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Introduced into the South African
market by Kaytech, the Tensar
TW1 System was developed as an
alternative to traditional retaining wall
options and has been used extensively
in Europe and elsewhere internationally.
The system was recently used on a major
road upgrade contract in Ballito, one of the
first and largest local applications of the
system to date.
Project engineers, SMEC South Africa,
were involved in the detailed design of
the system and realised a number of cost
benefits on the project by using the Tensar
TW1 System.
The scope of works entailed the
widening of a two-lane, single carriageway
to a three-lane, dual carriageway in Ballito,
about 40 km north east of Durban. Due to
the site’s undulating topography, earth-re-
taining structures had to be built to bring the
extra lanes to level. The lane widening had
to be constructed within the road reserve to
eliminate encroachment into existing devel-
opments. To reach this objective, two near
vertical, Mechanically Stabilised Earth (MSE)
walls of 11 m and 5 m, covering a total length
of over 400 m and 2 000 m
2
, were proposed.
A key consideration in the design was
to optimise the use of lower quality fill
material, while simultaneously minimising
the amount of lateral support required in
cutting back and benching into the existing
roadway; i.e. the back excavation slope.
Limited space was available for the 11 m
high wall, which restricted the length of the
strips to 7 m. At the same time it would be
beneficial to the project if Berea sands could
be utilised. However, by using the lower
quality fill, strip lengths would need to be
increased, which implied either increased
cut or the use of a near vertical back excava-
tion slope requiring the use of shotcrete and
ground anchors or nails.
After a number of iterations, the final
design for the 11 m high wall comprised the
use of 7 m long strips, a granular backfill for
most of the height and 1 m thick granular
soil-raft foundation. No lateral support was
thus required and conventional benching
Kaytech SystemUsed in Major Ballito Road Upgrade
Project information
• Company entering: Kaytech
• Project start date: June 2013
• Project end date: September 2014
• Client: Kwadukuza Municipality
• Project team: Kaytech, SMEC and Afriscan
• Main contractor: Afriscan Construction
• Project manager: SMEC South Africa
• Project value: R8,5-million (walls and fills)
into the existing fill was utilised. For the
upper 3 m of the 11 m wall and for the 5 m
high wall, Berea sand was used throughout.
In utilising the new system a number
of challenges were experienced during
construction. These included: the setting
of the base block, which is key to achieving
the final face inclination of 86°, compac-
tion criteria, stormwater control, and the
use of labour inexperienced in building
these walls. However, these problems
were quickly resolved through close collab-
oration between the contractor, consultant
and supplier.
From the Environmental Assessment
it was noted that the removal of existing
indigenous trees within the road reserve
would result in a loss of biodiversity. This
however was unavoidable due to the nature
of development. Rehabilitation measures
had to include replanting the same species
of trees. Also during construction large
amounts of soil disturbances are expected.
Re-vegetation of all disturbed soil was insti-
tuted immediately after construction.
As another environmental advantage,
the TensarTech TW1 system (MSEW) is ideal
as an alternative to traditional retaining wall
options as the geogrid and geotextiles used
in its construction assist in reducing the
project carbon footprint, and at the same
time minimise the use of natural materials.