1998 – Developments in Extreme Flood Estimation Techniques – Hume Dam: A Case Study
J. H. Green and P. I. Hill
Early Probable Maximum Flood (PMF) studies and spillway adequacy assessments for Hume Dam adopted the standards based approach of the time. Since then considerable work and thought has gone into the estimation of extreme floods – both the philosophy and the practice. These changes include the general change in emphasis away from a standards based approach and towards risk assessment; the move towards an AEP-neutral approach for the transformation of extreme rainfalls to extreme floods; and the redefinition of both the PMP and the PMF.
This paper details the effect these and other changes to extreme flood estimation techniques have had on the perceived adequacy of the Hume Dam spillway to pass extreme floods.
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1998 Papers
1998 – Risk Assessment of Dams – Future Directions for Victoria
Learn moreD.Watson, J.Adam
For several years risk management has been promoted by the Victorian Department of Natural Resources and Environment – Water Agencies as the key mechanism for the effective and efficient business management of dams. As part of an extensive water reform program, the Victorian Government announced in October 1997, a financial assistance package for the water industry which included funding for dam improvements covering a majority of large dam owners in the State. One of the conditions for receipt of these improvement funds was the need for each water authority to undertake a Business Risk Assessment of all significant and high hazard dams under its responsibility. This paper discusses the Business Risk Assessment document based on a framework developed by Water Agencies after consultation with the industry and expands on the following reasons why the document was produced:
- To stress the importance and value of risk assessment in managing dams and the major role it plays in business planning and understanding dam performance. Risk assessment is not an alternative to the traditional engineering or deterministic approach but an enhancement,
- To identify the minimum assessment required and examples of different approaches such as portfolio risk assessments,
- To provide preliminary reference risk criteria to assist water authorities to determine appropriate business performance requirements. This preliminary criteria was developed from considering likely (although subject to change) outcomes of the current revision of Australian National Committee on Large Dams (ANCOLD) 1994 Risk Assessment Guidelines and other guidelines involving risk aspects recently or being prepared,
- To indicate future reporting and actions expected over the five year duration of the package including project evaluations and further risk assessments,
- To assist with inputs into ANCOLD’s continuing development and revision of guidelines, and
- To provide a platform for development over the next 18 months of an appropriate regulatory framework for covering all referable dams in the State. Key considerations will included performance based requirements encompassing risk management concepts, appropriate drivers which promote duty of care and associated legal issues and liabilities.
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1998 Papers
1998 – Safety Assessment of Corin Dam
Learn moreJ. Tabatabaei
A safety review of the Corin dam has identified several deficiencies including an inadequate spillway capacity. A hydraulic model test, included in the review indicated that the construction of a 1.3m wave wall along the top of the dam was required to prevent overtopping during the flood of 10,000 years.
The original post tensioning anchors installed along the spillway crest were also identified as unreliable due to inadequate corrosion protection measures.This paper presents safety assessment and aspects of the construction of the remedial works for Corin Dam. As part of the safety review, the condition of the dam was reviewed against the risks of piping, slope instability, flood and seismic forces. The paper also discusses the long term effects of the acidic leakage on the grout curtain and on the integrity of the core.
The risk associated with the flooding during anchor installation and the discovery of a gap formation between the clay core and the concrete spillway wall are also considered.
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1998 Papers
1998 – Risk Assessment of Dams – Future Directions for Victoria
Learn moreDavid Watson and John Adem
For several years risk management has been promoted by the Victorian Department of Natural Resources and Environment – Water Agencies as the key mechanism for the effective and efficient business management of dams. As part of an extensive water reform program, the Victorian Government announced in October 1997, a financial assistance package for the water industry which included funding for dam improvements covering a majority of large dam owners in the State. One of the conditions for receipt of these improvement funds was the need for each water authority to undertake a Business Risk Assessment of all significant and high hazard dams under its responsibility.
This paper discusses the Business Risk Assessment document based on a framework developed by Water Agencies after consultation with the industry and expands on the following reasons why the document was produced:
- To stress the importance and value of risk assessment in managing dams and the major role it plays in business planning and understanding dam performance. Risk assessment is not an alternative to the traditional engineering or deterministic approach but an enhancement,
- To identify the minimum assessment required and examples of different approaches such as portfolio risk assessments,
- To provide preliminary reference risk criteria to assist water authorities to determine appropriate business performance requirements. This preliminary criteria was developed from considering likely (although subject to change) outcomes of the current revision of Australian National Committee on Large Dams (ANCOLD) 1994 Risk Assessment Guidelines and other guidelines involving risk aspects recently or being prepared,
- To indicate future reporting and actions expected over the five year duration of the package including project evaluations and further risk assessments,
- To assist with inputs into ANCOLD’s continuing development and revision of guidelines, and
- To provide a platform for development over the next 18 months of an appropriate regulatory framework for covering all referable dams in the State. Key considerations will included performance based requirements encompassing risk management concepts, appropriate drivers which promote duty of care and associated legal issues and liabilities.
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1998 Papers
1998 – Geotechnical Assessment and Rehabilitation Challenges for Tailings Dams in China
Learn moreSteven Rosin and Chen Han Shan
Tailings dam rehabilitation is a major challenge for the mining industry in China requiring a multi-disciplinary approach. A team of Chinese and Australian professionals have recently completed a 4-year project to develop guidelines for rehabilitation procedures for tailings dams in China.
This paper focuses on the geotechnical stability issues that were required to be addressed as part of dam rehabilitation assessment. It also discusses Chinese practices in tailings dam design and operation considered for the assessment. Three case studies are presented from sites in various parts of China.
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1998 Papers
1998 – Granit Ground Anchorage Integrity Testing – An Innovative Anchorage Condition Monitoring Procedure
Learn moreD. B. Edwards, B.H. Jackson & R. H. Wright
Ground anchorages are installed to support structures such as dams, slopes and tunnels. Failure of anchorages could be serious.
The condition of these critical supports is currently assessed by monitoring the load in the anchorages by either load cells or lift-off testing (jacking). Both methods are expensive and testing may damage the corrosion protection beneath the anchorage head.
A non-destructive testing method for ground anchorages needed developing and the UK Universities of Aberdeen and Bradford developed a testing system called GRANIT with patent applications on the system filed world-wide.
Full scale measurements were conducted during the construction of Penmaenbach and Pen y Clip Tunnels on the UK’s A55, where rock support was provided by prestressed rock anchorages. In all 9000 records of anchorage response were analysed.
A major finding from the research was that the response of the anchorages to the dynamic impulse motion produced by the blast loading depended on how the anchorage had been constructed and on the nature of the surrounding rock mass. If the prestress load in the anchorage was changed, or the free length increased, a noticeable change was observed in the response ‘signature’ as monitored by an accelerometer located at the anchorage head.
Applying a known impulse load to the anchorage head immediately after construction and measuring the response, provides a datum response signature for the intact anchorage. If the anchorage was to deteriorate in any way, eg loss of prestress, this should be noticeable on subsequent response signatures. This approach is the basis of the GRANIT system.
A short programme of anchor calibration testing for bolts was conducted in Hawkesbury sandstone in Sydney during March 1998 and developments in Australia and UK are proceeding.
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