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CONSTRUCTION WORLD
AUGUST
2017
44
CEMENT & CONCRETE TECHNOLOGY
The site, at The Willows in Lynnwood,
Pretoria, was constructed on a very steep
gradient created by a cutting in one of
the Magaliesberg Mountains. Since the
resulting groundwater was posing a serious
hazard to the foundations and walls of
the home under construction, the on-site
engineer proposed using Kaytech’s FloDrain,
bidim and Kaypipe geopipe to provide
effective subsoil drainage.
The solution involved applying a torch-on
waterproofing system to the subterranean
walls followed by a protection layer of
polystyrene panels. The FloDrain fin
component was then installed vertically
against the outside of the wall and
connected to a conventional bidim A2 filter
geotextile wrapped drain comprising a
M100 Kaypipe geopipe collector encased
in stone aggregate. Impro, contracted to
install the Kaytech subsoil drainage system,
commenced the project in November 2016.
FloDrain is an easily installed prefab-
ricated geocomposite drainage system
supplied in lightweight, flexible 30 metre
rolls pre-wrapped in a geotextile filter
jacket of Kaytech’s renowned bidim. The
system intercepts groundwater seepage
and effectively lowers the water table in a
wide variety of applications, such as subsoil
drainage for roadsides, sportsfields and
retaining walls. FloDrain is an economical
and practical method that significantly
reduces the costs of transportation, labour
and materials.
Supplied in various grades, bidim
is a continuous filament, nonwoven,
needlepunched geotextile manufactured
from 100% recycled polyester. The
needlepunching process imparts several
advantages including appreciable
thickness, high porosity and a high
throughflow capacity both normal and
transverse to the plane to fulfil the drainage
function. Bidim also performs other
functions when incorporated in subsoil
drainage, namely that of filtration and
separation. Fine soil particles migrating
under hydrostatic pressure are prevented
from entering the drain while water passes
DRAINAGE AT THE WILLOWS
A private home in a housing development threatened by a massive
amount of groundwater has recently been saved by an innovative and
highly economical Kaytech drainage system.
through, thus lowering the phreatic surface
in the surrounding soil.
To cope with the excessive amount of
groundwater seepage at different levels
across the cut face, the contractor installed
the FloDrain system at varying heights.
Specially designed Kaypipe geopipe is
the most practical solution for all drainage
problems. The 70% perforated surface area
of Kaypipe geopipe provides the highest
infiltration rate compared to any other
drainage pipe, thereby allowing for smaller
diameter Kaypipe geopipes to be used.
Manufactured from HDPE, Kaypipe geopipe
is lightweight and flexible and much easier
to handle than other drainage pipes.
Although Kaypipe geopipe can tolerate
extremely high stresses and does not
become brittle even in low temperatures, it
was proposed that a conventional drain be
installed at the base of the FloDrain, as the
Kaypipe geopipe could possibly be crushed
by the sheer amount of compacted fill to be
placed above it.
By completion of the project, 210 metres
each of FloDrain and Kaypipe geopipe had
been installed as well as 207 m2 of bidim
A2. When heavy rains were experienced
soon afterwards, with no detection of water
or dampness in either the foundations or
walls of the house, the project was deemed
a great success.
Flo-Drain covers the entire external wall to allow for sufficient drainage.