Post on 02-Jun-2018
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Impressive Output
Svea North is located some 40 km from
Spitsbergens main town of Longyearbyen,
and there is a fully-functioning mine
encampment at the site. There is no road,
and the only access is by boat in summer,
snowmobile in winter, or by the daily
flights into the airstrip.
Despite its remote location, Svea North
produced an output of nearly 2.7 million t
from its single longwall face in 2003.
Indeed, in October, 2003, the mine pro-
duced a creditable 460,000 t, taking it to
the number one position in Europe.Average output per miner of 75 t/shift
makes it one of the most efficient under-
ground coal mines in the world.
The seam averages 3.8 m thick, with
few geological faults, and good overall
conditions. It lies under 400 m of rock and
200 m of ice at its deepest, while at its
shallowest point, there is just 50 m of rock
between the coal seam and the glacier. The
estimated coal reserve is 40 million t, of
which SNSK expects to mine something
like 32 million t. It is a very marketableproduct at 32 MJ/kg, with a low ash
content of 5%, and a low sulphur content
at 0.6%.Svea North is accessed by simply
driving into the drift in a conventional
four-wheel drive vehicle.
SPITSBERGEN, NORWAY
FACE DRILLING 43
Tunnelling Beneath a Glacier
Record PerformanceSpitsbergen, a Norwegian archipel-ago located in the Arctic ocean some12 degrees south of the North Pole,was first mapped officially by Dutchsailor Willem Barents in the late16th century. Russian geologist, VARusanov, discovered extensive coaldeposits in 1912, which are currentlyexploited under an internationaltreaty. Svea North mine, developedin 1999, is located beneath a glacier,over which owner SNSK has had tohaul its output along an ice roadto the port area. The solution was to
drive a tunnel beneath the glacierand replace trucks with conveyor. Inthis remote and harsh location, con-tractor Leonhard Nilsen & Sonner(LNS) needed reliable equipmentwith good manufacturer support.They chose an Atlas Copco RocketBoomer L2 C drillrig, and not onlycompleted on time, but also broke afew tunnelling records along theway!
Svea North is accessed by sea during
the summer.
Charging the face from the rig basket.
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Since production commenced, a com-
bination of on-off highway trucks and
ADTs has hauled the coal the 6 km or so
from the stockyard at the pit entrance to
the port area, making up to 50,000journeys/year.
As the fjord freezes during winter, the
coal is kept in a 1.6 million t-capacity
stockpile beside the port until the ships can
again make their way to the dock.
Keeping an ice road open in such a
climate is not easy, with around NKr 5 mil-
lion/year spent on grading alone, to main-
tain the required capacity of 16,000 t/day.
The wear and tear on trucks and loading
equipment added greatly to this bill,
making it imperative that an alternative
solution be found.SNSK decided to replace the ice road
with a tunnel under the glacier. The 2.6%
dipping tunnel alignment lies beneath the
production seam, and it is designed to house
both a conveyor system, and a channel to
drain ground water percolating through the
mine from a lake beneath the glacier.
The mine has suffered problems with
excessive water, despite its powerful
installed pump station and lengthy
pipelines. Water ingress is greater in
summer because of the thaw, evidenced bythe longwall being put out of action by
flooding for much of July and August,
2002.
Tunnel Drivage
LNS was awarded the contract for the
5.6 km-long x 38 sq m tunnel, and started
its development in November, 2002, using
a new Atlas Copco Rocket Boomer L2 C
drillrig. Planned advance of 100 m/week
was easily exceeded, with a world
drill/blast record of 150 m being achieved
in the best week.
This rate of advance is normally
achieved using TBMs, and is extremely
significant for a drill and blast operation
because of the dramatic difference in capi-
tal employed.
Rock conditions are relatively soft,
competent and not generally abrasive,although there is some quartzite intrusion.
LNS used 48 mm bits with three holes in
front and ballistic buttons, which lasted
from 300-500 m before regrinding. For
each round, the blastholes were drilled to
depths of 5 m and took around 1.5-3 min-
utes apiece, with 75-76 holes required for
a full pattern. Productivity was kept at a
high average rate, with LNS achieving 3-4
rounds/day, and sometimes five. In the
worst conditions, this dropped to two
rounds/day.For charging the upper holes and the
cut, the Rocket Boomer was equipped with
a Dyno hose charger mounted in the
basket. With this device it was possible to
regulate the volume of explosives injected
into each hole. A second hose was used
manually for charging the holes in the
lower part of the face, without the option
to regulate the volume of explosives
injected. A standard emulsion explosive
was used, mixed in the hole and detonated
using Nonel. Emulsion explosives are
more expensive than ANFO, but theirmuch-reduced blasting fumes allow opera-
tors to return to the face quicker after each
blast. Another advantage is that emulsion
components can be transported under the
flammable material rules, and are not
classified as explosive until they are in the
hole.
The mucking operation took around
1.5-2 h for around 380 t of blasted rock. A
conventional loader was used, with a fleet
of six trucks, with a grader keeping the
roadway clear and smooth. A face crew ofsix was sufficient for each of the two
SPITSBERGEN, NORWAY
44 FACE DRILLING
Atlas Copco Rocket Boomer L2 C at the
face.
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shifts/day, while the total LNS crew on this
project was 52.
The tunnel was started in permafrost,
with a 400-500 m transition zone at each
end to reach solid rock. In these zones,
melting ice caused problems with the shot-
crete application. LNS employed an accel-
erant in the shotcrete mix, and reinforced it
with steel fibres. Two rockbolts were gen-
erally required for each metre advance, but
problems with rock pressures sometimes
necessitated more extensive bolting, and
use of a hydraulic scaler. Polyester roof-
bolts were replaced by 2.4 m and 3 m
Swellex Manganese bolts in some of the
more difficult areas.
The drill and blast portion of the tunnel
project is now complete. Fitting out, and
installation of the ventilation and conveyor
systems, should be finished by the end ofthe first quarter of 2004.
Equipment Modifications
The Rocket Boomer L2 C drillrig was
fitted with Atlas Copcos ABC Regular
control package, which indicates the hole
positions, but does not include full-function
automatic boom movement.
The contractor has had experience using
a computerized Rocket Boomer XL3 C on
the Norwegian mainland, but it was still amajor decision to send an RCS drillrig to a
remote location like Spitsbergen. During
commissioning, Atlas Copco provided
three or four days of basic training at site
to the new operators. The instructor then
remained in support for another three
weeks, and returned some months later for
a week of follow-up training. The contrac-
tor has taken care of maintenance and
operation of the rig during the entire pro-
ject using his own people, without the need
of outside assistance.
In the transition zone between the per-mafrost and the rock, it was found that the
conventional anti-jamming system fitted to
the drillrig did not give sufficient warning
of jamming, resulting in some rod damage.
Atlas Copco suggested an alternative pro-
gram, which suited the conditions better by
simultaneously monitoring rotation, feed
rate and water flow. This resolved the
problem, and there were no more instances
of rod damage caused by jamming.
By agreement with LNS, Atlas Copco
evolved a package of spares suited to theremoteness of the operation. However,
reliability was good, and only the usual
service parts such as filters and hoses were
required.
The SNSK mine also has an Atlas
Copco Swell bolter, originally supplied in
1986. This rig was rebuilt in 2001 and
equipped with the new HBU bolting unit
with a COP 1028 hydraulic rock drill. This
bolting unit is used in parts of the mine
with hard sandstone layers, where rotary
drilling cannot be used.
Svea Norths future looks good. The
mine has a projected life until 2013, andthere are another two deposits of 3.5
and 2.7 million t nearby that SNSK may
wish to develop. The company is also car-
rying out exploration work elsewhere on
Spitzbergen.
Acknowledgements
Atlas Copco is grateful to SNSK and LNS
for permission to publish this article,
which is derived from a site report written
by Mike Woof, editor of World MiningEquipment magazine.
SPITSBERGEN, NORWAY
FACE DRILLING 45
Rockbolts and shotcrete provide the
main support.