A massive amount of groundwater was posing a serious hazard to the foundations and walls of a home under construction in a housing development in The Willows in Lynnwood, Pretoria. The house is being constructed on a very steep gradient created by a cutting in the Magaliesberg Mountains.
To provide effective subsoil drainage, the on-site engineer proposed Kaytech’s FloDrain, bidim and Kaypipe geopipe.

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 commenced the project in November 2016.

Intercepting groundwater
FloDrain is an easily installed, prefabricated geocomposite drainage system supplied in lightweight, flexible 30m rolls pre-wrapped in a geotextile filter jacket of Kaytech’s renowned bidim. The system intercepts groundwater seepage and effectively lowers the water table.

It is an economical and practical method that can be used in a wide variety of applications, such as subsoil drainage for roadsides, sports fields and retaining walls.

Supplied in various grades, bidim is a continuous filament, nonwoven, needle-punched geotextile manufactured from 100% recycled polyester. The needle-punching process imparts several advantages including appreciable thickness, high porosity and a high through-flow 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 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.

High infiltration rate
Kaypipe geopipe’s 70% perforated surface area provides the highest infiltration rate compared to any other drainage pipe, thereby allowing for smaller diameter Kaypipe geopipes to be used. Manufactured from HDPE, it is lightweight, flexible and therefore easy to handle.

Although Kaypipe geopipe can tolerate extremely high stresses and does not become brittle, even in low temperatures, it was proposed that a conventional drain should 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, 210m each of FloDrain and Kaypipe geopipe had been installed as well as 207m² 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 success.

Kaytech
Tel: 031 717 2300
Website: www.kaytech.co.za

Captions Main Image:
The FloDrain covers the entire external wall to allow for sufficient drainage.