The Civil Engineering Contractor January 2019 | Page 19

ON SITE
currently active all over Africa and
particularly West Africa, serviced
through its branch office in Lagos.
Challenges of shallow rock
Nico Haas is CEO of Gauteng’s
second-largest piling company,
Gauteng Piling, a firm which has
16 large auger piling machines.
This positions it as one of the larger
piling companies, with most regional
companies having an average of
four to five. The national companies
typically have 25 to 30, explains Haas.
Having such a large variety of
equipment at its disposal has allowed
the company to embark on contracts
ranging from underpinning for
residential houses to massive housing
projects in Angola. Haas says Gauteng
Piling actively promotes the idea of
partnering, which means working
together with all the parties to a
contract, as a team. Oxglen Phase 2
is a prime example of this approach.
The gunite for the site’s wall is
placed while not quite dry, says Haas,
though with as little water as possible
mixed. The gunite is a mixture of
cement, sand, and water applied
through a pressure hose, producing
a dense, hard layer of concrete also
used in building for lining tunnels and
structural repairs. As it is sprayed on,
the water is added at the nozzle using
the same technique as they do for
swimming pools.
“It is a relatively straightforward
job, but it had the challenge of some
of the piles being founded on shallow
rock. Extra holes had to be drilled to
ensure piling was not on a ledge but
on rock. However, this was expected
and planned for,” says Haas. Gauteng
Piling had undertaken piling on both
the adjacent sites on behalf of Barrow,
“so we had a fair idea of what was
there,” he says.
Haas says it is a useful risk
mitigation technique to get the
same piling company and the same
geotechnical company to work on
adjoining sites. “It is very important
to do a geotechnical investigation
if you don’t know what is going on
in that area. There are lots of jobs
we tender on where there is not a
www.civilsonline.co.za
The single biggest challenge in piling is understanding the ground conditions.
CEC January 2019 | 17