Africa | Time for change?
Dr Quentin Shaw, Director of ARQ Consulting Engineers and ICOLD Vice-President for the Africa Zone, shares his experiences in the industry and comments on the development of dams in Africa, explaining why he believes it is time to change project implementation models in the region
Above: Dr Quentin Shaw. Shaw was elected in 2022 as ICOLD Vice President for the Africa Zone
I STARTED MY CAREER in dams in 1984, having graduated from the University of Birmingham (UK) and venturing out to South Africa to work for the then Department of Water Affairs and Forestry. Over the following 10 years, I gained some incredible experience in the design and construction of dams, and particularly the first two Roller Compacted Concrete (RCC) arch dams in the world, Wolwedans Dam & Knellpoort Dam. Since then, I have been involved in dam projects in a further 35 countries, retaining a particular focus on RCC and arch dams. The summit of my dam design involvement to date was as chief dam designer for construction design and implementation of the 275m double-curvature conventional mass concrete arch Yusufeli Dam, currently in the process of first impoundment in Turkey. Having had a role in most of the non-Chinese
technology RCC arch dams constructed around the world to date, I received the ICOLD Innovation Award in 2018 for my work in developing the understanding of early stress-relaxation creep (SRC) in RCC dams, which technology was recently put to use in demonstrating that Gross Dam in Boulder, Colorado could be raised in RCC and converted from a curved mass concrete gravity dam into an arch-gravity dam without having to post-cool the new concrete and grout contraction joints. The related understanding implies a different methodology for the thermo-mechanical analysis of RCC dams, compared to that traditionally applied for conventional mass concrete dams. After comparing prototype and modelled behaviour
Below left: Wolwedans Dam in South Africa
Below right: Changuinola dam in Panama
on Wolwedans Dam in South Africa, I was fortunate to be able to take my observations into the design of Changuinola 1 Dam, another RCC arch-gravity dam, in Panama. Expecting the same low SRC characteristics of the fly ash-rich RCC that were observed at Wolwedans, I included comprehensive instrumentation in Changuinola 1 during construction, which was completed in 2011, to enable a definitive measurement of the expected effects. Subsequently being involved in the safety monitoring of
the dam over the following 10 years, I was able to fully substantiate and replicate in modelling the significant and quite surprising structural consequences of low SRC in horizontally-constructed RCC. Wolwedans Dam and Changuinola 1 Dam are two of the 20 RCC dams, of over 900 to have been constructed to date, that have been recognised as “International Milestone RCC Projects”. While the Yusufeli Dam project presented many challenges, the two biggest were undoubtedly the very complex and heterogenous foundation conditions and adapting and controlling very rapid concrete post-cooling to allow each stage of contraction joint grouting to be achieved sufficiently rapidly to keep up with the record-breaking average monthly concrete placement rate of 140,000m3
. The development of
a very detailed finite element foundation model and procedures to improve and verify the improvement of the foundation rock mass has so far meant a very accurate alignment of predicted and measured behaviour during impoundment. On a substantially smaller scale, I have been
extensively involved in the development of rubble masonry concrete (RMC) arch dams, which is a labour- based construction technology that brings together a 19th century material with modern structural analysis to present an extremely cost-effective and durable dam type in an environment where low cost labour is abundant, as is the case in many countries across the developing world. No other dams technology puts more of the project capital cost back into local labour wages and local skills development. Over the past twenty five years, we have implemented more than 18 RMC dams, with several more currently in the pipeline.
Dam engineering Having started ARQ Consulting Engineers in South
Africa in 1993 with two partners, I was responsible for the company’s operations in dam engineering for almost thirty years. More recently, I have taken on
16 | March 2023 |
www.waterpowermagazine.com
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