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CONSTRUCTION WORLD
JULY
2017
Franki Africa is part of the
Keller group, the largest
independent geotechnical
contractor in the world.
Pier 2 piles trimmed in preparation
for pile cap construction.
Piling for the bridge piers on the
new Tugela Ferry River Bridge.
90 tons and is ideally suited for the Tugela
Ferry piling solution.
“We owe a lot to the BG28 which has
enabled Franki to implement many cost-
efficient solutions to a wide range of clients
since it first arrived in this country from
Germany in 2012,” Pearce says.
Another time-saving solution used by
Franki was the construction of a movable
ramp to create the required 1 in 6 rake,
meaning that it is not necessary to modify
the platform earthworks for each pile. “With
all six pier piles raking in different directions
this represents a major cost and time saving
solution,” Pearce says.
Dealing with the unexpected
The necessary raised platform and variable
rock levels, resulted in suitable founding
rock only being encountered at depths of
over 25 m for some piles – 10 m deeper than
the average expected – but piling production
has still met expectations. “The BG28 has
comfortably dealt with deep boulder layers
and, as expected, the cluster drill has formed
sockets in vastly reduced time,” Pearce says.
It was not all plain sailing, however, and
one operational disadvantage has been that
the hard boulders and rock have caused
extreme wear on cutting teeth and bits,
which have required regular maintenance
and replacement.
Another disadvantage has been that when
forming the socket with the cluster drill,
the rock in which the socket is created
is reduced to small chips and dust. This
means that the rock quality is more difficult
to assess post-drilling and a thorough
geotechnical investigation is essential prior
to construction. “As with most geotechnical
works, the cost of a thorough geotechnical
investigation is easily recovered during
construction through design and
construction cost savings, for the ultimate
clien,” Pearce says.
Conclusion
With several lengthy work stoppages due
to flooding of the access causeway, the
piling is expected to be completed in mid-
July 2017.
Following on, the main contractor will
complete the abutments and bridge piers
and place the precast beams supporting
the new deck providing a safe, dual lane link
between the north and south banks of the
Tugela River and helping to uplift Tugela
Ferry and the entire surrounding area.