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DECEMBER • 2016
Construction
WORLD
18
Civil Engineering Contractors
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The Majuba Silo Recovery Project was covered under Phase D –
‘Permanent Solution’. It involved the materials handling solution
for the final stage to be developed in accordance with the results
of the Silo 20 structural investigation process as well as the
determination of the current conditions of Silo 10 and Silo 30.
It was however expected that the plant configuration will return it
to its original state.
The project was carried out the Majuba Power Station Site and
ongoing operations of the Power Station would take precedence
over the construction work. The works included sectional
completion in order to ensure that the coal supply to the power
station was not disrupted during construction and commissioning
of the works.
The foundations, columns, transition slab, benching and 12 m
height of existing shell was kept intact. The external face of the
remaining existing concrete shell was cleaned (water power wash),
checked and shear connectors were epoxied where required.
About 1 m of the damaged top edge of the existing 350 thick shell
was demolished, leaving the rebar exposed for incorporation in
the re-cast benching. A 350 x 600 triangular edge beam had to be
cast to the top edge of the benching to accommodate the new
shell inside diameter.
MAJUBA COAL SILO 20 RECOVERY PROJECT
Majuba Power Station is in Mpumalanga situated
between Volksrust and Amersfoort. It comprises
six units, Unit 1-3 each capable of providing
657 MW and unit 4-6 each capable of providing
713 MW. Majuba Power Station has been in
operation since 1996 when the first unit was
put into commercial operation. It is planned to
operate until 2061.
Eight new 2 000 mm x 500 mm concrete columns to support
the new shell were positioned around the outside circum-
ference of the existing concrete and were excavated and
dowelled into the existing foundation and extended to just above
the existing openings.
The existing foundations, columns, transition slab, benching,
existing shell and concrete roof were kept intact. The external face
of the existing concrete shell (350 mm) was cleaned (water power
wash), checked and shear connectors epoxied in.
Six new 2 000 mm x 500 mm concrete columns and two
composite steel columns, to support the new shell, were
positioned around the circumference. The columns were
dowelled into the existing foundation and extended to just
above the existing openings.
Thereafter a new 50 mm x 20,7 m internal diameter stiffening
shell was constructed up to a height of 19 metres above the
existing benching line. The shell was bonded to the existing
shell by epoxied in shear connectors. A single formed slide
technique was used to construct both silo 10 and 30. These were
technically challenging as the slide started 12 m from NGL and
were completed/finished 11 m below the existing top of silo.
The formwork/sliding system during the assembly and stripping
sequences were carefully engineered.
The lift shaft is 5,39 x 5,2 m concrete box tower about 70 m
high. The remaining portion of the existing lift shaft stub below
ground level, was demolished while keeping the existing starter
bars intact. Some additional starter bars had to be epoxied into
the raft foundation. The 2 m raft foundation had to be excavated
to expose the west face to allow the wall to be fixed to and cast
against this face.
The collapse of the silo was a significant event with major
consequence on the power grid that caused serious power
shortages. The successful execution of the project restored the
operation of the power generation plant to full capacity. This
obviously assists with the current power shortages and the impact
it has on the economy.
Project information
• Company entering:
Stefanutti Stocks Civils
Rula Consortium
• Client: Eskom Majuba
Power Station
• Start date:
4 January 2016
• Project end date:
10 December 2016
• Main contractor:
Stefanutti Stocks
Civils Rula Consortium
• Project manager: Eskom
• Consulting engineer:
Hatch Goba
• Project value:
R114 032 465