eosynthetic products manufacturer and supplier Fibertex South Africa is providing an ongoing supply of its geosynthetic products for use in the construction of State-owned power utility Eskom’s Pinotage substation, in the Western Cape.
This new large electrical substation is located in Faure, near Somerset West. The supply by Fibertex began in November 2016.
Fibertex geosynthetics divisional director Paul Baxter informs Engineering News that Fibertex was chosen to supply this product, owing to the company’s distribution of Secugrid in South Africa and the inclusion of its product in Eskom’s design of the substation.
This supply is in line with Fibertex supplying notable projects. The company is supplying construction company WBHO with more than 165 000 m² of Secugrid 200/40 R6 for the new MOGS Tanks that are being built in Saldanha. Further, the company has supplied geosynthetic products worth more than R40-million to Eskom’s Medupi and Kusile power stations.
Baxter is satisfied with the status of the ongoing supply, which has been substantiated by positive feedback from Eskom.
He says Fibertex, with vast geosynthetic solutions in construction and building works for separation, filtration, drainage, protection, erosion control and reinforcement, forms an integral part of structural designs.
He indicates that the substation, which consists of a 400 kV and 132 kV high-voltage yard, provided Eskom engineers with some initial challenges, including a large cut-to-fill operation, which was necessary to create a level platform for the new transformers. This necessitated the erection of a suitable peripheral precast segmental block retaining wall system, which is where Fibertex’s products could assist.
“Because correct geosynthetic reinforcement and drainage design are key to the stability and safety of any retaining structure, rigid Secugrid geogrids were used in combination with a heavy-duty precast concrete segmental block. Fibertex also supplied various components for an advanced subsoil drainage system.”
About 46 550 m² of Fibertex’s polyethylene terephthalate Secugrid 80/20 R6 uni-axial geogrid was installed. Owing to this product’s high residual strength at low strain, it forms an integral part of the block wall by adding tensile resistance to the reinforced soil zone. The wall in question is about 700 m in length, with heights varying from 7 m to 11 m, and was constructed by retaining wall contractor Terrafirma Retaining Walls.
Secugrid is designed to strengthen naturally unstable soil and subgrades so that the composite soil structure can withstand the required loading conditions through an interlocking and frictional effect, with little or no movement in the overlying soil materials over the structure’s lifetime.
This robust reinforcement material is also highly resistant to biological and chemical degradation, as well as installation damage. Secugrid is supplied in rolls and is quick and efficient to install, with minimal demand on labour resources.
Flexidrain, an extruded high-density polyethylene geonet, covered with a Fibertex F-25 polypropylene nonwoven geotextile jacket to form a 500-mm-wide wick-drain composite, was placed at 8 m centres horizontally and 45º to the vertical, between the G7 fill material and the selected granular fill.
The subsoil water is then led to a front collector drain behind the toe of the retaining wall and discharged into Fibertex Drainex DN160 drainage pipes, which are also chemically inert.
The products are being used by Eskom because of the composite reinforcement and subsoil drainage they provide to slopes and walls. Further, Baxter indicates that these products reduce the overall civil engineering construction costs.
He notes that the size of the quantities to be manufactured, and the logistics of importing them timeously, prove to be the biggest challenges. The company leverages its “great team and superior product range” to overcome all the manufacturing and design requirements and logistical obstacles posed.
“There are some wonder- ful geosynthetic solutions available in South Africa and the Fibertex group, with their strategic partners, is among the local and international market leaders in the field,” concludes Baxter.