The Civil Engineering Contractor August 2018 | Page 27

TECHNOLOGY will be confined to Lesotho with the objective of radically increasing water flow through the transfer tunnel by constructing a new dam in the Lesotho water catchment. Unpredictable occurrences on site, says Jackson, consist either of geotechnical reports sometimes being wrong or not done, resulting in hard rock being unexpectedly found — and theft. Jackson fondly recalls his toughest project, where he was required to prove the worth of the Brokk equipment his business sells: “The client would only pay for the equipment once it was proven successful on site. It was a new concept and a new technique to South Africa at the time, and he would only pay once the machine’s capabilities were proven on site over two weeks. His scepticism was because their first-choice e quipment had failed to meet demanding specifications. The efficiency of our machine is now well known — but it was nerve-wracking that first time.” viable such projects that previously might have been too complicated and difficult to be attempted. Though, according to Gautrain's Van der Merwe, tunnel construction can be 100 times the cost of surface construction, Ferreira says this is nowhere near the case when building basements. “It is more expensive, but it is not like tunnelling. Once the lateral support has been completed, we are effectively just changing the working platform level.” He says a lot of the work around the Gautrain project — which Franki Africa was involved in with building stations and parking areas in Rosebank, Sandton, and Hatfield — is normal construction work involving lateral support. Three challenges Ferreira lists three key challenges surrounding traditional underground construction: • With a lot of civils work taking place in highly built-up areas such as Sandton, hitting underground services is one of the major risks. “When you’re inserting piles and anchors, service lines such as electricity, water, and fibre optic cables have to be avoided in such a Technology has improved to the extent that projects involving the underground component of city buildings can be designed more expansively than even a decade ago, explains Victor Ferreira, group business development manager at Franki Africa. The company is the local subsidiary of Keller, one of the biggest geotechnical contractors in the world, and from which the company gets access to the best technology and support in the world, he says. Fifteen years ago, we wouldn’t have thought of excavating basements as far down as 30m. Advanced technology enables us to go deeper underground than was previously possible, using bigger anchors and piles and better analysis methods.” It also makes World class With a TBM, the entire process has to be automated or a bottleneck occurs.