Leading geotechnical solutions company Esor, part of the JSE-listed Esorfranki group, recently completed the excavation of Gautrain pier foundations consisting of six 7-m-diameter shafts at depths ranging from 21 to 29 m. The Centurion contract, awarded to Esor by Bombela Civils Joint Venture (CJV), was valued at approximately R34 million.
This set of six articles covers the design, hydraulic, geotechnical and structural challenges associated with the construction of seven viaducts in the southern section of the massive and visionary Gautrain project. The authors wish to acknowledge the kind permission given by the Gauteng Provincial Government and the Bombela Concession Company to publish these articles. The authors also wish to advise that the views and opinions expressed are solely those of the authors and not those of the Province or Bombela.
A full hydrological and hydraulics analysis at each of the viaduct river crossings was undertaken and evaluated to identify the potential impacts of the viaduct and to design remedial measures that would minimise the predicted hydraulic and environmental impacts. Both the short-term impacts associated with the construction phase and the resulting long-term conditions were assessed. The analyses focused on changes in river flood levels and erosion potential along the river channel and on scour at the viaduct piers and abutments.
The seven southern section viaducts, with a total length of some 4,3 km, traverse a variety of geological units. Preferential weathering in the upper reaches of the profile necessitated that two main founding solutions be adopted: piles and spread footings. The spread footing founding depth varied from 3 to 7 m while that for the piles approached 30 m in places. Table 1 details the foundation attributes.
The substructures of the viaducts were designed and detailed by Nyeleti Consulting. Close liaison between the geotechnical engineers (ARQ) and the superstructure designers (Vela VKE and Pöyry) was required in the detailed design of the substructures. The design forces for the substructures were obtained from a global analysis which was carried out for each viaduct by the superstructure designers.
The successful design, manufacture and construction of the viaduct superstructure with its precast segmental format was the key to the timeous completion of these sometimes vast structures. Reaching the final solution required extensive planning and interaction between the design subconsultants (VelaVKE), the Bombela Joint Venture supervisory team, the casting yard where the segments were to be manufactured, and VET , the viaduct erection specialists.
A quality improvement in the production of any precast concrete product generally involves an increase in costs. So when better quality, which in this instance means strength, durability and impermeability, is achieved with a decrease in costs, the method by which this win-win situation is achieved bears close scrutiny.
The incrementally launched construction system is best suited for the construction of bridge decks for railways and freeways over difficult terrain where it is not possible to erect staging, such as over rivers and ravines.
Given today's systematic approach to project and risk management, it is tempting to believe that projects are not only fail-safe, but also executed within budget, on schedule and are of the intended scope. Unfortunately this is not always the case, and as a result many projects and companies fail due to unforeseen and unidentified risks during the entire life cycle of projects. Current methods, although advanced and thoroughly thought through, have a number of shortcomings when it comes to project risk. The consequences of these shortcomings are numerous and often troublesome.
On Tuesday 27 January 2009, 22 eager engineers boarded a bus, sponsored by the Trans Caledon Transfer Authority, to embark on a site visit organised by the SAICE Project Management Division (PMD) to the Vaal River Eastern Subsystem Augmentation Project (VRESAP).
The 'power crisis' is a well-known and daily experienced reality facing South Africa. Eskom has placed huge emphasis on its capacity regrowth and electricity generation plans. Demand for and growth in electricity supply is also on the rise in countries bordering South Africa. Babcock Ntuthuko Powerlines (BNP), which has been in existence for the past 55 years as a market leader in powerlines construction, is currently also managing powerlines projects in Namibia and Botswana for their respective power utility departments.
On 11 June 2010 kick-off will take place at the Soccer City Stadium in Johannesburg. PPC Cement, who supplied 90% of the cement used to construct the stadium, kindly provided these photos of the stadium nearing completion. According to Dr Orrie Fenn, PPC's Chief Operating Officer, this project fits in perfectly with PPC's philosophy of contributing towards 'building the nation', as Soccer City will remain a key sporting and cultural facility well beyond the 2010 FIFA World Cup.
Initially , in the Northern Cape, as elsewhere, there were no roads. On the ocean fringes the Strandlopers had adjusted their lifestyle so that they operated in a narrow coastal strip. In the interior were the hunter-gatherers, who were by definition nomadic, requiring water and a source of food. These requirements were catered for by following the herds of wild animals during their seasonal migrations. The routes were selected and beaten out by the game, which of course chose routes with sufficient access to water. The game in turn provided food for the hunters. There was no need for roads.