesites and
tuffs. Copper mineralization occurs as
84
El Soldado, Chile
Mine stability
Underground layout
Mine stability is a matter of prime importance in the planning process, particularly as the El Morro open pit is situated
10.0 m
17
40-50o
2
to
Ventilation
shaft
18.0 to 20.0 m
150.0 m
2m
Max 15.0 m
to
22
Max 15.0 m
40-50
Shaft
2.5 x 2.5 m
17
50.0 m
10.0 m
Max 15.0 m
Max 15.0 m
17
Ventilation
shaft
10.0 m
to
+ + +
++ + +
++ + + +
22
17
40-50
to
22
+
++
++
40-50o
18.0 to 20.0 m
18.0 to 20.0 m
18.0 to 20.0 m
OP
OP
Shaft
E
Max 15.0 m
= 1.5 m
Ventilation
shaft
Shaft
2.5 x 2.5 m
150.0 m
Max. transport distance
Shaft
85
El Soldado, Chile
Production stopes
adp 450
50 to 75 m
50 to 75 m
Nonel
B
A
45
45
86
El Soldado, Chile
Equipment maintenance
El Soldado has been through a phase
of equipment replacement. Two of the
Outlook
El Soldado's main objective is to continue with its tradition of excellence in
safety and cost competitiveness. The
underground mine production is being
reduced as open pit output increases,
and variants of the exploitation method
will be introduced to recover minor
volume reserves using automated radial
drilling to over 40 m depth.
El Soldado's mining plan is intrinsically linked to its geotechnical and geometric conditions, and so improvements
to the monitoring and data-collection
systems, in order to obtain more precise
geotechnical engineering, are constantly
being studied.
Acknowledgements
This article is based on interviews with
Nelson Torres, Mine Superintendent at
El Soldado, and extracts from the following paper: Contador N and Glavic
M, Sublevel Open Stoping at El Soldado
Mine: A Geomechanical Challenge.
87
El Teniente, Chile
El Teniente
El Teniente is the worlds largest underground mine, with over 2,400 km of
development to date. The mine is located at 2,200 m asl, some 80 km south of
the capital city of Santiago. The total
History
According to legend, El Teniente was
discovered by a fugitive Spanish official
Mining methods in underground mining
El Teniente, Chile
formed around a central, barren, breccia pipe of 1.0 to 1.2 km diameter, surrounded by a mineralized rock mass.
The bulk of the mineralization within
the orebody is typical of massive, homogeneous copper porphyries. In fact, El
Teniente is one of the largest porphyry
deposits of copper in the world. The main
rock types of the deposit are: andesite
73%, diorite 12%, dacite 9% and breccia
6%. At some time during its history,
the deposit was affected by supergene
alteration through percolation of meteorological water close to surface, which
gave rise to secondary mineralization.
This secondary ore is high in copper
grade, but weak, and of good fragmentation and caveability. In contrast, the
deeper primary mineralization is relatively low in copper grade, harder, and
of moderate fragmentation and caveability. As can be appreciated, secondary
ore and primary ore require very different approaches in terms of mining.
Reserves
In total, the El Teniente orebody measures 2.8 km-long, 1.9 km-wide, and 1.8
km-deep. Schematically, the deposit is
Mining method
El Teniente, Chile
Esmeralda pre-undercut
Exploitation sequence
The panel caving exploitation sequence
initially used involved development
and construction of production levels,
undercutting at the undercut level, and
ore extraction. However, the dynamic
caving fronts, under high stress conditions of 40-60 Mpa, resulted in substantial damage to the infrastructure.
Indeed, extraction in El Teniente Sub
6 Sector had to be stopped in March,
1992 after several rockbursts caused
fatal accidents, reflecting the low level
of knowledge at the time about mining
in primary rock. Between June, 1994 and
90
El Teniente, Chile
the undercut level difficult. The effective extraction rate defined for the Esmeralda sector was 0.14 to 0.44 t/day/
sq m at the initial caving stage, and
reached 0.28 to 0.65 t/day/sq m at the
steady-state caving stage. The height
of primary ore column to be exploited
is around 150 m, relatively low if compared with Teniente 4 Sur, where the
height is over 240 m.
At Esmeralda, 7 cu yd LHDs working on the production level load and tip
into 3.5 m-diameter ore passes. Here,
teleremote controlled hydraulic breakers positioned above 1 m x 1 m grizzlies
break any oversize rock before it goes
through the ore pass and into the loading bin. On the haulage level, the
mineral is loaded into trains featuring
Automatic Train Protection (ATP) and
consisting of a locomotive with eight 50
t cars. These trains, which were retrofitted with an Automatic Train Operation
(ATO) system, tip into storage bins
which feed a 5.0 m-diameter orepass
to the main transport level Teniente 8.
Trains with 90 t electric locomotives
and 18 cars each of 80 t capacity carry
the mineral out to the Coln concentrator. The main haulage level at Teniente
8 was recently upgraded, incorporating
new technology similar to Esmeralda.
Basic concepts
In the conventional panel caving and the
pre-undercut variant, the same basic concepts apply. The main difference is the
sequence of each of the operational elements. In the conventional panel caving
method, the sequence of activities is:
development of tunnels on each level
for production and undercut; drawbell
opening; undercut blasting; and extraction. In the pre-undercut variant, the undercut is excavated first, and the production level is developed subsequently
within the stress-relieved zone: development of the undercut level; undercut
blasting; development of the production
level; drawbell opening; and extraction.
The main challenge associated with
this variant involved the undercutting.
Several alternatives were tried, with
the current preference being a flat, low
height 3.6 m undercut. The undercut is
blasted some 80 m ahead of the actual
production zone, with the production
level and drawbell development following around 22.5 m behind the undercut,
and 57.5 m ahead of the production
zone.
The undercut comprises drives, 3.6
m-wide by 3.6 m-high, developed parallel to each other on 15 m centres. The
excavation of the undercut is achieved by
blasting three- or four-hole fans, some
7 m to 10 m length, drilled into the sidewall. The drill holes are fanned slightly,
to ensure an undercut height equal to
the height of the drives. Swell material
from each undercut blast is removed by
LHD to provide a free face for the next
blast. The production haulage level is
HW
FW
HW
HW
FW
FW
HW
FW
91
El Teniente, Chile
Undercut area
Production
area
22,5
m
The
57,5 m
Undercut area
Production
area
Preparation area
80 m
22,5 m
57,5 m
4
5
2
4
5
3
1
1. Development
2. Drilling & blasting to start caving
3. Development
4. Open trenches (boxholes + drilling)
5. Extraction
1. Development
2. Drilling
& blasting
to start caving
Principle
of pre-undercut
at Esmeralda.
3. Development
4. Open trenches (boxholes + drilling)
5. Extraction
Preparation area
80 m
Production at Esmeralda
Cave undercutting at Esmeralda is presently carried out with the 'parallel long
hole' technique, which basically consists
of excavating an 855 cu m pillar of solid
rock 11.4 m-wide, 25 m-long and 3
m-high. A triangular pattern of 14 parallel long holes of 3 in-diameter, with 9
rows of 2 holes and 1 hole each is used.
This pattern has better efficiency,
absorbs blast hole deviation, and avoids
formation of residual pillars.
Drilling is carried out with an Atlas
Copco Simba H157 drill rig, whose output is 60 m/shift of 3 in-diameter holes
and 85 m/shift of 2.5 in-diameter holes.
Standard ANFO is the column charge,
with 300 gm cylindrical pentolite as the
booster, detonated using Nonel.
Atlas Copco equipment at Esmeralda
includes one Rocket Boomer, two Boltec
rigs, two Simba rigs and one 3.5 cu yd
Scooptram loader.
In the production level, a f leet of
nine LHDs is used, including Atlas
Copco Scooptram ST6C and ST1000
loaders of capacities 6 cu yd and 7.3 cu
yd respectively.
Raiseboring
In an interesting application during the
development of Esmeralda, two Atlas
Copco Robbins raiseboring machines,
a 34RH and a 53RH were used. These
are multipurpose machines, and can be
employed for upwards boxhole boring
or down reaming, as well as conventional raiseboring.
At Esmeralda, the Robbins 34RH unit
was used in the production level to drill
draw bell slot vertical holes approximately 15 m to 20 m-long and 0.7 mdiameter. The machine worked three
shifts/day, giving a penetration rate of
2.1 m/h. It had a capacity of 93 m/month
and a utilization rate of 39%.
The Robbins 53RH was employed to
bore 1.5 m-diameter boxholes up to 75
m-long for use as ventilation shafts, and
inclined pilot raises for orepasses, with
an average length of 24 m. The machine
worked three shifts/day, giving a penetration rate of 1.8 m/hr. It had a capacity of 111 m/month and a utilization
rate of 57.3%.
Atlas Copco trained the operators
from El Teniente, and was in charge of
the equipment maintenance during the
first few months.
El Teniente, Chile
Maintenance programme
Today, in terms of maintenance, El Teniente is close to being self-sufficient, and
does most of its own work. Maintenance
programmes for all the units are based
on the suppliers' information, plus experience gained in use. All this data is
held on a centralized system that monitors all machines, checks when they need
maintenance, and organizes what spares
will be required. There are centralized
maintenance workshops for drill rigs,
LHDs and utility vehicles, with one
major workshop for each machine type.
In this way, the maintenance department
and its team provide a central technical
and maintenance service to all the
sectors within El Teniente. Smaller
workshops dispersed throughout the
complex are used for repair or maintenance jobs of less than four hours
duration.
Major rebuilds and repairs are handled at the central workshops on surface, one for component rebuilds, and
the other for major machine overhauls.
Atlas Copco maintains a team of
technicians permanently at the mine,
working with the maintenance department on the commissioning of new
equipment, and providing support and
operator training during the warranty
period of the units.
Recent developments
Framed within Codelco's current US$4.2
billion strategic plan, the US$1.1 billion
Plan de Desarrollo Teniente (PDT) is the
great mining, technical and management
strategic plan of El Teniente Division
for the next 25 years. Its objective is to
expand the production capacity at all
levels, including mine, concentrator,
smelter, hydrometallurgy and services,
and increase El Teniente's economic
value by over 90% from US$2 billion to
US$3.8 billion.
Amongst other things, the plan contemplates the incorporation of worldclass technology.
Occupying an area of 190,000 sq m,
Reservas Norte/Sector Andesita is located north of the Teniente Sub-6
sector. Its reserves are estimated to be
125 million t, with an average grade
of 1.14% copper. Its useful life will
last until 2019, and during operation it
will require a workforce of 280 people.
Construction was started in 2000 for
production commencement in 2003.
Production is planned to reach 35,000 t/
day and, like Esmeralda, Reservas Norte
is being exploited by panel caving with
the pre-undercut variant. Main equipment includes 14 LHDs of 7 cu yd capacity, 16 plate feeders, eight 80t trucks,
four hydraulic breakers, and five 1,400
HP fans. On the production level, the
LHDs tip into 34 m-long orepasses.
On the haulage level, the 80t trucks,
loaded by plate feeders, empty the min-
El Teniente, Chile
References
94
State owned Codelco is Chiles largest company and the worlds largest producer of refined copper.
The Codelco-owned El Teniente
(The Lieutenant) mine is presently
the worlds largest underground
mining operation. The mine average production rate is currently
126,000 t/day. Boxhole boring between the production and haulage
levels using Atlas Copco Robbins
machines is a major component in
achieving such high outputs.
Recently, two raise borers modified to suit the El Teniente mine
conditions were commissioned by
Atlas Copco. They were evaluated
for three months, during which
time the crews were trained in
their operation. Both exceeded the
set target performance criteria.
Slot hole
0.7 m diam/15 m long
Loading, LHD
Dumping
Orepasses
Ventilation
shaft,
1.5 m diameter
35 m long
Introduction
Codelco, renowned for its refined copper
output, is also the second ranked world
supplier of molybdenum, as well as being
a major producer of silver and sulphuric
acid, both of which are by-products of its
core copper production.
The El Teniente mine, located high
in the Andes at an elevation of 2,100 m,
has been producing copper since 1904.
The orebody is 2.8 k m-long by
1.9 km-wide, and is 1.8 km-deep, with
proven reserves of some 4,000 million t,
sufficient for a mine life of 100 years.
Approximately 2,800 miners work
seven levels on a 24 h/day, 7 day/ week
operation.
El Teniente production increased significantly in 2005, when its new Esmeralda section came on line, using the
pre-undercut panel caving method. Overall mine output has increased by 31,000
t/day, with 45,000 t/day coming from
the Esmeralda Project, making it the
most important sector in the mine. The
two new boxhole boring systems supplied by Atlas Copco Robbins are a
vital part of this production system.
Production level
Robbins
34RH
Robbins
53RH
Tapping
Ventilation
shaft, 1.5 m
diameter
45 m long
(max: 75 m)
Transportation level
Ventilation level
95
Boxhole equipment.
Mine requirements
El Teniente tendered for the purchase of
two boxhole boring units to excavate
the draw bell slot holes for the panel caving operation. These units would also
be used to bore ventilation raises and
ore passes between the production and
the haulage level. The vertical draw bell
slots are generally 15 m-long and 692
mm-diameter. A total of 800 m, comprising 45-50 shafts, are bored annually.
Because drifts have not been developed on the production level, all ventilation raises and ore passes are bored
from the haulage level and upwards
using the boxhole boring technique. The
average length of the vertical and inclined ventilation raises is 25-50 m. The
inclined ore passes average 25 m-long,
but this varies up to 75 m-long. The total
annual requirement for 1.5 m-diameter
bored raises is 1,000 m.
Restrictions are placed on the machine design by the size of the underground sections. Work sites measure
3.6 x 3.6 m, and maximum transportation dimensions are 2.5 m-wide x 2.5
m-high x 4.8 m-long. The machines must
either be self-propelled or transported
on rail, and have to have tramming and
directional lights, as well as a fire extinguisher system. The mine electrical installations provide power at 575-4,000
96
V, 3-phases at 50 Hz, and 24-220 V, single phase at 50 Hz. Each machine is designed for three, or less, operators per
shift.
The operating environment is 2,300 m
above sea level, with teperatures from
+25 degrees C to 0 degrees C. Relative
humidity varies from 15% to 90% in
the mine, where acid water and occasional blast vibrations may be experienced. Both machines are operated 24
h/day, 7 days/week, with a maximum
machine utilization of 15-16 h/day.
Evaluation period
An evaluation period of three months
was established to study the performance
capabilities of each machine. Target performance criteria for the smaller slot
hole machine was set at 264 m bored
during the three month period, and 330
m for the larger boxhole machine.
This performance target was based
on a 24 h/day operation, with net available operating time of 15-16 h. The
number of operating personnel required,
set-up and moving time, the rate of penetration and machine availability were
all recorded during evaluation period.
Atlas Copco boxhole boring units
Robbins 34RH and 53RH were found
to meet the requirements of the up-hole
boring tender, and were selected by the
mine. Built on the experience of the
During pilot hole drilling and reaming, the rubber sealed muck collector
is applied adjacent to the rock face. The
muck slides on a chute assembly to the
rear of the machine.
The two earlier Robbins 34RH machines featured a 270 degree working
range, with muck spilling to either side
or to the rear end of the machine, whereas
the muck chute on the new El Teniente
34RH machine has a working range of
90 degrees, due to simpler and more
compact design.
The Robbins 34RH features a remote
controlled hydraulically operated slideopening worktable for use in both downreaming and boxhole boring applications. The entire drill string, including
boxhole stabilizers and reamer, can pass
through the worktable of the machine.
The standard frame Robbins 34RH
currently in use at El Teniente accommodates a 692 mm-diameter reamer
through the worktable, while a wide
frame model of the 34RH accommodates a 1,060 mm-diameter reamer.
The Robbins 34RH worktable is
equipped with semi-mechanized wrenching, which features a hydraulically
powered forkshaped wrench manipulated from the operators control
console.
The rod handler is designed to pick
up all drill string components, including boxhole stabilizers and reamer.
Robbins 53RH
The Robbins 53RH is a low profile,
medium-diameter raise drill, suitable
for boring orepasses and ventilation
shafts. It is a versatile multi-purpose
machine, capable of boring upwards
boxhole, downreaming, or conventional raiseboring, without modification
to the drive assembly.
It has a hydraulic drive to enable
variable rotation speeds and has dual
drive motors placed offline on a gathering gearbox that transmits torque to the
drive heads.
The Robbins 53RH features a raiseboring and a boxhole float box, which
allows the boring methods to be changed by simply installing drill rods in
either the upper or lower float box. In
addition, this multi-purpose unit is provided with a removable water swivel, to
facilitate pilot bit flushing in both raiseboring and boxhole boring modes.
The El Teniente machine has been
substantially upgraded from previous
versions of the Robbins 53RH, to increase its productivity and working
range. The input power has been increased by 31% to 225 kW, the torque has
been increased by 44% to 156 kNm,
and the thrust by 21% to 3,350 kN.
To achieve the same low profile as
standard Robbins 53RH machines, high
thrust telescopic cylinders have been
used. This has resulted in a machine
with an overall height of just 2.9 m that
utilizes 750 mm-long drill rods with an
outer diameter of 286 mm.
For ease of operation, the unit is
equipped with semi-mechanized wrenching in the worktable, as well as the
headframe. This features a hydraulically powered forkshaped wrench manipulated from the operators control
console.
The larger Robbins 53RH does not
feature an opening worktable, as the
wings of the stabilizers and the reamer
are attached on top of the machine.
Muck is handled by a separate collector system designed to suit the machine. Unlike the Robbins 34RH, this
muck collector is not integrated into
the machine design, but is attached to
the rock face by means of rock bolts.
As it is separated from the derrick
Diesel powered crawlers are used for transporting Robbins 34RH and Robbins 53RH.
Additional equipment
The boxhole boring machines working
in El Teniente were each delivered with
a diesel powered crawler, for rapid
movement of the derrick from site to
site. The newly designed crawler features a cordless remote controlled operating system and a high-power Deutz
diesel engine for high-altitude operation
and minimal environmental impact.
To give the mine better control over
machine productivity, a Data Acquisition System was delivered with each
machine. This records operating variables in real time, and stores them on
a memory card. It also features a display panel that shows the parameters
being recorded. The machine operator
can view any variable, as well as current
time and date, and battery life during
operation.
The recording brick is configured to
log data to the memory card every 30
seconds. During the interval, variables
are continuously monitored and key
points are logged. The Data Acquisition
System is provided with a data analysis
software package which processes the
output from the recording brick stored
on the memory card, and creates graphical plots of the data. The software
also generates data files that can be
inserted into spreadsheets.
98
Conclusion
The application environment in the
El Teniente mine placed high demands
on the boxhole boring equipment supplier, both in size constraints, and in
operation of the equipment. The mine
personnel also had aggressive performance expectations, in keeping with
the established high productivity of the
mine.
Atlas Copco chose to offer its proven
34RH and 53RH boxhole machines with
customized features to meet the special
needs of El Teniente. Most of these
Robbins 34RH.
Acknowledgement
Atlas Copco is grateful to the management and staff at El Teniente for their
help and assistance with this article.
Rock Type
Composition Density
[%]
[ton/m3]
Andesite Fw
36
2.75
Andesite Hw
24
2.75
Anhydrite Breccha
20
2.70
Andesite Breccha
12
2.70
Diorite 8
2.75
UCS Youngs
[MPa] Modulus
[MPa]
[---]
100
55
125
55
115
55
100
50
140
60
Poissons
Ratio
0.12
0.17
0.17
0.12
0.15
100
Antofagasta, Chile
Large operation
The Sierra Miranda Mine, located about
60 km northeast of the city of Antofagasta, is one of Chiles largest underground mining operations and has a history of using the most modern mining
techniques and equipment available.
Sierra Miranda lacks a substantial
power facility, with the exception of
electricity for lighting and ventilation,
and has no water or air supply lines.
As a result, to mechanize effectively,
all of its underground equipment has
to be self-sufficient. The drill rigs, for
example, are all diesel-hydraulic with
independent water-mist flushing systems.
The mines total production is 3.3
million t/y, 1.1 million t of which is
waste rock from development work, and
the remaining 2.2 million t is copper
ore with an average grade of 0.75%.
The host rock is volcanic andesite
and the mineral deposit is principally
copper malachite, a combination of
Efficient production
Sierra Miranda has a workforce of about
300, including contractors personnel.
The mining method is sublevel stoping, without backfill. As the orebody is
relatively narrow at 4-10 m-wide it is
necessary to use an extraction method
that is both precise and focused.
The deposit is situated near the
surface, which from a geo-mechanical
point of view is favourable, as the support pillars in the mine are not subjected
to excessive pressure.
Until recently, Atlas Copco ROC 460
truck-mounted drill rigs with short
feeds and DTH hammers were used
101
Antofagasta, Chile
Schematic of sublevel stoping in a narrow vein using the Simba M6 C to drill down holes.
102
Acknowledgements
Atlas Copco is grateful to the owner
and management at Sierra Miranda
mine for their assistance with the preparation of this article which first
appeared in Mining & Construction
1-2007.
Geology
The mineral deposits zone at the central
Mount Isa mining complex lie in an approximate North-South orientation, and
dip towards the West.
Economic copper sulphide mineralization lies within a brecciated siliceous and dolomitic rock mass, known
locally as silica-dolomite, which is
broadly concordant with the surrounding Urquhart Shale. There are several
copper orebodies. The silica-dolomite
mass which hosts the 1100 and 1900
orebodies has a strike length in excess
of 2.5 km, a maximum width of 530 m,
and a height of more than 400 m. The
recently developed 3000 and 3500 orebodies lie as deep as 1,800 m. Copper
mineralization is truncated by a basement fault, bringing altered basic volcanic rocks (Greenstone) into contact with
the Mount Isa Group sediments. The
dominant sulphide minerals are chalcopyrite, pyrite and pyrrhotite forming
103
COPPER MINE
4/L
5/L
6/L
7/L
&
Black Rock
&
Black Star
Orebodies
LEAD
Racecource
2 kms
Orebody
9/L
10/L
11/L
12/L
13/L
14/L
15/L
Orebodies
13C
MINE
16/L
1100
H75 Shaft
ISA
Star
Black
400 Orebody
M73 Shaft
Black StarOpenCut
Open Cut
Rio Grande
Orebodies
H70 Shaft
R67 Shaft
M64 Shaft
Y59 Shaft
Black Rock
R60 Shaft
M61 Shaft
P61
R62 Shaft
U62 Shaft
P63 Shaft
I54 Shaft
Storage Pit
N52 Fill Pass
Storage Pit
S50 Fill Pass
U51 Shaft
U47 Shaft
M48 Shaft
W44 Shaft
L44 Shaft
X41 Shaft
Shaft
M37 Shaft
4 kms
1900 Orebody
17/L
18/L
19/L
20/L
21/L
3000
&
3500
ENTERPRISE MINE
Orebodies
Copper Orebodies
Zinc, Lead, Silver Orebodies
LONGITUDINAL SECTION
Z
N
orebodies have been established by exploration drilling from the surface and
underground. Despite the depth of the
mines, stresses in the ground are not
as great as at some shallower mines in
other regions of Australia.
Simba H4353 long hole drill rig with COP 4050 rock drill.
104
5500N
5000N
4500N
1500E
Advance south
2
Egg crater pattern
S4
8F
au
lt
Primary Stope
Secondary Stope
Tertiary Stope
Mining methods
The zinc-lead-silver orebodies and
copper orebodies are mined separately,
using slightly different methods, although all operations use forms of open
stoping. In open stoping, blocks of ore
that make up part of the orebody are removed one at a time, with the ultimate
goal of removing all of them.
In the Mount Isa copper mine orebodies, sublevel open stoping, coupled
with secondary and tertiary stoping is
used to extract the ore. Blocks of ore
40 m-wide, 40 m-long at full orebody
height are removed. To do this, 5.0 m x
5.0 m drilling sublevels are developed
at 40 m intervals. At the bottom of
the stope, a number of drawpoints are
mined and equipped to extract the ore.
Blast hole drilling is carried out using
a variety of Atlas Copco Simba rigs, including models H4353, H1354, 366, 269
and 254. On the extraction level, upholes
in a V shape are used to shape the
trough. On the drilling sublevel, the
Simba rigs are used to drill holes in a
radiating fan shape. A slice of ore the
height of the stope is extracted first,
exposing an open area along one side of
the stope, into which progressive blasting is carried out.
The fleet of Simba rigs covers a wide
range of hole lengths, diameters and
orientation possibilities for flexible orebody exploitation capabilities. Holes can
be drilled accurately, with stringent tolerances, for optimum fragmentation of
the ore, and minimal underbreak. Tophammer or ITH (in-the-hole) hammer
105
Cutoff slot
Drilling pattern
Cutoff raise
Drilling sublevel
Zinc-lead-silver extraction
Broken ore
Drawpoint
16B
16B
17D
18E
18E
18B
19C
19A
19C
19/L
19/L
cost-efficient products for MIM operations, resulting in fewer bits for the
same tonnages. MIM and Secoroc are
now really pushing the idea of reusing
material and focusing on wastage. Bit
resharpening, rod straightening and
rod clearing have been introduced with
the resharpening ratio for development
bits now averaging 1.5 times.
Consumable care is an area where
the jumbo operators can improve the
life of consumables and cost per metre,
and Secoroc is required to take a lead
in education in the use of its products.
The companies are working towards
agreeing on and setting expectations
about scaling standards, and procedures to reduce damage.
The initial supply and service contract ran for one year and has since
been extended for three years on a performance-based rolling contract, with
three monthly performance reviews.
107
Ore processing
Lead-zinc-silver ore from Mount Isa
and George Fischer mines is ground to
a fine powder at the Mount Isa facility,
after which a flotation process is used
to separate waste, and produce leadrich and zinc-rich concentrates.
Lead concentrate from Mount Isa
contains 50-60% lead, and around 1
kg of silver/t. After smelting to remove
further impurities, blocks of material,
each containing approximately 3,984 kg
of lead and 10 kg of silver, are transported by rail to Townsville for shipment to MIMs lead/silver refinery
in England. In 2001-2002, lead-zinc
concentrator throughput and recovery
increased, and there was improved
plant reliability at the lead smelter.
Around 51% zinc concentrate is also
railed to Townsville for refining, or shipment to overseas customers. MIM currently produces approximately 190,000
t of lead bullion and 500,000 t of zinc
concentrate each year.
At the Mount Isa processing facility,
there is a chimneystack at the copper
smelter, built in 1955, which is 155 mhigh, and at the lead smelter the stack,
Expansion plans
In the year ending June, 2002, record
copper smelter production of 233,000 t
of anode was achieved. This was up
from 207,000 t for the previous year.
A recent copper study to improve
reserves and efficiencies has resulted in
an increase in reserves to 12 years. This
has led to a planned 40% expansion in
copper production by 2006. A rate of
400,000 t/y for up to 20 years from
Mount Isa and MIMs Ernest Henry
Mine is predicted by MIM.
MIM is planning to expand copper
production by developing the 1900 orebody, the Enterprise Mine 3000 and
3500 orebodies, and the surface open
pit mines in and around existing orebodies. The aim for 2003 was to increase
Mount Isa copper production to 245,000t,
improve the recovery rate in the concentrator following an upgrade, and
increase plant utilization by improving
maintenance practices. It is estimated
Tonnage (million t)
100
200
400
200
108
Acknowledgements
Atlas Copco is grateful to the management of Mount Isa Mines, and in
particular to Jim Simpson, General
Manager Mining, Lead Zinc, for writing
this article which first appeared in
Underground Mining Methods, First
Edition.
melbourne, australia
Long history
Stawell Gold Mine, located about 250 km
west of Melbourne, was first mined in
1853. It was closed in 1926, and stayed
dormant for more than 50 years. It then
re-opened in 1982, and has been in operation ever since.
From 1992 until 2005, Stawell was
owned by MPI Mines, who instituted a
plan to increase gold production from
100,000 oz/yr to 130,000 oz/yr by end2006.
However, the mine recently changed
hands, and is now operated by Leviathan
Resources, who have adopted the same
objective. To meet these targets, bench
stoping with cemented rock fill pillars
in primary stopes is used. With this
mining method, approximately 80%
of the ore is recovered from the stopes.
Remote-controlled loaders shift the ore
out of the stopes, from where four Atlas
Copco MT5010 trucks are employed
hauling it to the surface along a gravel
roadbed maintained by two graders in
continuous operation. A Minetruck
MT6020 was recently added to the fleet.
Stawell management is convinced
that their MT5010 and MT6020 trucks
are the best on the market in terms of
load capacity and performance.
Visual inspection of a Minetruck MT5010 with full load near Stawell portal.
Faster is better
Stawell is a very deep mine with incline access. Inevitably, the adit is the
bottleneck in the production operation,
because it limits the size of truck that
can be employed hauling ore to surface.
However, within the normal underground speed constraints, the faster the
trucks, and the cleaner they run, the
greater will be the amount of ore that
gets to surface.
At Stawell, getting the ore to surface
involves an 8-9 km drive, which, even
with Minetrucks, involves a round trip
of 100 minutes. On the 1:8 gradient,
speed under full load is 12 km/h, some
melbourne, australia
SCALE
500m
RESERVE BLOCKS
INDICATED RESOURCE BLOCKS
INFERRED RESOURCE AREA
MINED AREA
GOLDEN GIFT DOMAINS
EXPLORATIONS TARGET
BASALT
PORPHYRY
FAULT BLANK
500m
1000m
1500m
Getting the ore out at Stawell involves an incline of 1:8 to the 400 m level and then 1:10 to surface.
Minetruck MT5010
The Atlas Copco Minetruck MT5010
truck is currently offered with the
One of the four MT5010 mine trucks at Stawell Mine with manager Bill Colvin and driver Bruce Mclean.
110
melbourne, australia
The Minetruck MT5010 exits from the Stawell portal after a 9 km uphill drive.
Minetruck MT6020
The Atlas Copco Minetruck MT6020
is a fast all-wheel drive 60 metric ton
capacity articulated underground truck,
with an ergonomically designed forward
seating enclosed operators compartment for unparalleled productivity in
demanding mines. The cabin is ROPS
and FOPS certified for maximum safety
and minimal operator fatigue. It is air
conditioned, and has a tilt-telescopic
steering wheel, back up camera monitor, and trainer seat. The vehicle features
an optimum box profile for clean and
fast dumping, and its front axle suspension has a gas-hydraulic system to
melbourne, australia
Minetruck MT6020 during the field test at Stawell Gold Mine in Australia.
Continuous support
The routine performed by the mines
maintenance team includes checking
main functions after each 12-hour shift,
as well as more thorough services at
125 hours, and the recommended intervals at 250 hours.
The Minetrucks, despite their arduous working situation, are acknowledged by Stawell management as being
the best performing trucks on site, with
the highest t/km and excellent availability. As a result, they now constitute
70% of the hauling fleet.
Where problems have been experienced, the mine knows it can rely on
support from Atlas Copco. If they need
a part, or a question answered, Atlas
112
Acknowledgements
Atlas Copco is grateful to the management and staff at Stawell mine for
their assistance in the production of
this article.
Loaded Minetruck MT6020 during the field test at Stawell Gold Mine in Australia.
Geology
The Olympic Dam mineral deposit
consists of a large body of fractured,
brecciated and hydrothermally altered
granite, a variety of hematite-bearing
breccias and minor tuffs and sediments.
The breccia lies under 300-350 m of
barren flat-lying sediments comprising
limestone overlying quartzite, sandstone
and shale. The deposit contains semidiscrete concentrations of iron, copper,
uranium, gold, silver, barium, fluorine
and rare earth elements. These are scattered throughout an area 7 km-long and
4 km-wide, and having a depth of over
1,000 m. There are two main types of
mineralization: a copper-uranium ore
with minor gold and silver within numerous ore zones, making up most of
the resource; and a gold ore type which
occurs in a very restricted locality.
There is distinct zonation evident
throughout the deposit, ranging from
iron sulphide (pyrite) at depth and
Northern
Teritory
Queensland
Western
Australia
Perth
Brisbane
New South
Wales
Victoria
Melbourne
Tasmania
Sydney
Canberra
South Australia
Lake Eyre
North
Coober
Pedy
Lake Eyre
South
Hobart
a
OLYMPIC DAM
Wo
ome
r
Darwin
Lake
Torrens
Port
Augusta
Adelaide
Mine programme
The Olympic Dam mine comprises underground workings, a minerals processing
Mining method
A carefully sequenced and monitored
method of sublevel open stoping is employed to extract the ore. This was chosen
chiefly on the basis of: the depth of the
orebody and volume of overburden; the
large lateral extent of the orebody; the
geotechnical attributes of the ore (see
above), the host rock and barren materials,
Resource ranking
Production ranking
% of world production
Copper
No.5
No.17
1.4%
Uranium
No.1
No.2
11%
114
Activity Overview
Mucking Overview
STOPE
DRAWPOINT
STOPE
MUCKING
on
cti
tra ive
x
E Dr
DUMPING
IV
UNDERCUT
TI
AC
R
XT
DRAWPOINT
ON
DR
E
LOADER
TRAMMING
Dumping Overview
MOBILE ROCK
BREAKER
Tramming Overview
STOPE
TRUCK
HAULING
TO ORE PASS
IV
DR
ION
T
AC
TR
EX
N
TIO
AC
TR
X
E
IV
DR
LOADER TRAMMING
TO ORE PASS GRIZZLY
FINGER PASS
GRIZZLY
ORE PASS
GRIZZLY
ON
CTI
RA E
T
X
V
I
E DR
E
LOADER
TRAMMING TO
ORE PASS <250 M AWAY
TRUCK DUMPING
INTO FINGER PASS
GRIZZLY
ORE PASS
TO TRAIN LEVEL
Activity overview showing mucking, tramming and dumping of ore from a typical stope.
ROCK fill
CAF fill
ROCK fill
ROCK fill
Unmined
Unmined
Unmined
CAF fill
Unmined
Unmined
Unmined
Unmined
Designed stopes
Unmined
Unmined
Unmined
CAF fill
Primary
Secondary
Tertiary
Primary
Secondary
CAF fill
FINGER PASS
GRIZZLY
400 m B.S.L.
450 m B.S.L.
Loaders and Trucks dump ore
into the Ore Pass Grizzly's.
ORE PASS
The Grizzly is essentially a large
steel grate designed to stop
large rocks getting into the ore pass.
These large rocks are broken up
520 m B.S.L.
by a Mobile Rock Crusher.
Ore slides down the ore passes
into the Surge Bin.
550 m B.S.L.
SURGE BIN
FINGER PASS
570 m B.S.L.
650 m B.S.L.
The Ore is loaded onto the Train.
The Train continues to the Crusher,
dumps the ore which is crushed
and hauled to the surface
36 tonnes at a time.
116
FINGER PASS
TRAIN LEVEL
First the slot is formed around the raisebored hole, and then subsequent blasts
peel away the ore into the void. Sufficient broken ore has to be removed by
loader from the bottom sublevel of the
stope at the footwall to allow for swelling of the rock and the next firing
stage.
The extraction process continues in
this way, and then all broken ore is removed leaving a roughly rectangular
prism-like vertical void, which is then
backfilled. The broken ore is transferred
to one of the permanent, near vertical,
orepasses linking the extraction levels
with the rail transport level. These load
minecar trains, which carry the ore to
the underground crusher and shaft hoist
system.
The optimum geotechnical dimensions of the unsupported open stope are
usually insufficient for complete extraction of the suitable ore at that position,
so a series of secondary, and maybe
tertiary, stopes have to be developed
adjacent to the primary stope. This necessitates a substantial structural fill for
the primary stope, to ensure the structural security of the adjacent stopes
without leaving a pillar. This comprises
Mining methods in underground mining
Simba 4356S longhole drill rig with COP 4050 tophammer rock drill.
Amount
1,100 m/month
24
300,000 tonne
30,000 tonne/month
Ten months
One month
Three months
178,523 tonne
2,890 tonne
64,289 oz
643,975 oz
117
Intake Raise
Exhaust Raise
Slot Raise
Internal
Exhaust Raise
Ore Pass
Intake air
Exhaust air
Mine planning
Extensive site investigation, analysis of
rock properties, and computerized planning and control procedures aid mine
management in the most efficient exploitation of reserves. The programmes
are discussed at meetings with relevant
line managers to be agreed or modified,
before implementation.
As geotechnical conditions are so important for stope stability, the materials
properties of the intact rock have been
determined from more than 200 laboratory tests. A three-dimensional model
of estimated Uniaxial Compressive
Strength (UCS) has been developed
for the resource area. Evaluation of
drill core logs indicates that the mean
structural spacing is greater than 6 m,
118
Acknowledgements
Atlas Copco is grateful to BHP Billiton
and the management at Olympic Dam
mine for their kind assistance in the
preparation of this article.
NANJING, CHINA
Late starter
China began to stake a claim on the international mining map at the start of
the 1990s, with a determination to introduce mechanization, coupled with a
strong desire for reform and commercial success. Today, more than ten years
later, Chinese mines are reaping the
benefits that modern mining equipment
and methods can bring.
Shanghai Baosteel Group Corporation, a state-owned company set up in
1998, has an iron production of 20
million t/y. Amongst its suppliers is
Meishan iron ore mine, one of its subsidiaries.
Meishan is widely regarded as a model mine by the Chinese iron ore industry, and the equipment and methods it
uses, most of which are supplied by Atlas
Copco, are constantly being monitored
and adopted by others around the country.
Situated on the Yangtze River Delta,
some 320 km from Shanghai, Meishan
is the second largest underground ferrous metals mine in China, with raw
119
NANJING, CHINA
Development
Phase One of the Meishan development
plan comprised shaft development, underground stoping and sublevel caving.
There are six shafts, three for hoisting
(main, secondary and southwest), and
three for ventilation (south, southeast
1# Main shaft
+31.50 m
2# Main shaft
Southeast
ventilation
+37 m
North
ventilation
Shaft for
personnel hoist
+47 m
RAMP
186 m
198 m
198 m
213 m
228 m
243 m
258 m
330 m
447 m
120
NANJING, CHINA
1999
2000
2001
2002
2003
2004
2005
Development cu m
100,315
109,149
109,536
129,600
115,200
126,770
312,510
5+1 backup
6+1 backup
6+1 backup
5+2 backup
2.84
3.18
3.33
3.46
3.87
4.00
3.91
203
248
350
380
375
290
280
Number of employees
1,640
1,540
1,500
1,420
1,460
1,420
1,410
121
NANJING, CHINA
By the end of 2006, annual production for the Simba H252 and Simba
H254 was 60,000 m/rig, and the Simba
H1354s were producing 72,000 m/rig.
The capacity of the Boomer 281 was
1,700 m of drifts, and 1,900 m for the
Rocket Boomer 281, in faces 5 m-wide
and 3.8 m-high.
Long partnership
With more Atlas Copco equipment coming on stream, productivity will be
successively increased to meet new,
ambitious targets for the next phase of
development.
According to its plans for Phase Two,
mining will proceed down to a level of
420 m, and annual output will be increased to 4.2 million t of ore. The distance between the levels will be also be
increased, from 15 to 20 m.
Through its long partnership with
Atlas Copco, Meishan has also accumulated extensive experience of equipment
management and maintenance, where
the focus is on spot checks for cleanliness, lubricating, oil refilling, and
greasing. Atlas Copco service engineers
provide technical support, assisting on
scheduled maintenance and repairs, and
spare parts forecasting and stock planning. These combined efforts have led
to equipment availability close to 100%.
In addition, as Meishan is a showcase
of Atlas Copcos after sales service,
training for other customers operators
often takes place at this location.
Excavation equipment managers at
the mine state that, during more than
10 years of working with Atlas Copco,
they have been consistently provided
with equipment of correct design with
flexibility in operation, low energy consumption, high reliability, low pollution
and long service life.
Excellent after sales service, and
an abundant supply of spare parts, can
now be taken for granted.
Acknowledgements
Atlas Copco is grateful to the directors
and management of Meishan Iron Ore
Mine for their assistance in the production of this article, and to Baosteel Group
Corporation for permission to publish.
122
Otjihase, Namibia
Compartmented orebody
Otjihase, situated 40 km from the Namibian capital, Windhoek, employs 375
people, 160 of them underground. It
currently produces 35,000 tonnes of ore
per month. Its sister mine, Matchless, is
located 25 km to the east and together
these mines form Weatherlys Central
Operation. Some USD 40 million has
been earmarked for expansion work
during 2008.
The Otjihase orebody is best described as looking like a ruler, divided into
five separate compartments by a number
of faults. The longest of these extends to
8 km. In plan, the compartments form
a line from the surface in the north descending at a shallow angle to the south.
In section, the faults have displaced parts
of the orebody downward by varying
depths. The orebody averages a thickness of 5.5 m to 6 m, and is some 250
m wide, though the more southerly orebodies narrow to a width of about 60 m.
The main 250 m wide orebody has
been mined from the surface to an extent of 6 km. The first break in the orebody is the Otjihase fault, which gives it
Scaletec MC in operation.
OTJIHASE MINE
Karuma compartment pillar extraction.
Existing decline
Proposed declines to
Tigerschlucht compartment
Backfill barricades
Remaining ore pillars
Primary crushing is carried out underground, followed by secondary crushing and flotation. The concentrate,
containing 24% copper, is trucked to
Elize van der Merwe of EPS Mining is Otjihases Scaletec operator. The machine is really user friendly says
Elize, and it is simple to operate. She has been operating the machine for the last two months. Although
she had no prior training in operating heavy mining machinery, after a weeks training she was sufficiently
competent to take over the controls.
124
Decline
to surface
Grade control
In the Karuma Compartment, backfill
plays a key role in pillar extraction. The
backfill plant has been extensively refurbished. Fill is pumped underground
down two boreholes, and then allowed
to gravitate a further 2 km to the compartment.
The orebody dips 16 degrees northwest and plunges 6 degrees to the west.
As it is not homogenous, the mineralized zone presents challenges. The greatest variability occurs in a north-south
direction. To the north, there are highly
folded, magnetite quartzites. Grade control is more difficult in the north than
in the central and southern regions, due
to the erratic nature of the mineralization.
The northern edge of the orebody is
clearly defined, while at the southern
edge the ore needs to be sampled to determine the cut-off point. Both the
footwall and hangingwall are generally
well defined.
Thin, vein-like ore occurrences, or
stringers, in the hanging wall make rock
support work more difficult, and ventilation and moisture cause the sulphides
Mining methods in underground mining
5m
10 m
5% cement
5m
3. The central part of the pillar is recovered, leaving thin walls next to the
backfill.
The Cabletec, pictured here at the Otjihase mine, drills, grouts and installs cable bolts.
125
Two new Minetruck MT436B dumptrucks stand ready to be put into service.
Contour stoping
The mine uses room and pillar contour
stoping where all panels are mined on
strike, so that it is possible to cut diagonally across the orebody. To begin stoping, a panel, typically 5 m wide, is broken away followed by a second panel
immediately adjacent to the first.
These panels are typically about 100
m long, and take in the full height of the
orebody. Between each set of panels, a
10 m pillar is left. This primary phase
leaves an approximately-parallel set of
rib pillars. The first phase removes some
55% of the orebody, and after the pillar
removal phase the final extraction rate
rises to between 75% and 85%.
The plan is to extract the remainder
of the Karuma Block over the next four
years of production. With the Karuma
Block in production, Otjihase output will
126
Rock scaling
Where sulphide stringers are encountered in the hanging wall, they are blasted out. This increases dilution, but is a
small price to pay for the added safety.
As a matter of course, roof bolting is
From left, Victor VanWyk, Site Manager, Atlas Copco with Andrew Thomson, General Manager, Otjihase Mine, and Kobus van Tonder, Otjihases Mining Manager.
efficiency. The rig also has an electrically powered emergency reverse facility.
A turbo-charged, four cylinder, lowemission diesel engine allows the machine to tram at 15 km/hr on the flat.
While operating, four jacks keep the
machine stable. To date, operational availability of the Scaletec has exceeded
96%.
Cable bolting
A twin-boom Cabletec has been operating at the mine since April, 2007. Having two booms allows the operator to
drill support holes with one, while grouting and inserting anchors with the
other. A BUT heavy duty boom carries
a COP 1838 high performance rock drill
with its rod handling system, a combination that offers high-speed drilling
and excellent drill rod economy.
Mainly 7.5 m cable holes are drilled
with the Cabletec. The penetration rate
of 3 m/min means that 22 to 24 cable
anchors can be installed each shift. The
Cabletec has a really strong positioning
Ore handling
To increase the ore handling efficiency,
two new Atlas Copco Scooptram ST8B
loaders have been bought as well as
a third, secondhand unit to bring fleet
total to 10 units. These are matched to
127
An Atlas Copco Scooptram ST2D, more than 20 years old, is still going strong with no apparent oil/hydraulic leaks or excessive emissions at the Otjihase mine.
Acknowledgements
Atlas Copco is grateful to the management at Otjihase Mine for their assistance in the production of this article,
a version of which first appeared in
Atlas Copco Mining & Construction
magazine 1-2008.
Room and pillar layout at Waterval where Scooptram ST600LP loaders work in as low as 1.8 m headroom.
129
Production drilling
The layout at Waterval is divided into
12 sections with nine panels, or stopes.
Each panel averages 12 m-wide x 1.8
m-high, with pillars of approximately
6 m x 6 m. The drillers work three 8 h
shifts per day, six days a week and their
target per section is 23,000 t/month.
That translates to 200 t per panel, or two
panels per shift. Some 68-74 x 3.4 m-long
holes are required in each panel, taking
around 2.5 h to drill. Three 77 mm holes
form the cut, and the main round is drilled using Atlas Copco Secoroc model
27 R32 43-45 mm bits.
Ramps from the surface provide the
access for men, machines and supplies,
and also accommodate conveyor belts
for transporting the ore out of the mine.
The mine expects each Rocket Boomer
rig to yield around 200,000 t/year. For
rockbolting, 1.6 m-long Swellex bolts
130
Acknowledgements
Atlas Copco is grateful to the management at Waterval for their kind assistance in revision of this article and for
permission to publish.
KGHM, Poland
Geotechnical conditions
The formations are intersected by a
multitude of faults. An especially dangerous feature of the rock is its ability
KGHM, Poland
10 m
B
5m
A-A
D
10 m
B-B
7m
60
14 m
D-D
10 M
7m
9,5 m
C-C
7m
B-B
75
4m 10 m
60
12
10
m
8m
10
m
75
7m
C-C
7m
4m
14 m
5m
6m
4m
5m 5m
4m
A-A
~ ~7 m ~7 m 7~m 7~m ~ ~
~ ~
~ ~
~
14 m
14 m
~
C
~ ~ ~
~7 m 7~m 14~m ~
~
~ ~~
14 m
7m
7m
7m
Timber post
~21 m area
Dry backfill
3m
Thickness of
mineralized
zone
Room Pillar
KGHM, Poland
1-6
strengthened. The mine currently operates ten Atlas Copco rigs, and there is
a total of 16 Boomer rigs on the mines
as a whole.
The supplier service has been extended to include a drillmetre-based
contract for Secoroc Magnum 35 drill
rods and shank adapters and for COP
rock drills.
Working an effective 4.5 h/shift, one
Boomer drills 110-125 holes with hole
lengths varying from 3 m at the face
and 1.5-2 m at side walls and roofs.
Some of the Boomers feature the BSH
110 rod extension system to facilitate
drilling of 6 m stress-relieving holes.
In the first 8 months of 2002, one
Boomer drilled more than 58,000 holes
totalling 174,000 drill metres, with
availability of 92.6 %. Downtime comprised technical malfunctions 3.7%,
planned service 3.4%, and others 0.3%.
Room and pillar mining with roof sag
This method is especially suitable in
barrier pillars of drifts, heavily faulted
zones, and in direct vicinity of abandoned areas. Maximum allowable deposit dip is up to 8 degrees, and seam
thickness 3.5-7 m. The area is developed
133
KGHM, Poland
200-600 m
Residual pillars
A -B
Blasting techniques
Future plans
134
In the past, the mines tried to use dynamite, which is a water-resistant explosive
of high density and energy concentration. Due to the sensitivity to detonation,
and lack of possibility for mechanical
charging, dynamite is today almost
completely superseded by pneumatically charged ANFO. Initiation is by
electric delay detonators, coupled with
detonating cord in holes longer than 6 m.
Recently, electric detonators have been
successively replaced by Nonel. Bulk
and emulsion explosives are used in
room and pillar mining areas described
in the hydraulic backfill method above.
Acknowledgements
Atlas Copco is grateful to KGHM management for their inputs to this article,
and in particular to the authors of its
book on the technical evolution of the
Polish copper mining industry:
Jan Butra, Jerzy Kicki, Michal Narcyz
Kunysz, Kazimierz Mrozek, Eugeniusz
J Sobczyk, Jacek Jarosz, and Piotr Saluga. Reference is also made to Underground Mining Methods Engineering
Fundamentals and International Case
Studies by William A Hustrulid and
Richard L Bullock, published by SME,
details at www.smenet.org
Units
Boomer S1 L
Rocket Boomer S1 L
26
Scooptram ST1520
Scooptram ST1520LP
Germany/South Korea
Case studies
The major characteristic of a successful underground mining operation is its
efficiency, and the single greatest factor
affecting this is the cost of drilling and
blasting. Atlas Copco drill rigs are
bringing down this cost by a combination of drilling speed and accuracy
with low maintenance and longevity.
Matching the drill rig to the job ensures
that, whatever the mining situation,
economic long-term production can be
achieved, sometimes with the whole
operation dependent upon a single machine. The following case studies from
four very different locations serve to
underline this point.
Auersmacher, Saarland,
Germany
Since 1936, almost 20 million t of limestone have been produced at Auersmacher, a border town in Saarland,
Germany. The mining area covers almost 4 sq km, with overburden of approximately 50 m in thickness and an
average mining height of some 6 m. The
Triassic strata comprises a shelly limestone, which is excellently suited as an
aggregate for the local steel industry.
The mine is working a room and
pillar system of extraction in the horizontal deposit, and the normal face is
5 m-high and 6.5 m-wide. The length
of a room plus pillar is about 100 m, in
which some limestone is left to form
the permanent roof.
A diesel-powered computerized
Atlas Copco Rocket Boomer L1C-DH
hydraulic drill rig is used because there
is no electricity supply installed to the
faces. It is equipped with a COP 1838
rock drill with 22 kW output. As a result, blast holes of 51 mm diameter can
be drilled to depths of 3.4 m at a rate
Germany/South Korea
136
Obrigheim,
Neckarzimmern, Germany
Heidelberg Cement employs some 37,000
people at 1,500 sites in 50 countries, a
truly international company with sales
in excess of EUR6.6 billion.
Since 1905, the company has been
operating an underground mine in
Obrigheim producing gypsum and anhydrite. This operation is only possible
thanks to the use of percussion drilling
technology provided by an Atlas Copco
computerized Rocket Boomer L1C
drill rig introduced in 2003. Training
for operators covering drilling, systems
and maintenance was provided by Atlas
Copco, leading to excellent results and
high utilization.
Production is by room and pillar,
with 10 m-wide x 5.5 m-high drives. A
4.5m-deep round comprises four cutholes of 89 mm-diameter and 60 blast
holes of 45 mm-diameter. Much work
has been put in by both the mine and
Atlas Copco to optimize the drill pattern
to maximize the pull of each round.
The rig is equipped with a heavy duty
COP 1838HF rock drill, and hydraulic
systems and onboard compressor are
driven by a 75 kW electric motor. The
diesel engine is used to move the rig
around the mine. A water tank with
water admixture device provides the
flushing medium for drilling.
Penetration rates vary considerably
due to the large range of compressive
strengths of gypsum and anhydrite,
Mining methods in underground mining
Germany/South Korea
Josefstollen, Trier,
Germany
Josefstollen mine was opened in 1964
and produces some 600,000 t/y of raw
dolomite primarily for the building materials industry. Operating company
TKDZ has some 40 million t of reserves
at its disposal, enough for another 40
years of mining.
The dolomite is of excellent quality,
with a compressive strength of 130-150
Mpa, and optimized underground production allows the products to be placed
on the market at competitive prices.
Mining is by conventional room and
pillar at two gallery levels in the bottom
and central beds. The production area is
initially opened up by mining horizontal galleries, with ramp access to the
individual beds. Room widths are 5 m
in the bottom bed and 5.5 m in the central bed, with heights of 5.0-5.5 m.
Each blasting round comprises 29
off 3.3 m-deep x 45 mm-diameter
holes with a Vee cut. Around 13 faces/
day must be drilled to keep pace with
demand.
Drilling is carried out by a dieselhydraulic Rocket Boomer L1 C-DH rig
equipped with COP 1838HF rock drill
and air-water mist flushing. The rock
drill takes around 25-30 seconds to
drill each hole, at a penetration rate of
8 m/min. Total drilling time is about 30
minutes for each round.
The dolomite is difficult to drill because it is not a continuously compact
formation, so the computerization on
the drill rig, which controls both the
hammer and feed, plays a vital role. As
a result, most of the required drilling
is completed on a single shift, with the
second shift offering flexibility for drilling awkward places and for performing
maintenance. The mine also sees this
Rocket Boomer L1 C-DH with COP 1838HF rock drill achieves 8 m/min at Josefstollen.
The strata is a middle limestone member of the Gabsan formation in the upper
palaeozoic Pyeongan super group of
minerals. The geological structures are
mainly controlled by a NW-SE trending, with westerly overturned folds and
thrust faults.
Reserves confirmed by drilling are
over 12 million t, of which it is expected
137
Germany/South Korea
Conclusions
7m
Pillar
9m
Pillar
tlas
ock
Co
R
pco
000
B, 2
ls A
Dril
138
Acknowledgements
Atlas Copco is grateful to the managements at Auersmacher, Heidelberg,
TKDZ and Yongjeung for their inputs
to this article and for permission to
publish.
Underground geology
Located in the city of Andorinha, around
100 km from the Pedrinhas mine, the
companys underground operations have
been developed within the Medrado/
Ipueira deposit.
This is one of several chromite-mineralized intrusions in the Jacurici Valley
in the north-east of the So Francisco
Craton, which hosts Brazils largest
chromite deposits. Being irregular and
fractured with numerous faults, the deposit presents a considerable geological
and mining challenge.
The Medrado/Ipueira deposit is divided into several mining areas. There
are the Medrado mine and the Ipueira
mine, the latter of which is divided into
five working areas: Ipueira II, III, IV, V
and VI. Currently, besides Medrado,
only Ipueira II, III, IV and V are operational, whereas Ipueira VI is a future
expansion project. The underground mines have been in steady operation since
1977. In 2004, Ipueira produced 450,000 t
Underground exploration
The company is always looking for the
best way of doing things in consultation
with workers, technical consultants and
through visits to other mines. The consultation process also includes manufacturers of mining equipment, with which
Ferbasa discusses the best technological
options for its operations. This consultation process is very important for the
mine, in order to help maintain a high
level of modernization.
From a geological point of view, the
Medrado/Ipueira orebody represents a
challenge. With an average thickness of
8 m, and 500 m-long panels, the orebody
is irregular and fractured with numerous faults. The accurate delineation of
the orebody is very important, and to
this end the geology department has to
carry out a great deal of exploration
drilling. The main machine employed in
this key task is an Atlas Copco Diamec
U6 exploration drill rig equipped with
Sublevel caving
The main underground mining method
employed is longitudinal sublevel caving, though open stoping is also used
in some areas of Ipueira, depending on
the layout of the orebody. When the orebody is vertical, sublevel caving is used
139
Production loading
N 55
Production
N 65
Production drilling
N 75
Mucking out
N 85
Development
Charging
N 95
Scaling
N 105
Drilling
N 115
Shot
creting
N 125
The locations of drifts and drill patterns are adapted to the ore-waste boundaries.
Blast holes
Cable
Ore
Waste
Drift
2.2 m
140
Slot drilling at Ferbasa: The Simba M6 C in action and, (right), the perfectly finished row of holes.
Slot drilling
One of the main challenges at Ferbasas
underground operations is the development of inverse drop raises. These openings, which are also called blind raises
because they dont communicate with
the upper level, can only be accessed
from the lower level. This limitation is
dictated by the mining methods.
Previously these blind raises were developed upwards by successive individual
Acknowledgements
Atlas Copco is grateful to the managements at both Ipueira and Medrado
mines for their contributions to this
article.
141
142
Zacatecas, Mexico
Mechanization pioneer
The official name of the Proao mine
comes from Captain Diego Fernandez
de Proao, who discovered the site and
developed the first mining works on the
hill that bears his name. The operation
is also known as Fresnillo mine because
of its proximity to Fresnillo city. It is
run by the Compania Fresnillo, SA de
CV, which is 100% owned by Peoles.
With a history that can be traced as far
back as the 1550s in Pre-Hispanic times,
Proao has gone through a number of
phases, which have left an important
mark on the mine. Its operations have
been stopped due to economical and
technical difficulties (1757 to 1830), as
well as during the Mexican Revolution
(1913 to 1919), and inevitably it has gone
through several ownership as well as
technological changes.
From employing basic manual tools
in the early days, the mine now employs
modern mechanized units, including
some of the most sophisticated mining
machinery available.
Embracing mechanization early on
has been one of the factors that has helped Proao cement its position as the
world's largest and most profitable silver
mine. They started mechanizing operations about 40 years ago, and during the
Production expansion
During the mine's long history it has
had to adapt to changes in the geology
and work parameters. For instance, the
mining method has had to be fundamentally changed several times, and
each time the appropriate technology
and equipment has had to be introduced.
Atlas Copco has worked alongside the
mine management for several years to
adapt and innovate with primary equipment, service, training, inventory management and parts stock. The mine recently implemented a substantial production increase, going from 4,500 t/day
to 7,000 t/day. To support this production expansion the company recently
increased its mining fleet with the purchase of three Rocket Boomer 281 development drill rigs additional to its
four existing units, another Simba M4 C
production drill rig additional to its existing three units, five Scooptram ST1020
loaders to complement its existing fleet
of 17 units, and two Minetruck MT2000
trucks to increase its fleet to seven units.
Atlas Copco has also started a service
contract for the Simba rigs, which requires the presence of four technicians
on site, and offers similar assistance for
the loaders.
Currently, the Proao mining fleet
represents a mix of old and new Atlas
Copco technology. Amongst the old units
are Scooptram ST6C loaders, BBC 16
pneumatic rock drills, BMT 51 pusher
leg rock drills and DIP & DOP pneumatic pumps. There are also Diamec U6,
Diamec 262 and Diamec 252 exploration drill rigs, Boltec 235 bolting rigs,
Rocket Boomer 104 drill rigs, Simba
1254 production drill rigs and Robbins
143
Zacatecas, Mexico
USA
G
f
u l
o f
M E X I C O
a
f o
l i
G U L F
O F
M E X I C O
r n
Zacatecas
i a
Mexico City
BELIZE
GUATEMALA
HONDURAS
EL SALVADOR
Mining operations
The underground operations can be accessed either through two shafts, Central
Shaft and San Luis Shaft, or by one of
the mine's several ramps. The mine has
seven levels and in Level 425 is the San
Carlos orebody, which currently produces 67% of production.
Proao carries out about 40,000 m
of development drilling a year. To support this work, there are three different
contracting companies: Mincamex, Jomargo and Mecaxa. All three companies own Atlas Copco equipment,
mainly Rocket Boomer drill rigs and
loaders.
The mining method is cut & fill using
upwards and downwards drilling. However, the amount of drilling and the hole
diameter have changed over the years.
144
Zacatecas, Mexico
4915
4600
750
1500
750
380o
mine with reserves of gold, silver, copper, lead and zinc, FIM's main products
are zinc concentrates and lead concentrates. At the end of 2005, the mine had
reserves of 27.5 million t with an average zinc grade of 3.3% and 0.74% of
lead.
With an investment of US$125.8 million and a production capacity of 8,000
t/day, in 2005 FIM produced a total of
65,948 t of zinc concentrates and during
the first semester of 2006, produced
Rocket Boomer L2 C drill rig with COP 1838 rock drills at Madero mine.
New operation
Located about 15 km north of the city of
Zacatecas, Francisco I. Madero (FIM)
is one of Peoles' newest mines, having
started commercial production only in
2001. The mine's name comes from a
former Mexican President, Francisco
Ignacio Madero, killed during the Mexican Revolution. Although a polymetallic
Mining methods in underground mining
145
Zacatecas, Mexico
Personal service at Proao: left, Antonio Gonzales, mine captain, San Carlos area, with
(far right) Rufino Molina, Atlas Copco drill master and Simba rig operators.
Maintenance
To deliver its maintenance contract,
Atlas Copco has its own facilities at
the mine, backed up by the distribution
and service centre in Calera. The contract includes preventive and corrective
maintenance, and follows a programme
already prepared for all the Atlas Copco
fleet.
The service contract has a specific
programme every week depending on
the machines to be serviced. About 50%
of the machines have been working for
between 18,000 and 20,000 hours without any rebuild, which is a good reference for the quality of the equipment.
The contract also involves operator
training.
Acknowledgements
Atlas Copco is grateful to the mine managements at Proao and Madero and
directors of Peoles Group for their
inputs to this article and for permission
to publish.
Mining methods in underground mining
Introduction
The Panasqueira mine is located at Barroca Grande in a mountainous region of
Portugal, 300 km northeast of the capital city of Lisbon, and 200 km southeast
of the port city of Porto.
The mining concession lies in moderately rugged, pine and eucalyptus covered hills and valleys, with elevations
ranging from 350 m above sea level in
the southeast to a peak of 1,083 m above
sea level in the northwestern corner.
The concession area is an irregular
shape trending northwest-southeast, and
is approximately 7.5 km-long. It is 1.5
km-wide at the southeastern end, and 5.0
km-wide at the northwestern end, where
the mine workings and mill facilities
are located. The geology of the region
is characterized by stacked quartz veins
that lead into mineralized wolframbearing schist. The mineralized zone has
dimensions of approximately 2,500 m
Production levels
Access to the mines main levels is by
a 2.5 m x 2.8 m decline from surface,
with a gradient of 14%. The main levels
consist of a series of parallel drives that
are spaced 100 m apart, and which provide access to the ore passes for rail
transport, and connect with ramps for
movement of drilling and loading equipment.
There are seven veins between the 2nd
and 3rd Levels, which are 90 m apart.
The veins are almost flat, but occasionally split or join together. They pinch
and swell, and are usually between 10
and 70 cm-thick, and can plunge locally
Mining method
The stoping process begins when spiral
ramps are driven up to access the mineralized veins, and the orebody is opened
in four directions and blocked out.
Initial pillar
Final pillars
11 m
148
5m
3m
5m
3m
Wolframite seam
the blast holes, and electric delay detonators along with small primers are
used for blasting. Blasting takes place
around midnight, and the mine then ventilates throughout the night.
Each blasted face produces about
60-65 t of rock, and each rig can drill
up to 10 faces/shift, depending upon the
availability of working places.
After the blast, the muck pile is washed down, and the back is scaled. Ore
is loaded and hauled by the Scooptrams
from the headings to the orepasses.
Once the limits of the stopes are
established, then the final extraction
takes place with 3 m x 3 m pillars
created from the perimeter retreating
to the access ramp.
Drilling performance
The mine drill rig fleet comprises three
Atlas Copco Boomer H126 L drill rigs
mounted with COP 1238ME rock drills;
five Atlas Copco Rocket Boomer S1 L
low-profile drill rigs mounted with
COP 1838ME rock drills; and three
older drill rigs retrofitted with COP
1238LP rock drills.
Mining methods in underground mining
149
Scooptram ST600LP
Each Scooptram ST600LP cleans 4-6
headings/shift on a maximum 200 m
Main access ramp to level 2 at Panasqueira mine.
Acknowledgements
Atlas Copco is grateful to the directors
and management at Panasqueira for
their kind assistance in the production
of this article, and for providing access
to the mine statistics.
150
notes
151
Notes
152
www.atlascopco.com