The Civil Engineering Contractor October 2018 | 页面 21

ON SITE
The tight construction site abuts the
surrounding buildings.
Liviero Building, says: “The civils
component of the building [currently
under way at the time of interview]
is a relatively small portion of the
total cost, having but one basement
level. As there had been a pre-existing
basement — of approximately two
floors of retail and a basement, which
was demolished — no sewerage work
was required.”
Liviero Building is the main
contractor, with much of the work
subcontracted to civil construction
and building development company
Harrowgate. The latter specialises
in earthworks, road and township
infrastructure, substation civil
infrastructure and building works,
including warehouse construction,
and more.
The construction of the entire
building will, over the course of the
project, involve 11 000m 3 of concrete
and 1 600 tonnes of steel. At the time
of the site visit, the basement floor
had just been completed and work had
commenced on the basement surface
bed. Approximately half the ground
floor slabs as well as much of the
ground beams and basement columns
were already completed, including
the power caps and the foundation
brickwork. “We recently started
work on the ground floor columns
as well,” says Van Dalen. Liviero
Building will also be responsible for
the rest of the 17-floor building.
Challenges
The pre-existing basement structure
complicated the earthworks, explains
Hardus Marx, site quantity surveyor
for Liviero Building. “It made the
earthworks more difficult because we
did not have a clear idea of what was
below the ground. The only way to
see conditions below ground was to
dig down and see for ourselves. In the
event, we found a lot more concrete
than initially expected — including
bits of broken piles. Consequently,
we had to remove 8 000m 3 of material
more than had been budgeted.”
There were a number of other
surprises too. “There was a little bit
of asbestos found in the basement
structure, while beneath the ground
we unexpectedly found clay. An
entire process — including a legal
process with specialist permits —
was required to remove the asbestos
before our subcontractor Dracon
Demolitions could start with this
asbestos removal task. They in
turn subcontracted it to a specialist
firm. There was no rock found on
site, but the clay found in the soil
meant that conditions were far from
ideal when it came to compacting
the earth. “We had to drive in 366
precast piles, and poor soil conditions
meant that we had to import close to
1 200m 3 of G7 aggregate alone, to
create a suitable foundation for piles,
in addition to an amount of dump rock
to make different layers, followed
by the geotechnical membrane,”
CEC October 2018 - 19