Challenges posed by clay soil and high water tables are overcome by Kaytech solutions.
When a drainage problem occurred during the construction of one of the residential properties in Meyersdal, one of the Gauteng province’s largest and most exclusive eco-estates situated in Alberton, south of Johannesburg, Kaytech solutions were used to address the challenges faced.
The clay soil conditions and high water table levels in Meyersdal caused the main construction and drainage problems.
To obtain the correct foundation level for a floor slab at this particular property, the contractor had to excavate to a depth of 3,5m, necessitating the construction of a retaining wall surrounding the house. As a preventative measure against the high water table, a 3m Kaytech Flo-Drain was installed on the upstream face of this wall.
Flo-Drain is a pre-manufactured composite subsoil drainage system comprising a Flownet drainage core wrapped in a bidim geotextile filter jacket. Flownet is a heavy-duty, extruded, HDPE drainage net, while bidim is a non-woven, needle-punched geotextile providing the optimum filtering performance in most soils. Compared to a conventional aggregate drain, Flo-Drain is cost-effective, lightweight, flexible and easy to install.
The homeowner also required a basement to be constructed which made it necessary to install a drainage layer beneath the concrete slab in order to prevent groundwater from seeping through the joints.
The specialist sub-contractor consulted with Winnie van der Merwe of Kaytech to design a solution for this problem. She suggested a blanket drainage system comprising (top down) Flownet HP500, S270 Kaytape and bidim A2 that would drain into a Megaflo 150 outlet. An HPDE plastic liner would be installed above the Flownet onto which the reinforced floor slab was cast.
Kaytape is a slit film, woven polypropylene tape geotextile, used as a high modulus separator in composite drains. Megaflo consists of a high-strength HDPE core completely wrapped in a bidim geotextile filter to act as both a collector drain and conduit pipe in subsoil drains. It is a cost-effective, easy–to-install solution to all subsoil drainage and its high crush resistance prevents buckling during installation.
This system was constructed by carefully placing Megaflo 150 into herringbone system of trenches. Since the soil conditions were not suitable to place the in-situ backfill directly against the bidim filter sock, the entire Megaflo system was covered with washed river sand to add filtration diameter to the drainage system. This was followed by the blanket drain of bidim A2, S270 Kaytape, DN3 Flownet and the HDPE plastic liner.
In total, 550m Megaflo and 550m² of each of the Flownet, Kaytape and bidim were used on this project. With Kaytech supplying on-site assistance and regular feedback, the specialist sub-contractor found the installation of these drainage systems to be simple, and was completely satisfied with the provided products.
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