on the existing wall. This ensured that the wall did not
fail due to imposed loads during the construction phase.
As a precaution all crane-based activities were situated
over 10 m from the quay wall.
To install the foundation piles the specification ad-
vised the use of impact hammers instead of vibratory
hammers, as the latter are known to have the potential
to induce vibration into the surrounding ground due to
their high frequency.
This vibration could liquefy the soil in a localised area
around the toe of the existing wall, which would reduce
the shear properties of the sub soil, most likely causing
the toe of the existing sheet pile wall to rotate, inducing
a serious failure.
To carry out the piling operation, the contractors
used two BSP hydraulic impact hammers. First a CG240,
with a 16 t dropweight, suspended from a Kobelco 180
t crawler crane and mounted on a 40 m x 15 m floating
barge, drove the 27 t king piles. Then a suspended CX85
with a 7 t dropweight was used to drive the sheet piles
and form the combination wall.
Prior to installing the piles, BSP carried out an im-
portant modification to the CG240 hammer. This in-
volved having legs fitted rather than a pile sleeve which
reduced the overall weight and also enabled the ham-
mer to drive the king piles while avoiding any clash with
the pile template which had to be kept in place until
driving was complete.
Geotechnical investigations allowed the SSA JV to
size the correct hammers for the project. During pile
driving the soil conditions along the quay wall were no
problem for the BSP hammers. Pile-driving durations in
excess of two hours previously encountered on Berth
12 were substantially reduced through the use of these
more powerful and reliable impact hammers.
Steel piles used for the combination wall included
double I section HZ 1180M piles (king piles) to form the
structural elements, and AZ 18-700 sheet piles acting
as filler sections amounted to some 10,550 tonnes. A
seven-bay pile guide frame was used to ensure the piles
were kept within their vertical and horizontal alignment
tolerances without twisting.
Because of logistical difficulties and space restrictions
the 27 m long king piles were located on a designated
area within the harbour complex where they were pro-
filed with a curved cutting edge to aid installation. The
402 anchor piles 33m long underwent additional prepa-
rations for the HP grout system.
Design consultant Railway and Civil Engineering
Consultants (RCE), the design consultant for project
manager Transnet Capital Projects, proposed that the
Müller Verpress Pile (MV-Pile or HP) system was em-
ployed for anchoring the combination wall, as an alter-
native to the traditional dead-man anchor solution. This
is the first time the system has been used on a construc-
tion project in South Africa.
The system makes use of H-section bearing piles
supplied with thickened flanges. The piles are usually
driven at 45 degrees to the combination wall through
the centre of the king pile to which it is later pinned.
While the pile is being driven to level, grout is pumped
out near the toe of the pile at 10 bar. The grout acts as
lubricant during driving, and once set, it bonds to the
steel pile and the surrounding substrate, increasing the
frictional resistance of the anchor as well as protecting
it from the adverse effects of corrosion.
The success of HP piling was measured through the
results of the test piles, which passed the stringent test-
ing and specification requirements set forth in the
contract and was an important aspect of the project that
the Stefanutti Stocks Axsys JV prides itself on accom-
•BSP Foundations International
We thank Eswee Kruger, site planner on the Maydon Wharf project,
for his photographs, and Tim Milner, consultant Bid Manager for
Stefanutti Stocks Marine for the use of his photographs and the text
in this article.
Contractors World International
Contractors World International Vol 7 No 4