CRADLE TO GRAVE
A CAP FOR ILLEGAL MINING
Redundant mine shafts are becoming a growing risk for large
mining houses due to a sharp spike in illegal mining activities.
Illegal miners are willing to risk their lives by going underground
to try and recover pockets of unmined material, as well as
copper cable and steel shaft infrastructure. According to André
Botes, Jet Demolition contracts manager, it is not uncommon to
witness extreme violence or intimidation in these areas.
The most effective means of ensuring that redundant shafts
are protected from occupation by illegal miners is to seal them
permanently below natural ground level (NGL), typically after
filling the shaft barrel. Here is where specialist demolition
contractor Jet Demolition stands to play a vital role.
Illegal mining activities are stemmed by plugging old shafts.
Its turnkey service offering for the mining industry includes
backfilling shaft barrels, designing permanent caps, installing
caps at a defined depth below NGL, and recording the final
position and depth of caps, followed by the backfill and
reinstatement of the natural material over cap tops.
Mining houses typically require such a turnkey service for
two main scenarios: Firstly, to seal the shaft permanently as a
mitigating factor, thereby preventing unauthorised access by
illegal miners or, secondly, to rehabilitate the mining footprint
fully, rendering the area safe for public use.
Another challenge is that various shafts are often
interconnected, such as a live shaft and a redundant shaft
linking together hundreds of meters below NGL. “It is thus
critical to ensure that we understand the network we are
operating in, so that our capping and sealing activities do
not influence or adversely affect miners underground in a
neighbouring shaft,” says Botes.
The main requirement for permanent shaft sealing and capping
projects is to ensure full compliance with the Mine Health and
Safety Act, and the provisions of the Department of Mineral
Resources, the approved Environmental Management Plan, as
well as any client-specific requirements.
The natural surrounding environment also has to be considered,
paying special attention to natural water courses and
stormwater management. This could mean rerouting natural
water courses slightly, while ensuring there is no subsequent
negative downstream effect. All material used to fill shafts must
be clean and uncontaminated. This is vital to ensure that no
groundwater contamination will occur after sealing.
“We have also sealed a few shafts that had to be equipped with
monitoring access points as part of the Acid Mine Drainage
(AMD) project in the Western, Central and Eastern Basins of the
Witwatersrand Goldfields in South Africa. These access points
will be used to monitor the quality and volume of subsurface
water in the foreseeable future,” says Botes.
Casting of high-slump concrete to shaft.
THE BEAUTIES OF BLACK
MOUNTAIN
Robust exploration drill rigs are a necessity in the diverse
and often rough terrain of the Northern Cape. Vedanta
International’s Black Mountain mine, close to the town of
Aggeneys, recently appointed Hall Core Drilling to carry out an
exploration programme in the area. The company deployed
two drill rigs, one in a valley and the other one higher up on
the mountain.
The rig used in the valley is an older model of the surface core
drilling rig, Boyles C6C, from Epiroc. This rig typically drills 200m
deep holes in a few days and is then moved to a new location
in the valley. The hole depth and the distance between holes
are determined by the geologist, who also analyses the core
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African Mining Publication
samples retrieved by the four-man drilling crew. The team
consists of two assistants, a corewriter and an operator.
An Epiroc Boyles C6C drill rig, which features a two gear
Durahead rotation unit, drills holes up to 400m deep. "These
rigs are really up to standard. The new Durahead rotation unit
is much better that what we have seen before and the whole
rig is stronger, better designed and with fewer problems. You
really get a lot of bang for your bucks with this rig," says Hennie
Eybers, site supervisor at Hall Core Drilling.
The Durahead rotation unit, manufactured in Sweden, doesn’t
have a chain. It has only a high and a low gear which makes life
easier for drillers. Furthermore, the machine has an effective seal
that prevents water and mud from entering the gear box, which
is a real reliability booster. This rotation unit is easy to service
thanks to the seven grease fittings and the position of the lube
oil filters.
African Mining
African Mining February 2020
47