Construction World September 2018

GEOTECHNICAL ENGINEERING

EARTHFORM THE PERFECT SOLUTION When a couple in Thohoyandou, Limpopo, decided to build their dream retirement home they were faced with an unexpected challenge: soil erosion due to the high lying area of their land. A Google search highlighted Technicrete’s Earthform

“I knew that Manie Troskie from Engineered Interlock Solutions (EIS) was a specialised concrete block retaining wall contractor that has many years of experience in the design and building of concrete block retaining walls as he is a regular customer of ours. Due to the massive size of the project and the challenging terrain, I referred the couple to Troskie for the retaining wall installation and design,” said Hilton. Troskie said “EIS designed and constructed the retaining wall in various stages. The critical area was in front of the house where 80 mm wide tension cracks already had developed. There was a risk that this embankment could collapse. A total slip failure would have had a major impact on the structural integrity of the house. The in-situ embankment was cut back to the required design distance for the Geosynthetics reinforcement and drainage to be installed. The soil was stockpiled for reuse”. “The fill wall was constructed in two terraces, each 3 m high. The terraces were of a more economical design solution and provided a softer look for landscaping. There were various smaller terraced walls constructed on both sides of the house. One wall was con- structed as a 7 m high continuous wall that flared out into three smaller terraces,” said Troskie. “The wall behind the house in the cut section was also designed as a two-terrace wall. The bottom section was 5 m high and the second wall 3 m high. There is an access road to the neighbour’s property on top of the wall. This required that embankment was cut back and the soil stockpiled to provide space for the Geosynthetic reinforcement and drainage”. Troskie added, “This is the biggest residential retaining wall proj- ect that we have undertaken to date. We happily used the recommended Technicrete Earthform retaining wall blocks because we ourselves have used them in the past on other projects due to the quality of the block and its longevity “. “Over 20 000 grey Earthform blocks were needed to complete the Thohoyandou project. The house was situated off the main tarred road, and this is where the expertise of the Technicrete drivers came to the fore as they battled dirt roads, at times in bad rainy weather, and still delivered on time as scheduled without breakages” he said. “The access to stock as required and competitive pricing are other factors that made working with Technicrete a win-win situation over the eight months that it took to complete this project. The technical advice from Peter Hilton was spot on for this development and the couple involved were very happy with the end result in terms of erosion control and final appearance” said Troskie. Earthform retaining wall blocks can be stacked up to 7 m high provided that sufficient Geosynthetic reinforcement, erosion control layers and drainage are installed in the reinforced fill section directly behind the Earthform retaining wall blocks. Plants or vegetation suited to the style of the Earthform retaining wall blocks should be planted facing outward of the front face of the wall and require little maintenance. 

“O ur Earthform retaining wall blocks are ideal for the kind of challenges the couple was facing. The longevity of the prod- uct has stood the test of time on many projects where soil erosion has been vast due to flooding,” said Peter Hilton, Sales Consultant for Technicrete in Polokwane. Due to the magnitude of the project, Hilton travelled to Thohoyan- dou to assess the site and take the required measurements, which took over two hours. The house, large enough to accommodate four children and extended family, was built high up in the magnificent hilly area of the region affording the property exquisite views, but the heavy rains were causing massive soil erosion on the chosen site. Hilton added: “Earthform gives embankments a natural support while protecting the land from collapsing due to erosion. Additional- ly, it provides an attractive and practical finish in difficult to maintain steep areas through the creation of plantable and easy to maintain retaining walls”. retaining wall blocks as a solution. Meeting with Technicrete at their Polokwane office offered them the erosion solution they required.

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CONSTRUCTION WORLD SEPTEMBER 2018 I