After assessing several different products to solve a stabilisation and drainage problem on the R28, a provincial route connecting Krugersdorp and Vereeniging in Gauteng, Calliper Consulting Engineers determined that Kaytech’s Rock-Grid PC would provide the optimum solution.
With rehabilitation underway along this Westonaria section of the R28, it was discovered that a low point of the road traversing a stream would require robust reinforcement and drainage to prevent recurrence of base layer failure and potholes caused by groundwater pressure. Besides RockGrid PC, specified for reinforcement, Kaytech’s world renowned bidim geotextile was specified as a filter for the subsoil drains.
RockGrid PC is the first composite, reinforcing geotextile to be manufactured in South Africa. The combination of a nonwoven layer in conjunction with high tenacity, bi-axially orientated, multi-filament polyester yarns, guarantees its unique characteristics; the nonwoven geotextile component offers optimum hydraulic characteristics and high resistance to installation stresses, while its high tensile modulus provides excellent reinforcement characteristics and minimum deformation. RockGrid PC provides sufficient drainage capacity to drastically reduce flowpaths in the rein-forced soil and, compared to polyethylene grids, polypropylene grids or woven fabrics, it demonstrates an extremely low creep tendency.
Chavani Construction was awarded the contract for the project which culminated in the installation of 8 000 m2 of RockGrid PC 50/50, as reinforcement between the in-situ sub-grade and the new pavement layers as well as 1 760 m2 of bidim A2 as filter for the subsoil drains, over the low lying section of road.
Manufactured from 100% recycled polyester, bidim is a continuous filament, nonwoven, needlepunched geotextile used worldwide in a variety of applications. The needlepunching process imparts several advantages including appreciable thickness, high porosity and a high drainage capacity in both the transverse and normal to the plane.
As a reinforced separation layer RockGrid PC 50/50 was simply installed directly over the saturated sub-grade, thereby preventing contamination of the selected materials above and providing improved bearing capacity. Experience has shown less fill material is required when using RockGrid PC 50/50 as a reinforced separation layer.
In addition to RockGrid PC and bidim, 804 metres of Kaytech’s robust FloPipe 110 mm were installed in the roadside subsoil drain which was designed to collect and direct groundwater flow into the nearby stream. Manufactured from the highest quality HDPE available, FloPipe is optimally slotted for maximum infiltration with minimal blockage. The twin-wall sandwich design provides strength and flexibility while the smooth inner wall ensures high flow velocity and the corrugated outer wall is able to withstand substantial confining pressure.
Although the final result of this project could not be assessed due to the remainder of the R28 being under construction, Kaytech can confidently assure the Gauteng Department of Roads and Transport that the combination of these high performance products will provide superior subgrade stabilisation and roadside drainage.
For more information on Kaytech products and systems, visit www.kaytech.co.za