Ben Ross, Jason Brown, Richard Rodd
Goulburn Weir was constructed in 1891 forming Lake Nagambie on the Goulburn River, approximately 8km north of Nagambie in Victoria. It is a key asset in the irrigation network diverting water to 352,000ha in Northern Victoria. The weir was remodelled between 1983 and 1987, replacing 21 overshot gates with nine radial gates. A series of 28 post tensioned bar ground anchors were installed to secure the radial gate concrete support piers to the weir’s mudstone foundations. On 8 March 2006 during routine testing of the pier bar ground anchors, failure of one anchor occurred. It posed a possible risk to pier stability. Subsequently investigations into the cause of failure and its implications was undertaken consisting of a program of data review, site investigations, metallurgical testing, geotechnical investigation, design reviews and stability assessments. It was recommended to replace the failed anchor and 10 other under performing anchors with 8 cable strand anchors at the cost of approximately $1million.
Key words: Risk, bar anchor failure, stability assessment, anchor construction.
Jonathon Reid, Chris Kelly, Bob Wark
One of the most important aspects in the construction of an embankment dam is to be confident that the filter materials placed meet the design intent. The design methodology for filters is now well documented.
However, all too often during construction the filter material, as placed, does not comply with the specified requirements and all parties are faced with costly decisions and delays to the works to determine correction measures and whether the work completed meets the design intent. This paper shares the knowledge gained over a number of projects the authors’ have been involved in and the methods used to improve the properties of the placed filters taking into account some of the practicalities of having these materials produced and placed in a commercial environment
Keywords: filters, specifications, manufacturing, construction, quality assurance.
Alice Lecocq, Bob Wark, Paul Hurst, Michael Somerford
The justification for dam safety remedial works is often based on an assessment of life safety risk and financial losses defined at a discrete point in time. However these parameters are likely to change over time with demographic growth, land and industrial development. The Water Corporation has a number of dams upstream of major growth areas and an understanding of the future direct and indirect economic consequences of dam failure are required in order to define the change in risk profile over time.
This paper outlines the study framework adopted by the Water Corporation to review its capital expenditure on its remedial works programme. Dam failure consequence assessments for Wellington, Serpentine and Samson Brook Dams are presented and the paper describes the methodology adopted to forecast the likely development within the inundation areas. A framework to consistently estimate future changes to life safety and economic consequences is also presented.
Keywords: demographic growth, land and industry development, monetary assessment, future trends, consequence assessment.
Anurag Srivastava, David S. Bowles, Sanjay S. Chauhan
DAMRAE is a software tool for performing the event tree risk model computations for dam safety risk analysis. It is being applied by the US Army Corps of Engineers (USACE) and undergoing continued development and testing at Utah State University. DAMRAE is designed to overcome the limitations of existing business risk analysis software. It includes a generalized algorithm for constructing and calculating event trees. A generic project framework provides functionality for considering risk reduction alternatives or a staged implementation of risk reduction measures including obtaining estimates of their cost effectiveness of risk reduction. Evaluations against USACE tolerable risk guidelines are made. A flexible capability exists for obtaining tabular and graphical presentations of estimated risks at different levels of detail.
This paper provides an overview of the structure and capabilities of DAMRAE. It also includes an example screenshots to illustrate its capabilities. Plans for future improvements are summarized.
Keywords: Dam Safety Risk Assessment, Event Tree Analysis, Risk Reduction Measures.
Alice Lecocq, David Brett, Mike Rankin
Tailings Dams class amongst the world’s largest man made structures. They are interactive structures that evolve over time, with tailings discharge, water management, embankment raising and finally closure and abandonment. Understanding of the design, the impact of operations and regular, committed surveillance is essential to ensure the safety and performance of a tailings dam. Dam Safety Management Plans should be developed to optimise these parameters. These plans should include Operation, Maintenance and Surveillance (OMS) manuals, emergency response plans and monitoring databases. They should be managed by the mine management and implemented by the operations personnel.
The tailings dam operators are the key to a successful dam safety management program. It is imperative that the tailings dam management and operators appreciate the risks inherent with the facility, their role and their responsibilities. They also need to have an appropriate understanding of the tailings dam design features, failure modes and safety triggers. With training it is expected that personnel will be better able to recognise and act on safety issues arising.
The paper presents case histories of tailings dam failures due to poor operation and management and outlines the operational requirements and risks inherent with tailings dams. The paper discusses the training approach and criteria to be adopted, and describes a training course developed by the authors for mine management and operators. The paper examines the feedback collected from the courses held at several mines. A model to successfully implement a surveillance program with the involvement and leadership of the operators is proposed.
Keywords: TSF failures, surveillance program, OMS manuals, training of personnel.
Australia’s prosperity is closely linked to the development of mining. Tailings production has always been associated with mining and acceptable management strategies of tailings have progressively developed to meet ever changing community expectations. In the late 1800’s, tailings were typically dumped into streams or onto land as mullock heaps, resulting in severe pollution. Practices gradually changed so that by the 1920’s tailings were often held in dams or ponds. However failures were common with slugs of slimes and contaminants moving down watercourses. For the purpose of protecting life and property, States started regulation of the management of tailings under various dam safety umbrellas in the late 1980’s. In 1995, Queensland, in consultation with stakeholders, produced tailings management guidelines, which enunciated good tailings management principles. Later guidelines have incorporated many of these principles. In 2002, the regulation of tailings disposal in Queensland moved into the Environment and Resource Management framework, where the emphasis is on obtaining a sustainable environment. Emerging practices are seeking better ways of incorporating mine tailings into the environment with minimal impact. Backfilling of mine workings, integration of mine waste facilities and beneficial use are some of the methods now used for tailings disposal. This paper looks at the historical management of tailings, the evolving regulatory framework, and the emerging practices for protecting the environment while allowing for development that improves the total quality of life, both now and in the future, in a way that maintains the ecological processes on which life depends.
Keywords: Dams, Tailings, TSF, Community, River Pollution, Cleanup, Risk, Mining