The Civil Engineering Contractor May 2019 | Page 16

ON SITE: PROJECT 1
the poultry industry, but once the
boilers have been commissioned, the
husk will be used as biofuel for the
boilers. The boilers they’ve ordered
are configured to be able to burn husk
and coal to fire the boilers. The soya
facility is an upgrade of the business’s
current capacity (located in Delmas)
and re-establishing it on the Boksburg
site. The soya production facility
was designed from scratch using
the client’s technical and practical
knowledge and 40 years of exposure
and experience in the industry.
Trucks arrive directly from source
of the raw material (sunflower
seed or soya bean). Initial OH&S
checks are undertaken at the main
guardhouse, whereafter articulated
vehicles proceed to a seed sampling
station where samples are taken
and immediately analysed, giving
permission for trucks to proceed,
or rejected. A fully automated
weighbridge system will guide the
vehicles through the offloading and/
or loading process, right through to
obtaining the final waybill ticket.
Sunflower husks, soya meal, and
sunflower meal are transported on
overhead gantries via conveyors to
either the nine silos for meal storage
and distribution, or to another seven
silos for husk storage as fuel for the
boilers. Sunflower and soya crude oil
is pumped via the overhead gantries
to ten 12m-high tanks, each with a
capacity of 500 000ℓ. The oil, says
Maitre, either gets piped to the adjacent
business for manufacturing purposes
or delivered to customers using oil
tankers for the distribution. Overhead
gantries housing crude oil pipelines
and conveyors ensure transport of all
product around the site.
The meal silos are conical elevated
structures — the only way meal can
be preserved and shifted to conveyors
to be loaded onto trucks. “They are
quite a challenging construction
Steel erection to the new soya plant against the soya silos in the background.
14 | CEC May 2019
build,” says Maitre. The base is a
solid reinforced concrete (RC) raft
supported onto the dynamically
compacted in situ soils. This base in
turn supports the RC columns, above
which a 17.5-degree sloped RC slab
accommodate the loading channels.
This elevated slab also supports
the steel silo and a state-of-the-
art flooring system that has been
sourced and imported from abroad
to facilitate movement of the meal
within the silos.
A new office block will also be
built adjacent to the soya plant to
accommodate the employees required
for the expanded soya plant. There is
substantial open space in reserve for
future expansion.
Project challenges
One major challenge is coordinating
timelines: the seven 30m-high steel
seed silos are being manufactured
in Turkey (but branded a tongue-
soothing MySilo). They are
currently being erected; however,
they required storage on site until
completion of the civils work for
each silo. The foundation, circular
reinforced concrete retaining walls,
and complex fluted reinforced
concrete surface beds with extensive
aeration channels, bore with them
a construction complexity in itself.
“The silo top structures are a very
efficient steel corrugation assembly,
and it is amazing to think how much
concrete would have to be used
to achieve the same purpose,” says
Maitre.
The boilers are being imported
from the Philippines. “Everything’s on
the water, so to coordinate delivery
and construction has proven to be a
challenge,” he adds.
“The
foundations
were
problematic, as a second challenge.
Right from the onset, we knew we
had difficult geotechnical conditions.
The geology is loose-to-medium-
dense sands, which cannot support
conventional foundations. We had
two options: piling the whole site,
which would be quite costly (albeit
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