The new Olivedale Retirement Village installed a block wall reinforced with a Kaytech geogrid instead of a retaining wall on site.
The new Olivedale Retirement Village, situated in Olivedale, Randburg, is situated on a very steep slope. The steep slope required the construction of stable platforms in order to create a solid foundation for the construction of the retirement units.
The contractor, Lonerock Construction, appointed Engineered Interlock Solutions as the sub-contractor and the project team, and together with TMW Consulting Engineers decided to change the original tender for a 90ᵒ reinforced concrete wall to a block wall reinforced with a Kaytech geogrid.
The dry stack wall, which was reinforced with Kaytech’s Miragrid GX 80/30, was not only an effective solution but it also cut costs for Central Developments Property Group, the developers of the Olivedale Retirement Village.
Miragrid GX geogrids are manufactured from high tenacity polyester (PET) yarns and knitted together to form a structured grid with a protective polymeric coating. The geogrids are particularly well-suited for the reinforcement of vertical or inclined soil walls with modular block or panel facings.
Miragrid GX 80/30 was placed at every second block lift of the wall with tie back lengths of 5,4 metres. One of the key benefits of Miragrid GX is that it enables effective interfacing with concrete block structures, thereby solving the problem of uneven and unstable blocks (which is a common feature with extruded geogrids).
Kaytech is able to supply the geogrids in custom strengths and sizes to fit the needs of various projects. Approximately 14 800m² of Miragrid GX 80/30 was installed at the retirement village site. The product’s performance has been independently verified and tested, and it provides long-term durability (it will last over 100 years) and low creep resistance.
Constructing a blanket drain on site
The 60m-long wall was constructed at an 85ᵒ angle and reached heights of up to 7,5m. A layer of Rockgrid PC 100/100 was installed on the second last tier of blocks to provide control against internal erosion as well as reinforcement.
To prevent the possible build-up of hydrostatic pressure behind the closed face Infrablock 350 Multiblend splitface blocks, a blanket drain was constructed. This blanket drain consists of a layer of bidim A2, covered with a 120mm layer of 19mm stone followed by a second layer of bidim A2. Outlets were provided at 3m centres.
Kaytech manufactures bidim (which is a nonwoven, continuous filament, needle-punched geotextile) from 100% recycled polyester in their ISO 9001:2008 accredited facility. Some of the benefits that bidim offers over man-made fibres include better modulus deformation, better plastic yield stability and higher breaking strength.
Bidim is flexible, which lends itself to easy installation. The mechanical process of needle-punching provides an appreciable thickness, high porosity, even under heavy loads, and a high drainage capacity in both the normal and transverse planes.
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