Construction World September 2018

GEOTECHNICAL ENGINEERING

“A geing infrastructure, large waves and a narrow beach width, have contributed to the urgent need for upgrading loffelstein and gabion walls at Umdloti beach, to ensure greater environmen- tal protection,” explains Jeremy Wayne Muthusamy, key accounts manager, Fibertex SA. “The initial phase of this rehabilitation project – where Fibertex FiberRock GSC-Bags were used as a temporary measure for protection during the repair and replacement of the loffelstein wall - was completed in the first quarter of 2017. “In the final phase of rehabilitation, FiberRock 250V geo- containers have been used by Leomat Construction Durban, as a permanent revetment structure. Fibertex geotextile sand containers, which are manufactured locally from highly UV stabilised virgin Poly- propylene (PP) fibres, are able to withstand the effects of repeated wave attacks in harsh coastal environments and are the perfect soft solution to beach rehabilitation and coastal protection. “Fibertex GSC bags are a lightweight, durable and workable geosynthetic substitute for traditional revetment systems that utilise COASTAL REHABILITATION Fibertex FiberRock geosynthetic sand containers (GSC bags) have been used for further coastal rehabilitation at Umdloti beach, just north of Durban, KwaZulu-Natal.

rock and seawalls using concrete and reinforcing steel. FiberRock, which has a neutral, sandy colour, looks natural in a coastal environ- ment and is vandal resistant. “This robust structure encompasses a double row of geotextile sand bags, tied together. An advantage of this system over conven- tional methods is this structure is easily removed if necessary. GSC bags are filled with beach sand, with no need to import other filler materials to site. “A function of these GSC bags is to allow the free passage of water through the porous structure of the fabric and into the sand it carries, to absorb wave energy, while retaining the sand fill in the bag. This is unlike hard concrete structures, which predominantly protect by means of wave energy reflection, which could most likely have a negative long term impact on adjacent structures. “A challenge of this project, which was completed in March 2018, was having to work safely between tides and to protect the road from large wave events during construction, temporary sheet piles were installed.” The Fibertex team has given particular attention to critical factors in the development of this revetment system, including abrasion, perforation, puncture and UV resistance, as well as tensile strength, elongation, permeability and drainage. The strong porous base fabric of GSC bags is mechanically needle-punched together with a coarse anti-abrasion and vandal resistant (AVL) cover layer. This robust fabric combination offers a flexible structure that is able to retain a course fill medium – in this case beach sand – while allowing the free passage of water. GSC material selection is critical to the long term stability of the entire structure. In the case of coastal protection applications, where high energy bi-directional flow conditions are encountered, needle-punched staple fibre (SF) geotextiles are preferred. They have proven to be durable and the staple fibre geotextiles do not delami- nate under the harsh flow conditions expected from wave action. Fibertex has selected Polypropylene fibre, with excellent frictional and low density characteristics, as the basis for manufacturing its GSC fabrics. Polypropylene has better performance to weight ratio than other more dense polymers, such as Polyester. Although Polyester is a strong, durable polymer, Polypropylene is preferred globally in the manufacture of heavy grade/voluminous GSC fabrics. Fibertex geosynthetic sand containers (GSC bags) are also used in the construction of efficient protection structures for erosion control, dune revetments and slope protection, as well as for emer- gency protection in floods. 

Fibertex FiberRock 250V geosynthetic sand containers (GSC bags) have been used by Leomat Construction Durban, for further coastal rehabilitation at Umdloti beach, just north of Durban, KwaZulu-Natal.

FiberRock GSC bags, which are a lightweight, durable and workable geosynthetic substitute for traditional revetment systems, are locally manufactured from highly UV stabilised virgin Polypropylene (PP) fibres.

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CONSTRUCTION WORLD SEPTEMBER 2018