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CONSTRUCTION WORLD
SEPTEMBER
2016
GEOTECHNICAL
South Africa have some of the
deepest mines in the world, so
you can imagine the amount of
roads/tunnels criss-crossing the
earth below our feet. To protect people and
equipment, the tunnels are lined with mesh.
In some mines, Geobrugg’s high tensile steel
mesh (breaking load of 1 770 N/mm
2
) had
been used for ground support in the tunnels.
The majority of the tunnels in the gold and
platinum mines, have for years and continue
to do so today, been safeguarded with mild
steel (breaking load of 500 N/mm
2
) and lacing
as the preferred method for roof support.
South Africa’s other commodities
like iron ore and copper are mined on the
surface. And even though the environmental
challenges for surface or open pit mines are
different, they still require safety measures
to protect their most valuable assets – the
workers and the equipment. Even though
the roads inside an open pit mine are not
numbered P, R or N, and probably don’t
appear on Google Maps, they can’t be
neglected as they ensure that the operations
of the mine run smoothly.
A typical open pit mine has pit walls that
are excavated at an angle and the walls are
stepped/benched. The benches vary between
8-12 m in height and 4 to 8 metre in depth,
depending on the size of the machinery that
will be used. These benches help prevent
rocks falling all the way down the entire face
of the wall. Sometimes additional rockfall
mitigation measures are required. More and
more companies are looking for solutions
that have less impact on the environment
and are more cost-effective. Geobrugg’s
range of products provide rockfall mitigation
solutions that are not only aesthetically more
pleasing, but are easier to install and more
cost-effective.
Situation at Rio Tinto
Towards the end of 2015, Fairbrother
Geotechnical Engineering approached
Geobrugg to help them with a design solution
at Rio Tinto’s Rossing Uranium Mine near
Swakopmund in Namibia. Extensive blast
damage within the sub-drill area have left the
rockmass on the particular access ramp to
comprise of loose rocks and jointed blocks
that hung precariously along the crest of
the bench face. This situation is a potential
source for rockfall. The low catch capacity
in certain parts of the slope posed a risk to
equipment and possible injury to people.
This would lead to increase in production
cost. Although temporary measures to
mitigate the risk had been put in place by the
mine, they required a long-term solution to
adequately minimise danger posed by the
rockfall hazard.
Solution provided
Considering the geological condition at the
mine, a draping system was recommended.
This option would not only proof cost
effective, but would be an efficient solution
to ensure that the trolley line is protected
from rockfall. The draping system comprising
15 000 m
2
of Geobrugg’s QUAROX PLUS®
mesh was installed by Fairbrother’s trained
specialists. The wall in question was approxi-
ECONOMICAL SOLUTION
to rockfall protection
When we think about
mining, the picture of a
worker with hard hat,
overhaul and gumboots
comes to mind. He
is usually working
underground in a tunnel
hundreds of metres below
the earth’s surface.
View of the QUAROX® PLUS nets with pit underneath.
mately 110 m high and 270 m long and easily
accessible via a haul road. Enough room
for installation of anchors to pin down the
draping system, was present. The secondary
mesh on the QUAROX PLUS® rolled cable
nets are factory pre-installed. The Geobrugg®
Supercoating finish on the cable nets gives
it three times longer lifespan than hot dip
galvanized cable nets.
The slope draping solution used at Rio
Tinto’s mine is a combination of DELTAX®
mesh (secondary) and QUAROX® rolled
cable nets (3,9 m x 30 m per roll). The
superior qualities of QUAROX® rolled cable
nets compared to conventional cable nets,
allowed for easier and more efficient installa-
tion. No extra work is required before
GBE barrier during installation showing mesh panels pre-installed at factory.
QUAROX® PLUS draping system is a cost-
effective mitigation solution.
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