Kurt Douglas, Matt Spannagle and Robin Fell
This paper describes a method for estimating the probability of failure of concrete and masonry gravity dams through the dam or the foundation. The method is based on the research and analysis of historic failures and accidents performed at The University of New South Wales over the last two years. The method accounts for dam type; age; foundation; height/width ratio; dam performance observations; and monitoring and surveillance.
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Brian A Forbes and Jon T Williams
The 43 metre high Cadiangullong Dam was constructed during 1997-1998 to supply untreated water for the Newcrest Cadia gold mine near Orange in NSW. The placement of the 110,000 m3 of RCC was performed without expensive thermal control techniques in an area of extreme climate conditions. Thermal finite element studies were undertaken during design to assess the effect of the climate extremes on construction and assist in the design of contraction joints. An RCC mix with sand proportions in excess of 50% of the fully crushed aggregate by weight was used to eliminate segregation. This also had the effect of requiring a low compaction effort to achieve density but exhibited a sheared surface texture if placed over wet. Following full scale trials the conventional concrete facing was superseded during the early stages of construction with an in situ modified RCC facing. The modified RCC consisted of a grout enriched internally vibrated RCC (GE-RCC) to provide a durable, impervious upstream face. This paper discusses the details of these three aspects and provides design, construction and performance data to date.
Mark Foster, Robin Fell and Matt Spannagle
This paper describes a method for estimating the probability of failure of embankment dams by piping. The so called “UNSW method” is based on the results of an analysis of historic failures and accidents of embankment dams. An estimate of the probability of failure of a dam by piping is made by adjusting the historical rates of failure by piping by applying weighting factors which take into account the dam zoning; filters; age of the dam; core soil types; compaction; foundation geology; dam performance; and monitoring and surveillance. The method is intended for preliminary assessments only and is ideally suited as a risk ranking method for portfolio type risk assessments to identify which dams to prioritise for more detailed studies and as a check on event tree methods.
Over the last 30 years, the demand for water storages in Queensland’s Mary’s River has grown significantly. As a result of this growth in demand it was decided to raise Borumba Dam, the major storage on the system, in two stages The first stage was to be approximately 2 metres in I997 and the 25 metre raising be required in about 2010.
Borumba Dam was completed in 1964. It is a 43 metre high concrete faced dam with a 32 metre long on the left abutment. The first proposal for initial raising was to install a two metre high air-inflated rubber dam on top of the existing crest. However, it was determined that this method of raising presented a number of prob and a new solution was sought.
Steve Everitt, Ron Fleming, Lelio Mejia
The Electricity Corporation of New Zealand Ltd (ECNZ) is strengthening its Matahina Dam which is an 80 m high, 400 m long rockfill dam impounding a 60 million cubic metre reservoir. The strengthening is to ensure the dam will withstand potential fault displacement within the dam foundation.
ECNZ’s management of the project is described from the design and consents phase through to construction. Key issues are discussed which have contributed to the success of the project such as management structure, the International Review Board, the design process and risk management.
A dam owner is often surprised to learn that his dam has been listed on a heritage register. This is often the first indication that the dam has heritage significance.
This paper discusses the different types of heritage listing and what the implications are for an owner. It suggests that a prudent owner will find out whether he needs a heritage conservation plan, particularly where redevelopment or remedial work at the dam is contemplated. The paper describes the content of a typical conservation plan for a large dam and how it is implemented.