Construction World October 2022

CIVIL ENGINEERING

Fibertex manufactures geosynthetic sand containers (GSCs) which are used in the construction of efficient protection structures for coastal protection, erosion control, dune revetments and slope stabilisation, as well as for emergency protection in floods. CARE FOR OUR COASTLINES

“A s coastal erosion becomes more prevalent, due to rising sea levels and changes in global weather patterns, it has become increasingly important to have well-engineered, durable and easily manageable coastal protection structures in place,” says Burger Fourie, Technical Sales Engineer at Fibertex SA. “Although using large sandbags as structural components of revetments is not new in environmental protection, Fibertex has made a substantial investment to design and manufacture a robust but soft GSC system, as an alternative to conventional rigid revetment structures. These robust GSCs are a l ightweight and workable geosynthetic substitute for traditional revetment systems util ising rock and even seawalls using concrete and reinforcing steel . “The function of a GSC 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 unl ike hard concrete structures, which predominantly protect by means of wave energy reflection, which could most l ikely have a negative long-term impact on adjacent structures. “Fibertex FiberRock GSCs were used for coastal rehabil itation at Umdloti beach in KwaZulu-Natal , over five years ago. The robust structure is still sound and highly effective in protecting the coastl ine.” GSCs consist of a strong porous base fabric, which 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 – l ike sand – while allowing the free passage of water. Fibertex AVL geotextile sand containers, which are manufactured from highly UV stabil ised virgin Polypropylene (PP) fibres, can withstand the effects of repeated wave attacks in harsh coastal environments and are the perfect soft solution to beach rehabil itation and coastal protection. Geotextiles used in the manufacture

of GSCs are required to withstand the effects of different environmental conditions from the geotextiles used for conventional separation, filtration, drainage and protection. The Fibertex team has given particular attention to critical factors in the development of this system, including abrasion, perforation, puncture and UV resistance, tensile strength and elongation, as well as permeabil ity and drainage. GSC material selection is critical to the long-term stabil ity of the entire structure. In the case of coastal protection appl ications, 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 delaminate under the harsh flow conditions expected from wave action. Fibertex has selected virgin 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. Other important properties for appropriate product selection include the design of the revetment structure, where environmental influences such as wave velocity, wave ampl itude, wave period and wave direction need to be taken into account. Size selection of GSCs for each appl ication is also critical . Smaller GSCs might be sufficient for less harsh conditions, but direct wave attacks often require a larger, more stable GSCs. The correct installation procedure and optimal fill ing and closure of GSCs prevent free movement of the bag, to ensure the long-term stabil ity of the structure.

26 CONSTRUCTION WORLD OCTOBER 2022