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CONSTRUCTION WORLD
JULY
2017
20
and subsequent further consultation after
our appointment, crucially meant that the
works started towards the beginning of
the wet season rather than, as had been
expected, at the beginning of the dry
season,” Pearce says.
This turned out to be one of the central
challenges of the project. “The timing of the
commencement of the works has caused
major access problems for main contractor,
Group Five, which has had to contend with
the mighty Tugela River regularly flooding
the access causeway during the wet season
– even during the current ‘drought’ in South
Africa,” says Pearce. “The access causeway
has been washed away several times with
equipment having to be moved off position
each time in anticipation. Fortunately,
there have been no injuries and no major
equipment has been lost because of these
precautionary measures.”
Franki’s scope of work includes the
installation of 48 no. 1 100 mm diameter
permanently cased oscillator piles. The
bridge deck is approximately 165 m long
and piles are required to support both the
north and south abutment and all 5 no.
intermediate piers with 6 no. piles per pier
raked at 1 in 6 and 6 no. vertical and 3 no.
raked piles per abutment.
The geotechnical data available indicated
typical river bed conditions with gravels,
sands and boulders up to 1,5 m in diameter
in layers above soft to medium rock
overlying hard to very hard rock. Fractures
in the rock resulted in the tender design
requiring 1,4 m rock sockets and dowelling
into the rock below every pile.
“Historically, river bridge piles requiring
sockets are slow to construct using driven
or screwed-in casings and ‘smash and grab’
techniques to form piles and sockets in
rock. The slow pace not only increases costs
but also increases the risks associated with
working in a river. We therefore opted for
oscillating casings down to rock level and
then using a cluster drill – a multi-headed
percussion hammer – for the rock drilling.
This solution has reduced construction time
by over 50%,” Pearce says.
He adds that the increased performance
of the cluster drill has enabled Franki to use
a longer socket length in lieu of the dowels,
saving further time and cost.
Both the oscillator and cluster drill are
mounted on Franki’s Bauer BG28 piling rig,
which has an operating weight of about
reinforced concrete bridge adjacent to the
existing steel structure. “This was a good
solution,” says Paul Pearce Franki Africa
KZN branch manager, “as it meant that
use of the existing bridge has not been
interrupted during construction.”
Pearce says that the Tugela Ferry area
has historically been a political hot-spot and,
as a result, the award of the main contract
was a lengthy process which involved
extensive consultation with all the relevant
local parties on their involvement in the
project. Ultimately, in June 2016, Franki was
appointed specialist subcontractor for the
piling works for the new bridge.
“The prolonged award of the contract
COVER STORY
FRANKI’S INNOVATIVE SOLUTIONS
help to bridge KZN community
Installation of raked pile temporary
casing through gravel, sand and
boulder layers.
People struggle to make a living in Tugela
Ferry and the harsh conditions were, for
many years, exacerbated by the town being
split by the Tugela River and connected only
by an inadequate single-lane bridge, the
Tugela Ferry Bridge, which has significantly
slowed the local economy by hampering
vehicular movement and has been a threat
to the lives of the multitude of pedestrians
that have had to share the bridge with cars,
tractors, bakkies, trucks and more.
Franki’s geotechnical solution
The KZN Department of Transport therefore
embarked on a project to widen the bridge
to two lanes by constructing a new,
The tiny town known as Tugela Ferry (named after the ferry that used to
connect the two halves of the town) in the local Municipality of Msinga,
part of the Umzinyathi District Municipality in central KwaZulu-Natal is
part of one of South Africa’s most impoverished areas.