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COVER STORY
22
MODERN MINING
November 2016
now largely complete. In addition, the project
involves the upgrading of the ventilation infra-
structures; improvement and modernisation of
the underground ore handling infrastructure to
facilitate ore flow, storage and sorting efficiency;
upgrades to the Nchwaning II surface plant
infrastructure (not in WorleyParsons’ scope);
and the reinstatement of the Nchwaning I mine.
In Greyling’s view, one of the highlights of
the BRP has been the sinking of the new 5,5 m
diameter, 167 m deep, concrete-lined ventila-
tion shaft at Gloria. “The main challenge was
that the sinking had to take place through
Kalahari sand, as well as calcite, red clay and
conglomerate before the shaft entered the
more competent tillite formations,” he notes.
“Because of the Kalahari sand, we introduced
perimeter piling to a depth of 35 m. In addi-
tion, dewatering holes and cementation of the
areas just above the clay formations reduced
the influx of water into the shaft and prevented
excess disturbance of the clay during the sink-
ing process.”
The sinking was delayed slightly in the slow
sink phase due to the soft ground conditions.
To mitigate the time lost, the contractor agreed
to implement a continuous operations cycle
during the main sink phase until completion of
the station cutting.
Additional precautions were taken to pre-
vent any delays while sinking through the clay
formations. During this process it was impor-
tant to keep the lining as close to the shaft
floor as possible to minimise contact with air
and moisture. Any stoppage – due to a Section
54 notice, for example, being applied to the
mine – would have had severe consequences.
Fortunately, the sinking portion of the project
was completed without incident.
Once the shaft entered the competent tillite
formations, normal sinking took place (from a
depth of 71 m to 167 m). The sinking stage was
designed to accommodate ‘Hong Kong’ drills.
This methodology reduced the need for people
on the shaft bottom.
Cleaning was carried out using an excavator.
Corrugated steel rings were used for temporary
support in the shaft and the cycle ensured that
the lining was never more than 4 m from the
shaft floor.
The contractor, Murray & Roberts Cemen
tation, worked for more than a full year (400
days) without a lost time injury. “Taking into
account the high risk nature of the work it per-
formed, this was an excellent achievement,”
comments Greyling. He adds that prior to
sinking Gloria, Murray & Roberts Cementation
had worked on another shaft of similar dimen-
sions in the Kalahari Manganese Field (KMF),
and thus had some experience of the difficult
ground conditions characteristic of the area.
Greyling points out that the successful com-
pletion of the shaft reinforces the reputation of
WorleyParsons as a world leader in the design
and implementation of shaft projects. He adds
that WorleyParsons RSA has been the EPCM
contractor on the majority of shafts under-
taken in South Africa in recent years. These
have included Impala 17 Shaft, as well as the
shafts at the Styldrift and Bakubung platinum
mines and the Shondoni coal project. A current
flagship contract is the Venetia Underground
Project (VUP), where WorleyParsons RSA is
providing engineering consulting services that
include detailed engineering, execution and
support in procurement and construction man-
agement. The VUP, which probably ranks as the
single biggest mining project currently under-
way in South Africa, includes the sinking of two
vertical shafts to depths of just over a kilometre.
Turning to the work at the Nchwaning
mines, Greyling says a relatively early achieve-
ment was the completion in September 2014 of
Nchwaning II shaft feed
conveyor drive and take-up
arrangements.