The lowdown on RCC3 February 2009
A specialist training seminar was held recently in Australia to educate practitioners and young engineers on the design and construction of RCC dams
More than 170 international delegates gathered in Australia for a structured training seminar to discuss specialist RCC dam techniques and new technology. The purpose of RCC 08 was to help achieve better quality and more cost-effective dams through greater awareness and understanding. Topics under discussion included:
• Tracing the history and evolution of RCC.
• Avoiding costly and risky mistakes.
• Finding better designs and methods.
• Using the most appropriate equipment.
• Knowing who to ask for help.
RCC 08 also took the initiative in taking more of a teaching than a presentation approach. As Shane Dunstan from ARAN International explained: ‘We did not invite speakers to submit papers on a topic of their choice. The aim of the seminar was to educate practitioners and young engineers in the basic principles for designing and constructing RCC dams. When developing the programme we gathered a group of international seasoned experts and together we developed a list of topics to be discussed. All presenters were encouraged to present information free from bias and to draw on the broadest range of design and construction practices possible.’
RCC 08 wanted to bring the dam building fraternity together for educational purposes. On the one hand delegates and speakers are competitors, but at seminars like this they are keen to share their passion and experience of RCC dams with one other.
Opinions versus principles
John Green knows all about competitiveness and is a specialist estimator who has been involved in estimates for 17 RCC dams worldwide. ‘We’re not in rocket science in RCC,’ he said. ‘The good thing is that RCC is still in its infancy. We have to be inventive. The real fun part of the game is the competitive tendering. It spurs you on to look for innovative solutions. For example I believe that the Chinese have used cableways to place RCC and I have also worked on one dam where we were very close to using recycled concrete.
‘With RCC you have to avoid the tyranny of status quo. If you’re not careful you’ll find yourself with people who say it’s done like this on that job and so you should do the same on this too. You have the tremendous opportunity to be inventive,’ he told delegates. ‘When approaching an RCC project you must have an open mind. Don’t have pre-conceived notions.’
Dave Murray, senior project manager for dams at Queensland Water says that dam owners don’t have time for pre-conceived ideas. ‘We don’t care about strongly held opinions,’ he said. ‘We just look at the best value for money. Strongly held opinions don’t take us anywhere as an owner.’
‘You need to listen carefully and divide strongly held opinions from soundly based principles,’ Trevor Dunston from ARAN International went on to tell delegates. ‘It’s up to you to split the difference.’
Worldwide, RCC is becoming the method of choice in dam projects and it is a successful cost-effective solution. But, as John Green emphasises, you must not settle for ‘comfortable tendering’ on an RCC project.
‘Every job is different and you’ve got to treat it differently. But you’ve also got to set out to learn more about that project in a competitive tender than anyone else knows,’ Green said. ‘The general philosophy to apply is to treat a big job as a small job and vice versa. Give a small job the respect it deserves and don’t be overwhelmed by a big job. You’ve got to be competitive. Making every effort to take a dollar out is very important.’
Pozzalan provides a good opportunity to be innovative when pricing for an RCC project, but Green warns that you have to have the time to develop it if using local resources. For example, in Asia rice husk ash can be a good pozzalan, while volcanic ash, crushed brick and fly ash can also be used.
Engineering terminology can also play a part in the cost-effectiveness of a good RCC projects. ‘In general, when people talk about RCC in engineering terminology they talk about compacted m3. To me there is no such thing as m3 in earthworks,’ Green says. He believes that the precise nature of m3 should be clarified. Australian company ARAN has set the pace in their literature by talking about compacted m3. ‘The difference between compacted and loose m3 in RCC can be as much as 20%,’ Green said. ‘I’ve even seen more than that and this can make a big difference.’
Having a model of a good check list when estimating the duration of the job can also make a difference. ‘You need to establish all factors and look at the job on its merits and use your judgement when estimating,’ Green said, listing factors to include:
• General operational efficiency.
• Mechanical efficiency.
• Learning curves.
• Foundation delays – as these are often so undulating.
• Gallery restrictions – can impact on productivity of the total system.
• Finishing restrictions – at the top of the dam it becomes narrower and so there is less room for equipment which affects work efficiency.
• General placing delays.
Reverse factors or interruptions that can cause delays include:
• Placing waterproof membranes.
• Layer joints.
• Wet weather delays (can include flooding).
• Hot weather delays.
• Programming delays.
Another important point Green covered was the handover of a project from the project estimator to the construction people. ‘It is extremely important,’ he said. ‘The estimator should insist on a proper handover if you want your organisation to kick a good goal.’
RCC down under
Keynote speaker, Graeme Newton, helped to give an Australian perspective on RCC dams. Newton is CEO of Queensland Water, Infrastructure Pty. This is a specialised vehicle established by the Queensland government to gain approval for and deliver major water infrastructure projects to help solve the state’s water supply crisis. Queensland currently has high level water restrictions. Massive population growth over the past ten years combined with a drought has compounded the need for building new dams. These include the Traveston Crossing and Wyaralong dams, both of which are likely to be built using RCC technology.
Traveston Crossing dam on the Mary river is a proposed A$1.6B structure. Currently still undergoing the relevant approval, construction is due to start early this year with completion scheduled for 2011. With a 153,000Ml capacity, it will contribute to 27% of the additional water supply required by 2015 and supply enough water for 800,000 people in southeast Queensland per day.
The project has been packaged to benefit large, medium and small firms within the construction sector and encourage and foster growth in the industry. Market research has been commissioned to gain a greater understanding of current market conditions and to deliver a high performance team to manage the project. In the long term the University of the Sunshine Coast in Queensland will study the long term benefit the project has for local industry and will assess the best way to utilise local suppliers.
Wealth of experience
RCC 08 was held from 9-11 April 2008. Expertise was drawn from eminent professionals involved in the field of RCC, including:
• Brian Forbes – manager of major dam projects for international consultants GHD, Australia. Forbes was the principal engineer/reviewer for eight of the first nine RCC dams to be built in Australia. Since then he has worked on over 30 major RCC dams in 15 countries.
• Francisco Ortego – principal and director of FOSCE Consulting Engineers in Germany. He has been involved in the planning, design and construction of more than 50 large RCC dams in 20 countries.
• Ken Hansen – senior vice president of Schnabel Engineering in the US. He has consulted on more than 55 RCC dams in 11 countries.
• Trevor Dunstan – executive director of ARAN International in Australia. His continuous mix, volumetric proportioning plants have been used on more than 30 RCC projects with volumes up to 1Mm3.
To obtain DVD proceedings of RCC 08 or for more information on any future events, please contact [email protected]