The Civil Engineering Contractor July 2019 | Page 35

The Liebherr 855, Liebherr 8070 and NCK Ajax Franki and pre-drilling rigs ready to commence with the piling contract for Sappi at its
Saiccor mill in Umkomaas
depths of 24m — an all-time record for the company — but
installation would also have to be performed at very shallow
depths of between of 5‒8m.
Byrne says it is not only this significant variation in depth
that was challenging, but also how quickly the founding
depth changed. “Over large parts of the site the founding
depth would vary by as much as 15m. This was perhaps the
single most challenging condition of the site and necessitated
very careful site planning and fast and constant evaluation
of the deeper areas of founding to ensure that the heavy
equipment could be continuously utilised.”
In a nutshell, Franki has had to deal with some of the
shallowest conditions it has ever dealt with, juxtaposed
with the deepest it has ever had to deal with, and the Franki
pile proved to be exactly the right solution. “This is mainly
because the Franki pile accommodates a wide variety of
difficult founding conditions and provides remarkable
settlement performance and load capacity,” explains Byrne.
Not the end of the Franki pile’s
advantages
One of the stipulations was that the piles had to resist uplift
forces. Franki’s Jonathan Day, who was instrumental in
the final design of the job, says any other pile such as, for
example, auger or CFA piles, would have been a much more
expensive and complicated solution due to these piles having
to be socketed into the bedrock. “The Franki pile’s large base
is the best solution in this regard mainly because it can be
founded on the rock surface while providing superior uplift
capacity,” he says.
Two more site conditions reinforced the choice of Franki
piles. First, there were boulders at localised portions of the
site at various depths and Franki piles are able to penetrate
the boulder horizon. Second, across the majority of the
site there are very soft, silty clays and the Franki piles are
ideal for driving through such material with the Franki pile
www.civilsonline.co.za
casing preventing collapse of the material and ensuring the
integrity of the pile shaft concrete.
A total of six piling rigs are being used on the job. These
include three standard Franki crawler piling rigs for the
shallower piles, an Ajax 55t crane with leader for the piles to
about 17m, a 70-ton Liebherr for the 18‒20m piles and the
recently introduced large Liebherr crane ( 90t) for the deeper
piles including Franki’s deepest, history-making piles of 24m.
Day says that the timing has been one of the important
challenges of the job. “Our client required certain key milestones
to be achieved and set stringent targets for each section of the
job. In this regard I am pleased to say that we have completed the
first sections on time and on budget. The excellent relationship
between ourselves and our client Sappi has been fundamental to
the success of the project thus far,” he concluded.
Meanwhile Errol Braithwaite, Franki MD, says that he
is proud of the quality projects that Franki is involved in,
especially in the currently challenging economic climate.
“I am very confident about the future. Over the years,
Franki has been privileged to employ some of the foremost
geotechnical engineers and constructors on the continent.
Many of these have been internationally recognised as
experts in their field.
We are now seeing a new generation of wonderful young
talent emerging which is highly skilled, highly motivated and
more representative of our diverse nation than ever before.
The company is embracing new geotechnical techniques
and through our parent company, Keller — the largest
independent geotechnical construction company in the world
— we have access to the quality of international expertise
and technologies that will ensure that Franki remains the
leader in geotechnical expertise and the employer of choice
in this field throughout Africa.
He adds that perhaps Franki’s most important attribute is
the quality of customers, like Sappi, that it has served over
the years. “This has been a privilege of the highest order and
I am pleased to be able to express our gratitude to them out
loud and in public.” nn
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