Ensuring compliance with the Regulator’s requirements is a cornerstone consideration for any water corporation in planning its risk minimisation strategies against dam failure. With the increased focus on due diligence and corporate governance however, there are emerging themes that are of equal importance for a water corporation in planning protections against its core risks to dam safety.
These considerations include:
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Now showing 1-12 of 59 2970:
Michael Somerford, Alex Gower
The Water Corporation is the principal dam owner in Western Australian with a portfolio of 95 dams. In the absence of dam safety legislation in Western Australia the Corporation has adopted a policy of self regulation. This paper presents how the Corporation’s dam safety policy has been implemented with respect to dam instrumentation and monitoring. It includes a summary of the type of instruments used and experiences with automated data collection systems. The paper concludes that the Corporation does not see a need for a dam instrumentation guideline, however a document summarising current Australian practices and experiences would be of value.
C Lake and J Walker
Meridian Energy is the owner and operator of a chain of hydro dams on the Waitaki River in the
South Island of NZ. It operates a Dam Safety Assurance Programme which reflects current best
practice; consequently it has focused primarily on managing civil dam assets. Advances in plant control technology have allowed de-manning of our power stations, dams and canals through centralised control. The safety of our hydraulic structures is increasingly reliant on the performance of Dam Safety Critical Plant (DSCP) – those items of plant (eg water level monitoring, gates, their power and control systems, and sump pumps) which are required to operate automatically, or under operator control, to assure safety of the hydraulic structures in all reasonably foreseeable circumstances.
Recent dam safety reviews have highlighted that the specification and testing of our DSCP is based on the application of ‘rules of thumb’ which have been established through engineering practice (eg. “monthly tests”, “third level of protection”, “backup power sources”, “triple voted floats”). The
adequacy of these engineering practices is difficult to defend as they are not based on published
criteria. The realisation that such rules may not be relevant to the increased demand on, and complexity of, DSCP led us to ask “Which belts and braces do we really need?” The current NZSOLD (2000) and ANCOLD (2003) Dam Safety guidelines give little guidance regarding specific criteria for the design and operation of DSCP.
Meridian has identified the use of Functional Safety standards (from the Process industry, defined in IEC 61511) as a tool which can be applied to the dams industry to review the risks to the hydraulic structures, the demands on the DSCP, and utilise corporate “tolerable risk” definitions to establish the reliability requirements (Safety Integrity Levels) of each protection, and determine lifecycle criteria for the design, operation, testing, maintenance, and review of those protections.
This paper outlines the background to identifying Functional Safety as a suitable tool for this purpose, and the practical application of Functional Safety Analysis to Meridian’s DSCP.
Peter J Burgess, Delfa Sarabia, John Small, H. G. Poulos and Jayanta Sinha
The assessment of settlement behaviour of clay core rock fill dams has always been a challenge for dam designers and geotechnical engineers. The method of construction and the material properties of the clay and rock fill materials used in the dam construction have a significant influence on the inter-zonal interaction and the load transfer that occurs within the dam. At times this load transfer can lead to excessive differential and total settlements. The paper presents a case study of a major dam that experienced large settlements during and after construction. An elaborate analysis has been carried out by modelling the sequences of construction by using a finite element program (PLAXIS).
The paper describes the influence of the degree of compaction and moisture control on non-linear deformation characteristics of clay core. High vertical strains in the wet placed region of the core and low strains in the dry placed regions were analysed for possible shear development between the core and shell. The rock fill for the dam embankment consists of quartzite, metasiltstone and phyllite material. These materials have apparently undergone deformation with increasing height of the dam due to softening and crushing as saturation of the embankment took place. The effect of soil consolidation and strength gains have been considered in the analysis and are discussed. The settlement behaviour of the dam including these effects has been analysed, and compared with the historical post-construction settlements.
This paper is intended to provide valuable information for dam engineers handling clay core rock fill dams – especially where there is excessive settlement of the core.
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.
Malcolm Barker, Barry Vivian and David S. Bowles
Ross River Dam is located approximately 15 km upstream of Townsville and provides a dual role of water supply and flood mitigation. The dam comprises a 39.6m long concrete overflow spillway flanked by a central core rockfill embankment of 300 m in length with a 7,620 m long left bank earth fill embankment, which has inadequate internal filter zones for piping protection. Since completion, design rainfall predictions for the area have doubled, technical data has changed and so, too, have dam safety standards. Dam safety evaluations during 2000-2002 showed that the dam required upgrading in order to bring it up to international standards. As an interim measure, the spillway was cut down by 3.6m.
Upgrade design works were then completed using risk-based design criteria to validate the design, and construction is in progress. The upgrade works comprise spillway anchoring, installation of three radial gates on the spillway, stilling basin modifications, embankment filter protection, and dam crest raising.
This paper presents the options considered, the method of reliability analysis, and how the results influenced the spillway system design and overall risk evaluation for the upgrade design.