The Civil Engineering Contractor August 2018 | Page 27

TECHNOLOGY
will be confined to Lesotho with the
objective of radically increasing water
flow through the transfer tunnel by
constructing a new dam in the Lesotho
water catchment.
Unpredictable occurrences on
site, says Jackson, consist either of
geotechnical reports sometimes
being wrong or not done, resulting
in hard rock being unexpectedly
found — and theft. Jackson fondly
recalls his toughest project, where
he was required to prove the worth
of the Brokk equipment his business
sells: “The client would only pay for
the equipment once it was proven
successful on site. It was a new
concept and a new technique to South
Africa at the time, and he would only
pay once the machine’s capabilities
were proven on site over two weeks.
His scepticism was because their
first-choice e quipment had failed to
meet demanding specifications. The
efficiency of our machine is now well
known — but it was nerve-wracking
that first time.”
viable such projects that previously
might have been too complicated and
difficult to be attempted.
Though, according to Gautrain's
Van der Merwe, tunnel construction
can be 100 times the cost of surface
construction, Ferreira says this is
nowhere near the case when building
basements. “It is more expensive, but
it is not like tunnelling. Once the
lateral support has been completed,
we are effectively just changing the
working platform level.” He says a
lot of the work around the Gautrain
project — which Franki Africa was
involved in with building stations and
parking areas in Rosebank, Sandton,
and Hatfield — is normal construction
work involving lateral support.
Three challenges
Ferreira lists three key challenges
surrounding traditional underground
construction:
• With a lot of civils work taking
place in highly built-up areas such
as Sandton, hitting underground
services is one of the major risks.
“When you’re inserting piles and
anchors, service lines such as
electricity, water, and fibre optic
cables have to be avoided in such a
Technology has improved to the extent
that projects involving the underground
component of city buildings can be
designed more expansively than even
a decade ago, explains Victor Ferreira,
group business development manager
at Franki Africa. The company is the
local subsidiary of Keller, one of the
biggest geotechnical contractors in the
world, and from which the company
gets access to the best technology and
support in the world, he says.
Fifteen years ago, we wouldn’t have
thought of excavating basements as far
down as 30m. Advanced technology
enables us to go deeper underground
than was previously possible, using
bigger anchors and piles and better
analysis methods.” It also makes
World class
With a TBM, the entire process has to be automated or a bottleneck occurs.