Steven 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.
Leonard A McDonald and Chi Fai Wan
A risk assessment has been undertaken as part of a comprehensive review of the safety of Hume Dam. Use of risk assessment techniques, to assist in evaluating the safety of existing dams, is a relatively recent trend. Hume Dam was a particularly challenging subject for the application of risk assessment techniques at their present stage of development. The challenge lay in the number and diversity of dam elements to be analysed, in the number and complexity of the potential failure modes and in the fact that there were significant safety issues under normal operating conditions.
This paper outlines some of the key lessons learned from that phase of the risk assessment that was concerned with estimating the chance of dam failure. Some of the issues discussed have not previously been addressed in the literature and some demonstrate a clear need for improved analysis procedures.
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.
Alkali-aggregate reaction (AAR) is a potentially deleterious process in concrete containing reactive aggregates, and can lead to varying degrees of cracking in structures, and differential movement and misalignment of concrete elements and mechanical installations. The rehabilitation of affected structures would require information on the extent of current damage and possibility of on-going damage that could be caused by AAR.
Information on the characterisation of concrete components of an AAR-affected dam and estimation of their future potential for further expansion and cracking are provided and repair options discussed in this paper.
M Scuero and Gabriella L Vaschetti
The use of watertight synthetic geomembranes as waterproofing and protection elements for all types of dams started in Europe in the late 1950s and has since been widely applied all over the world as long term repair measure, or as the only element providing watertightness since the design and construction stage.
David S. Bowles, Andrew M. Parsons, Loren R. Anderson and Terry F. Glover
This paper summarises the Portfolio Risk Assessment (PRA) process that was implemented for SA Water’s 17 large dams, the information obtained from the PRA, and its use by SA Water. The PRA was designed to provide a baseline assessment of the existing dams and an initial prioritisation of future investigations and possible risk reduction measures. The PRA comprised a reconnaissance-level engineering assessment and risk assessment. These assessments were performed for floods, earthquakes, and static loading. Various structural and non-structural risk reduction measures were developed and evaluated. Information from the PRA can be used to provide inputs to capital budgeting, due diligence and liability evaluations, contingency planning and business criticality assessment, evaluation of loss financing and insurance programs, and a firm basis for monitoring and surveillance, operations and maintenance, and emergency preparedness planning.