The Civil Engineering Contractor May 2019 | Page 30

FEATURE: PILING AND LATERAL SUPPORT
The range of drill sizes for different-diameter piles.
(which is the only time the entire
plant shuts down), as well as 24-hour
work. We are piling in a vast area of
rock, boulders, and concrete (from
previous works) of what is atrocious
conditions because nobody knows
what’s under there. It’s an interesting
job in which we are employing a self-
drilling anchor technique (SDA). This
involves installing a small hollow bar
into a small hole which is percussion
drilled and grouted. It is this mini-
pile configuration that carries the
load of the structure above.”
Another option for piling is dynamic
compaction, which was not used on
this site, but which is also sometimes
employed when ground conditions
do not suit piling. Whittaker says this
option would normally be used only
on a large site. “It is not an exact art,
and there can be complications if it
is not done correctly. It is also time-
consuming.” It has, for instance, been
used on the CEOCO project, profiled in
this month’s On Site feature (page 12).
MegaPile company has also been
involved in a prestigious project
called Sandton Court in the heart of
Rivonia, which was interesting from
the viewpoint that it was surrounded
by developed adjacent properties and
therefore needed considerable piling
and lateral support to protect the
walls from caving in as the contractor
excavated down. The company is also
involved with developer Interprop
28 | CEC May 2019
on the piling and lateral support for
the Oxford Parks Development, on
Oxford Road, Rosebank, where there
are five mixed-use precincts being
established at the moment.
“We’ve also recently completed a
project called ‘Rockefeller’ on the
foreshore in Cape Town, having only
recently opened our branch in the
Mother City.”
Gauteng Piling has recently been
involved in the Atria project in
Waterfall: consisting of two office
buildings, Atria East and Atria West,
which when complete will comprise
approximately 7 000m² each, with
floor plates that will range between
1 300m² and 1 500m², a 180-bedroom
hotel, and 120 residential apartments.
Maas says their component of the
project consists of about 240 piles. “It
was interesting because the ground
had areas of shallow rock and we had
to drill into the very hard rock to
get the uplift capacity required for
two cores. We prefer to stick to our
knitting of augered piles, although we
also do various other types of piles.”
Franki Africa is well represented
on the continent, having recently
completed projects in Mauritius,
Angola, Ghana, Mozambique,
Tanzania, Uganda, Swaziland,
Botswana, and Zambia. One of
Franki’s project achievements of
late is the piling it undertook at the
Multisports Complex, Mauritius. This
involves the construction of a new
sports complex for the Indian Ocean
Games scheduled for July 2019 at
Côte d’Or, St Pierre, Mauritius, and
includes athletic training grounds and
track, a football pitch, an aquatic
centre, and a multipurpose gym
on behalf of Mauritius Multisports
Infrastructure Limited.
In an article on Franki’s website,
Mauritius country manager Yannis
Mongelard says that the tender, which
was launched in December 2017
with anticipated start in early 2018,
stipulated 96 days for the piling work.
“This was not possible for a host of
different reasons at that time,” he says.
“We submitted a solution which was
cheaper, allowed for an earlier start
and which could considerably cut
down on the length of the job under
normal circumstances. Moreover, it
enabled us to work with the plant we
had on the island at the time, which
contributed significantly to the cost
saving on the project.”
Mongelard adds that from the
original piling-only solution in the
tender, Franki further enhanced
efficiencies with a solution
comprising a mix of piling and
ground improvement. “The original
tender specs involved the installation
of more than 850 temporary cased
auger piles of various sizes drilled
to an average depth of 21m. Our
ultimate solution comprised ground
improvement in conjunction with a
mix of piling techniques optimised to
support each of the structures.”
He explains that piling and ground
improvement was required, following
geotechnical investigations that
found worse-than-expected ground
conditions. “Moreover, the required
bearing capacity of the backfilled
soils could not be achieved, so deep
foundations (piles) were opted for.”
While these solutions could have
cut down on production time, it
turned out that high rainfall and
the clayey platform made it almost
impossible to achieve the daily
minimum production from the start.
In addition, the platform works
could not proceed because the
www.civilsonline.co.za