Construction World January 2016

ROADS AND BRIDGES

REINFORCING Simon Vermooten Road

Base layerworks being constructed over the reinforcing RockGrid PC layer.

Additional lanes were created on Simon Vermoten Road.

> A decision by the City of Tshwane Municipality to double the size of the road included adding an extra lane to the bridge at the intersection of the N4. The multi-million rand contract was awarded to construction group, Liviero Civils with Aurecon as consulting engineers. The previous construction of the road embankment was found to consist of a G9 fill material whose high Plasticity Index (PI) explained the evidence of cracking in the layerworks. Having first considered the use of lime to reduce the PI of the fill material, engineers decided to contact Kaytech for possibly a better solution. Wouter van Zyl of Kaytech suggested the use of its unique RockGrid PC, the first composite reinforcing geotextile to bemanufactured in South Africa. Wherever soft soils with low bearing capacity are encountered, RockGrid PC will provide the most economical and time-saving solution. It consists of a nonwoven layer in conjunction with high tenacity, bi-axi- ally orientated, multifilament polyester yarns, the combination of which guarantees the unique characteristics of the product. The high tensile modulus of RockGrid PC provides excellent reinforcement characteristics and minimum creep deformation compared to polyethylene or polypro- pylene grids or woven fabrics. By mid 2014, 4 000 m 2 of RockGrid PC 100/100 had been installed along one section of the route, thereby providing a robust reinforcement layer upon which the new road could be constructed. Graded material was imported for construction of the layerworks above. The high tensile modulus of RockGrid PC provides excellent rein- forcement with minimal deformation, while its nonwoven component provides high resistance to installation stresses. Only RockGrid PC provides sufficient drainage capacity to drastically reduce flow paths in the reinforced soil. Due to this water transmissivity, RockGrid PC facili- tates the reduction of pore water pressure and improves shear charac- teristics, thereby increasing stability. This installation of RockGrid PC covered only a section of the full project which has been subjected to numerous delays including heavy rains and the subsequent decision to incorporate Tshwane’s Bus Rapid Transport (BRT) system. This necessitated the redrawing of plans to include future BRT stations on the median of the road as well as another extra lane on the bridge to accommodate the BRT system. Kaytech will continue supplying its RockGrid PC which, compared to the use of lime, has already saved a considerable amount of time and money. Once completed, the upgrade to Simon Vermooten Road will greatly reduce travelling time for the thousands of commuters working in the city.

Consultation with Kaytech’s Christiaan van Wyk significantly cut the costs on a huge road upgrade project in Pretoria East. Traffic congestion on Simon Vermooten Road, an important arterial route from Mamelodi and the eastern suburbs to the N4 Highway, had reached critical proportions.

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RockGrid PC was chosen over lime to mitigate the embankment's high PI.

CONSTRUCTION WORLD JANUARY 2016