THE CONCRETE CULVERTS
are manufactured by Concrete Manufacturers Association
(CMA), member Aveng Manufacturing Infraset and designed by the company’s Technical
Marketing Manager, Coenraad Groenewald. These are some of the country’s largest culverts
thus far and could well be its biggest single culvert order ever. Weighing 12.8 tons each, they
are produced at Aveng Manufacturing Infraset’s Brakpan manufacturing facility.
International consulting engineering concern, DRA Mineral Projects, is responsible for the
engineering, project management and construction work on the entire project.
This is the first time that DRA has used precast concrete culverts for erecting coal stockpile tunnels.
Although steel and
in-situ
concrete were considered, DRA Project Engineer, Arthur Oosthuizen,
says recent durability and maintenance concerns with steel tunnels and time constraints with
in-situ
concrete construction prompted the decision to opt for precast concrete.
The culverts comprise solid steel-reinforced concrete and are designed to handle well in excess of
the maximum 20-ton loading they are likely to encounter at the Tweefontein buffer zones. Each
contains 600kg of reinforced steel and measures 3.5m (height) x 5.3m (width) x 1m (depth). The
walls are tapered, with a maximum thickness of 350mm at the top end, which narrows to 300mm
at the base of each foot.
The initial requirement was for a height of 4.7m, but this would have rendered the culverts too
large for transportation by road. To make up the required height, the foundations have been built
with elevated uprights measuring 500mm.
Given the culverts’ non-standard dimensions, six custom-made steel moulds are used for the
horizontal casting. Seven 200x200mm steel utility plates are cast into the inner sides of each
culvert, to be used as attachment points for channelling electrical cabling and conduit. Once cured,
the culverts are loaded horizontally onto low-bed trucks, each bearing two culverts.
Rather than using custom-made machinery to shift the culverts into the vertical plane on site,
Coenraad Groenewald adopted an innovative approach by using gravity, by attaching a steel beam
to the upper end. By lifting this end with a crane, the culvert gains its vertical elevation; it is then
raised and lowered into position on the foundation.
“We are under severe time constraints and are currently working a double shift, which means at
maximum output we can produce 12 units a day.We are also working on Saturdays to ensure that
the culverts are delivered on time,” concludes Coenraad.
Colossal concrete
culverts
Close on 800 giant precast concrete culverts, three-and-half
metres high and just over five metres wide, are being been
deployed in the construction of two buffer (stockpile) tunnels at
Glencore’s Tweefontein Optimisation Project near Witbank.
