Nowadays the production
at the mine is solely based on tunnel work, since the old method on shrinkage
stopeing was abandoned. As mentioned in our historic summary the main
production takes currently place at level 86z ( z=meters above sea-level).
Here the mine extends over a distance of 3 km, and the main part of the
limestone at level 86z and above has been removed by shrinkage stopeing.
But at both ends of the mine we will now recover limestone at several
levels, all the way up to the surface. In the western part of the mine the
exploitation takes place below the old "Sjøflot" mine, which is
located at level 160z and extends over a distance of about 1 km. By
accessing new levels at 12 meters intervals we will eventually exploit the
2 mines together. At the same time we will continue to work our way
downward to level 10z. Here the limestone remains untouched over the mine's
entire extent and mining will mainly take place here. The reserves extend
from "Årnes" in the west, where the limestone vein disappears
into the sea, and east to "Rindalen" valley at a distance of 30
km. This implies based on a conservative estimate, that some 150 million
metric tons of limestone are located here, but the quantity may as well be
in the order of 500 million mt.
We own 2 diesel
hydraulic Atlas Copco tunnel-rigs. This entails significant savings in
rigging costs and -time since the mine extends over such a large area and
the drilling sites are located far apart. First a 4 x 7 meter pilot tunnel
is drilled. Thereafter the remaining limestone width is stoped. The average
tunnel size becomes some 7 meter in height and 15 meter in width.
For blasting purposes we
own a specially constructed rig with a lift and air-compressors to blow the
powder explosive (anfo) into the drilled holes. Ignition takes place by
means of nonel-bade millisecond percussion caps.
After the blast, loose
rock is removed by means of a hydraulic hammer and after this has been done
no loose stones remain so that it is not necessary to bolt the remaining
Loading is carried out
by means of 20 mt GHH mine loaders and the stones are conveyed to the silo
by means of Volvo-dump trucks. With transport distances approaching 3 km
one way, it is necessary to maintain an adequate road standard. For this
purpose we operate a 5 mt Gehl-scraper, witch uses rubble from the mine as road
The first stage of the
crushing process is carried out in a crusher witch is located inside the
mountain between the levels 10z and 86z. First there is a mine silo with a
storage capacity of 1000 mt, which is sufficient to cover the daily
capacity of the cruching unit. The first unit is a 250 mt German Humbolt
jaw-crusher. The size of the jaw is 1,20 x 1,40 m. The limestone is further
crushed in a 50 mt cone crusher. A vibrating Svedala screen, screens the
limestone before it is stored in silos witch are located inside the mountain.
Three fractions have been obtained by then: 0-8, 8-25 and 25-80 mm.
Transport to the quay is by means of a conveyer belt.
The second part of the
crushing process takes place at the quay. A 36" Morgaardhammer crushes
the limestone into smaller fractions. Storage of finished product takes
place in five silos with a capacity of 500 mt each. On top of the silos
there is a screening plant witch splits the material into the fractions
0-1, 1-3, 3-8, and 8-16 mm. We also have a storage building where we store
0-1 mm agricultural limestone, and open-air storage areas for 0-3 mm coarse
agricultural limestone, 3-8 mm gravel and 0-8 mm rubble.
At the quay we also bag
limestone in small - and big (portabulk) bags.
Finished product is
dispatched by truck or loaded on vessels.