Construction World May 2016

PROJECTS AND CONTRACTS

MINE ROAD construction

Fibertex South Africa has supplied high volumes of heavy grade nonwoven needle punched geotextiles to be used in ongoing road constructions at a major gold mine in Ghana’s Akyem mining region.

A major challenge was the formation of a durable road structure, with sufficient bearing capacity to withstand required loads, including dump trucks carrying in excess of 250 t of ore per trip.

This project involves continuing construction of an access road to the open-cast pit, where mining excavation is taking place. “A major challenge was the formation of a durable road structure, with sufficient bearing capacity to withstand required loads, including dump trucks carrying in excess of 250 t of ore per trip,” says Chris Powell, Fibertex South Africa – manufacturers of geosynthetic products. “Continuous heavy wear and regular rainfall in this region necessitated a robust road formation, with prolonged service life and minimal mainte- nance requirements.” Fibertex F750M Polypropylene nonwoven geotextile was introduced as a basal separator to prevent aggregate grade mixing, with no risk of contamination of the aggre- gate base. In road construction, migration of the various layers reduces the load bearing capacity of the road and must be prevented. The solution The Fibertex nonwoven geotextile’s porous structure prevents the migration of weak subsoils into the quality engineered fill and also inhibits the loss of quality aggregate The ‘tension membrane effect’ provides the required compaction of the road aggre- gates and thus increases the bearing capacity of the road to withstand continuous heavy traffic loads. Geotextiles, with excellent hydraulic filter properties, have sufficient permeability to allow free movement of water. This will provide long term stability of the > into the weak subgrade below. In this process the geotextile also provides stability to the base layers.

foundation layers and ensure an extended life of the new road. Another advantage of using geotextiles in this project is the significant reduction of fill material required during construction. Because of the lack of suitable construc- tion materials in remote African locations, construction aggregates often have to be transported, at a huge cost, over long distances. By reducing the amount of engi- neered fill required, the installation is simpli- fied and time and cost savings are achieved. Fibertex non-woven geotextiles are engineered to have high mechanical stability, not only for in-field performance, but also for possible damage that occurs during the installation process. Geotextile mechanical stability is achieved by having a high elongation and high tensile strength per weight, to resist failing under load. During construction, when sharp heavy rocks are dumped directly onto the geotex- tile, or when heavy construction traffic forces the geotextile into the subsoil, the geotextile will strain or elongate, while maintaining its mechanical integrity. Other critical durability features include the geotextile’s stability over a wide pH range (3-12) and its resistance to fungal attack and biodegradation – an inherent quality of the Polypropylene polymer the geotextile is produced from. In applications where the geotextile will be left exposed for prolonged periods, UV inhibitors are added as part of the polymer extrusion process to give long term UV stability. An extensive range of geotextiles is manu- factured at the Fibertex manufacturing facility

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in Hammarsdale, KwaZulu-Natal, according to stringent international quality, safety and environmental specifications. This involves line testing for a consistent high quality product and QC testing to ensure all nonwoven products meet every customer’s requirements. The local operation – which forms part of a global organisation, with its head office in Denmark – incorporates a combination of carding; needle punching and thermal bonding processes, using the latest tech- nology. All processes are automated and product quality is controlled by a central QA system. Concern for the environment is crit- ical at Fibertex and no chemical binders are used in the product or production process. Geosynthetic range The Fibertex geosynthetics range encom- passes nonwoven and woven geotextiles, gabions and mattresses, drainage pipes and fittings and erosion control and cellular confinement solutions. The company also supplies soil rein- forcing products, including geogrids and geocells, as well as geosynthetic clay liners as part of composite lining systems in modern landfills. Fibertex industrial nonwoven fabric products are manufactured for use in a diverse range of industries, including automotive, filtration, furniture and flooring applications.

CONSTRUCTION WORLD MAY 2016