2006 – Failure Modes Analysis as Applied at Rocklands Dam
Marius Jonker, Malcolm Barker and Gary Harper
This paper provides a framework for conducting an effective Failure Modes Analysis. It explains the fundamental principals and methods of Failure Modes Analysis. The current international state of practice on Failure Modes Analysis is discussed, and the objectives, benefits and limitations of Failure Modes Analysis assessed. Guidelines are given on how to apply the outcome of Failure Modes Analysis in dam safety management and surveillance.The effective application of Failure Modes Analysis is illustrated in a case study where the process was applied in the safety review and risk assessment of Rocklands Dam for Grampians Wimmera Mallee RegionWater Authority in Victoria.
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Papers 2006
2006 – Recent Advances in the Seismic Analysis of Intake Towers
Learn moreJohn Bosler and Francisco Lopez
The ANCOLD “Guidelines for the Design of Dams for Earthquake” were published in August 1998. The guidelines contain a brief outline of the performance requirements and recommend, in general terms, a method of analysis for intake towers.
Over the last three decades there has been considerable research on the seismic performance of intake towers as they move into their inelastic range. In the years following the publication of the ANCOLD guidelines, some of the findings from this research have been incorporated into revised design procedures issued by the US Army Corps of Engineers. These procedures, if embraced by ANCOLD and the local dam engineering community, are likely to have a significant impact on how the structural adequacy of existing towers under seismic loading are assessed.
Rocking behaviour in which the tower becomes unstable as a transient condition has long been recognised as acceptable under certain conditions. Attempts to prevent tower rocking by measures such as retrofitting tensioned ground anchors may, in some situations, be of limited value in improving the seismic performance of a tower and could result in an increase in bending moments in the tower stem. Guidance is now available on the amount of rocking behaviour that is tolerable.
For seismic events greater than the Operating Basis Earthquake most towers will start to exhibit inelastic behaviour. Specific guidance is also now available on the length of time during an earthquake that bending moments in excess of the elastic capacity can be tolerated, the amount by which these moments can exceed the nominal bending moment capacity and the vertical extent of the tower stem that can be stressed beyond its elastic limit.
The paper discusses the different approaches taken by ANCOLD and the Corps of Engineers. Key differences in outcomes are highlighted using a worked example for a typical reinforced concrete tower and the ANCOLD approach is found to be generally, but not always, more conservative. The paper concludes with recommendations for dealing with these differences.
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Papers 2006
2006 – Design and Construction of the Gattonvale Offstream Storage
Learn moreNerida Bartlett, David Scriven, Peter Richardson
The failure of a number of consecutive wet seasons has resulted in storage levels in Eungella Dam being at dangerously low levels such that supply could be exhausted by June 2007. Eungella Dam supplies bulk water to the Bowen Basin coal fields as well as the Collinsville power station and the Collinsville township.
The Collinsville township, power station and coal mine as well as the Newlands mines take water from the Bowen River Weir which is supplied from Eungella Dam some 95 kilometres upstream. Transmission losses of the order of 25 to 50% have been experienced for releases from Eungella Dam to Bowen River Weir.
The Eungella Dam catchment area is 142 square kilometres. Significant flows occur in the Bowen River downstream of Eungella Dam, the catchment area above Bowen River Weir being 4,520 square kilometres. The topography in the surrounding area (near Collinsville) is not suitable for dam construction.
The opportunity existed for the construction of an offstream storage adjacent to the Bowen River Weir so that the downstream flows could be captured reducing the demand on Eungella Dam thus making more water available for upstream users.
A 5,200 ML offstream storage, associated pump station and rising main was designed, constructed and filled within a period of 12 months.
Foundations at the site are highly permeable sands. Marginally suitable clay for a seal was in short supply as was suitable rock for slope protection. A fixed price budget had been set by the contributing customers.
This paper describes the hydrology, site conditions, design and construction of the project.
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Papers 2006
2006 – The Requirement for Dam Instrumentation from a Queensland Regulatory Perspective
Learn morePeter Allen
The Requirement for Dam Instrumentation from a Queensland Regulatory Perspective ANCOLD 2006 Conference – Instrumentation and Survey Seminar Page 1 THE REQUIREMENT FOR DAM INSTRUMENTATION FROM A QUEENSLAND REGULATORY PERSPECTIVE Peter Allen, Director Dam Safety (Water Supply) Department of Natural Resources and Water ABSTRACT This paper presents the Queensland dam safety regulator’s views on issues to be considered when designing and implementing instrumentation for referable dams in Queensland. It also summarises the general requirements for dam instrumentation contained in the Queensland Dam Safety Management Guidelines and gives some thoughts on what should be contained in any ANCOLD Instrumentation Guideline.
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Papers 2006
2006 – Performance of New Orleans’ Hurricane Protection System: The Good, The Bad, and The Ugly
Learn moreG.L. Sills, N.D. Vroman, J.B. Dunbar, R.E. Wahl
In August 2005, Hurricane Katrina made landfall just east of New Orleans and inflicted widespread damage on the Hurricane Protection System (HPS) for southeast Louisiana. Subsequent flooding was a major catastrophe for the region and the Nation.
The response to this disaster by the U.S. Army Corps of Engineers included forming an Interagency Performance Evaluation Taskforce (IPET) to study the response of the system and, among many lines of inquiry, to identify causes of failure of levees and floodwalls. Beginning in September 2005, the IPET gathered geotechnical forensic data from failed portions of levees and floodwalls. Major clues discovered at the 17th Street break, including clay wedges dividing a formerly continuous layer of peat, led to an explanation of the failures. Field data from the failure sites were interpreted within the regional geologic setting of the New Orleans area to identify geologic and geotechnical factors that contributed to the catastrophe. The data gathered provided a method that resulted in the “IPET Strength Model.” This strength was used in analyses of the I-walls and levees using limit equilibrium stability analyses, physical modeling using a powerful centrifuge, and finite-element analyses. The results of all three types of studies revealed a consistent mode of failure that included deformation of the I-walls and foundation instability. The IPET also studied non-failed I-walls at Orleans and Michoud Canals, to identify geotechnical, structural, and geologic distinctions between failed and non-failed reaches.
Performance of the HPS during Hurricane Katrina offered many lessons to be learned. These lessons learned include: the lack of resiliency in the HPS; the need for risk-based planning and design approach; the need for the examination of system-wide functionality; and knowledge, technology, and expertise deficiencies in the HPS arena. In addition, understanding of the failure mechanisms and related causes of the levee and floodwall breaches provides a new direction for future designs of hurricane protection systems.
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Papers 2006
2006 – Meeting the Challenges of Tomorrow, Today – Human Resources – A Changing World
Learn moreKaren Soo Kee
Strategic resource management has never been more important than it is today with the aging of the “baby boomers” and their ongoing exodus from the workforce. The vacancies they leave in professions such as engineering are just beginning to be felt and will exponentially escalate over the next few years. Specialised professions such as dam engineering and related professions will be hit the hardest as the knowledge and skills learnt over decades are depleted.
The lack of skilled staff and in fact the lack of interest of young engineers in entering the dam industry is one of the critical challenges for today. How do we attract professional staff into the field of dam safety before the exodus creates a “black hole” that can never be filled? And how can we ensure the knowledge transfer from existing skilled staff to newer staff to retain expertise within the industry?
Another issue for resource management is that tomorrow’s workers, the “X &Y generations”, will be unlike the current and previous generations of workers. These workers will be less likely to have a mortgage, will have fewer children and be more interested in lifestyle, not career. They will be extremely confident, well-educated and very mobile. The future will be a sellers market. The challenge here will not only be to attract and recruit talented workers but also to retain them.
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