ENVIRONMENTAL & GEOTECHNICAL Cells being filled with 30 MPa grout, followed by a screed and float or brush finish
Labour-based CANAL CONSTRUCTION Labour-intensive construction (LIC) techniques remain a crucial element in job creation as South Africa tackles growing unemployment in rural and urban areas. A classic case study is the 2004 upgrading of the Hereford canal in Groblersdal, Limpopo, using Hyson Cells’ 3D BubbleLock geocells for the primary structure.
D
uring the upgrading of the Hereford canal, 117 800 m2 of geocells were used to add 29 km to the existing network, bringing the total length to around 44 km. The project was led by main contractor Group Five Civils, which was responsible for the earthworks that formed the canal’s parabolic shape. This
included the establishment of a compacted 200 mm river sand base on which the geotextile was directly placed and anchored, and the daily delivery to site of cement, sand and water for the community-based work teams. In turn, Hyson Cells was appointed as the specialist subcontractor for the installation of Hyson Cells system. Today, the canal remains leak-free and continues to supply water to the surrounding farming community. “On most of our LIC projects, one of our instructors provides on-site training for the contractor and labour on the best ways to rig and fill the cells. A critical component is the sand-cement grout fill material since the
cell construction methodology requires an unconventional cementitious mix design,” explains Sally Hall, director, Hyson Cells. “The end result, though, is a remarkable and consistent 30 MPa strength.”
800 m2 a day For the Hereford upgrade programme, each of the four LIC teams was given an approximately 200 m2 section to complete daily. Cell installation was straightforward, with the main tools required comprising 4 lb hammers and pliers. The Hyson Cells 3D BubbleLock sections, with their unique X&Y rigging, were 75 mm deep and supplied in 200 m² modules measuring 30 m in length. Each team comprised 25 labourers
The employment contract was negotiated and approved by the Groblersdal Department of Labour. Pay was a rate per m² subject to a minimum wage and double-time weekend rate. The rate realised was about 25% above the minimum wage at the time
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IMIESA February 2021
