75th Anniversary | Below, from top to bottom:
Bakubung RMC Dam, South Africa Bellair RMC Dam, South Africa
Aloe Cove RMC Dam in South Africa
Africa said to me that Wolwedans Dam was a
project of a lifetime, implying that you only get to be involved in one project of that size and importance. These words echoed with me when I was given the opportunity to fill the role of chief dam design engineer on the 275m high Yusufeli double-curvature concrete arch dam in Turkey. Yusufeli Dam really was the project of a lifetime. Despite very complex geotechnical conditions,
which included the need for significant foundation improvement and improvement verification, the most complex and detailed foundation model yet developed for a dam design was established and calibrated through back-analysis during construction, to ensure a remarkable level of accuracy in the impoundment verification analyses. Impoundment followed a six-stage process, checking measured arch performance against modelled predictions at each stage to confirm that performance was in line with the design expectations. Accurately establishing the temperature state of the structure at each stage, the precision of the replication of the actual behaviour compared to that predicted, allowed high levels of confidence in safety during first impoundment. From 2019 onwards, I have been involved in the
Gross Dam Raise project in Colorado, US, where we have developed new models for the thermo- mechanical analysis of the RCC raise, based on the behaviour observed at Wolwedans , Changuinola 1, Kotanli and Koröğlu dams, as well as laboratory and full-scale trial testing. The raising is being constructed with a fly ash-rich, high-workability, low stress- relaxation creep RCC and I have been involved in the analyses, the instrumentation, materials testing and trials and am currently the RCC mix design lead. It is very important to differentiate the RCC arch
technology in which I have been involved from the RCC arch dam technology practised in China. Whereas the Chinese RCC arch technology involves the construction of a concrete arch dam in RCC, the RCC arch technology to which I refer is about an RCC dam that gains benefit from three-dimensional structural function. The difference is important in the sense that the Chinese technology implies substantially compromised average rates of RCC placement (maximum to date = 28,000m3/month), whereas the technology in which I have found great efficiency is no different in achievable placement rates to an RCC gravity dam. In total, I have to date been involved in the design and construction of 43 new dams and the raising and rehabilitation of a further 15 dams in 39 countries. I am not an advocate of any one particular solution when it comes to dam types, or particular construction approaches and believe in finding the best solution for each particular circumstance. For example, while RCC is a great solution when horizontal construction offers maximum efficiency, it is undoubtedly not the best solution on a site and dam configuration best-suited to vertical construction. While it is accordingly significant to note that an average rate of conventional concrete placement of 142,000m3/month was achieved at Yusufeli Dam, which rivals the best achieved to date at RCC gravity dams, I have also been involved in the design and construction of 14 rubble masonry concrete (RMC) dams to date. RMC dam construction is a technology that I
borrowed from Zimbabwe, where I first saw it used for the construction of an arch dam in 1994. Without going into the reasons for its development in that country, it has proved exceptionally efficient for the construction of durable dams in countries with abundant, low-cost labour. With a cost as low as 30% of other alternatives, more labour employment and skills development are created with this technology than any other form, or type of dam construction.
60 | May 2024 |
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