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Massive retaining wall project at FNB-Wesbank development

Written By Vero Pents on May 1, 2012 | 22:35

This 70 m x 7 m high retaining wall, built with INFRASET Terrace Blocks, supports a fire escape and is situated on the northern side of the FNB-Wesbank development in Fairland, Johannesburg

The Wesbank administrative centre in fairland, Johannesburg, is 
a development which has  generated considerable interest among
construction professionals and members ofthe public alike, owing
primarily to some highly innovative architecture used in its design by
Kim fairbairn of continuum Architects (Pty) Ltd.having been 
built on a site with a marked and varied slope, it is a development
which required extensive retaining wall support.A total of eight 
retaining walls were  built, some of which reached heights of 
7,5 metres. These cover an area of some 3 000 m2 and used close 
on 30 000 concrete retaining blocks (crBs) in their construction. crB 
walls are more cost-effective than conventional reinforced concrete 
walls and are considerably more attractive, facilitating as they do varying 
shapes and contours, as well as the growth of plants in the soil-filled blocks




All the walls were built by Kalode construction using 
infrASEt’s terrace Block retaining system, the one exception 
being an internal wall in the Basement 3, which was built 
using concor technicrete’s Envirowall block system. This wall 
comprised a geogrid-reinforced fill structure built at 85ยบ – 
the Envirowall block is best suited to this type of application.
Anyone visiting the site for the first time will immediately 
be confronted by a retaining wall at the Wilson Street entrance. 
Although not part of the fnB-Wesbank development per se, it 
was also constructed by Kalode construction on behalf of Brian 
Wescott construction. completed in 2006, the wall was built on 
the southern slope of the feeder road which serves both the 
fnBWesbank development and Worldwear Shopping centre adjacent 
to the fnB development. A pure gravity structure, the wall is 
60 metres end-to-end and reaches three metres at its highest point.
further evidence that retaining walls play a crucial role at 
this site becomes apparent at the gatehouse where 5 000 crBs 
were used to create an attractive 80 metre wall. once plants and 
flowers are established on this section of wall it will form an 
extremely attractive feature. The wall itself entailed a standard
design and installation. it rests on a concrete strip footing 
200 mm deep by 600 mm wide, tops 4,5 metres at its apex, and 
for the most part, slopes at an angle of 70°. Blasting was necessary
on parts of this section and the exposed rock face was covered with
crB blocks. one of the more challenging crB projects at the fnB site 
was a wall built to support a fire escape on the north-western 
side of the development. Seventy metres long and seven metres 
high, it was built at an angle of 70°. The fill in this wall is well 
compacted and reinforced with high strength polyester geogrids 
supplied by Kaytech . The fire escape sits directly on the 
structural fills and applies loadings on these fills of 150 kPa.
The wall built with concor’s Envirowall blocks is a vertical 
structure situated in the basement, which houses the building’s 
fire fighting equipment. Approximately 14 000 blocks were 
used on this wall and Kalode were responsible for all the fills 
and the stabilising. 

This wall was offered as an alternative to the originally 
proposed retaining wall as it was much more cost effective, 
by approximately 40%. Just on 100 metres long and reaching 
a height of 6,8 metres, the top half of the structure was 

A 140 m x 7,5 m retaining wall built with INFRASET Terrace Blocks on the southern side of the FNB-Wesbank development in Fairland, Johannesburg

reinforced with tensioned polyester geogrids which extend 
into the backfill. The bottom 2,5 metre section of the wall is 
constructed with a 5% cement-stabilised fill reinforced with 
tensioned polyester grids.  
Kalode construction managing director, Jan Pienaar, says 
Envirowall blocks were used on this wall as they are ideal for 
vertical structures that are heavily loaded. The bottom two metre 
section of the wall is cement-stabilised and soil-reinforced with 
stretched geogrids supplied by Kaytech. The top 4,5 metres is a 
conventional stretched soil      reinforced structure with the blocks 
acting more as a facing than a structural element. 
on the south-eastern and south-western section of the building a 
sunken wall 6,5 metres high and 93 metres long was built at a slope
of 70°. A composite wall, it was constructed with a double skin up to 
a height of four metres and a standard geogrid reinforced fill was 
used above that to maintain the weight.  
Another wall section, the south-western pod, was built around a staircase.
it is also a composite structure in which cement-stabilised soils and
geogrids, as well as plain geogridreinforcedfills and terraced stepbacks 
were used to accommodate the staircase landings and to break the stark
lines of a high crB wall situated in confined surroundings.it is 125 metres 
long, varies between three and eight metres in height, and has a 70° slope.
All structures were built with adequate subsoil drainage consisting of 
clean stone wrapped in horizontally-laid Kaytape A2. Wick drains 250 mm 
wide were laid on the face of the exposed embankment and these act 
as sub-soil cut-off and collector drains.

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