Robert Shelton, Jako Abrie, Matt Wansbone
The Mahinerangi dam – arguably the most valuable in Trustpower’s portfolio of 47 large dams – is over 80 years old and needs a plan of work to confirm it meets current design standards.
The dam was completed in 1931, subsequently raised in 1944-1946, and strengthened with steel tendon anchors in 1961.
A comprehensive safety review (CSR) in 2007 noted a potential deficiency in the fully grouted anchors and a program of work commenced to re-evaluate the overall stability of the dam.
A potential failure mode assessment revealed that the dam may need upgrading to meet the criteria for maximum design earthquake (MDE). Areas of uncertainty were identified and a significant programme of survey, geological mapping, concrete testing and site specific seismic assessments have been carried out to reduce risk and uncertainty in design.
The paper discusses the dam’s history, current condition, and describes the ongoing programme of work planned to extend the life of the dam for another 80+ years.
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Now showing 1-12 of 46 2980:
Russell Mills PhD,Rebecca Freeman, Malcolm Barker
The global mining industry lives with the risk of catastrophic events such as water storage or tailings dam failures as part of its daily operations, and has developed a number of approaches to enable mine management to understand the nature of the risks and the ways in which they are being managed. One such approach involves the use of bowties for the understanding of the hazards and risks. Building from bowties, the second approach involves the selection and management of controls critical to the prevention or mitigation of the catastrophic event. The Australian mining industry is a world leader in this regard and the purpose of this paper is to illustrate how bowties are constructed, how risks can be semi-quantitatively estimated, how critical controls are selected and managed, and how, if all this is done well, risks can be demonstrated to be as low as reasonably practicable (ALARP).
This paper sets out key themes and presents an example for a tailings dam failure to illustrate the role of bowties and critical controls in management of catastrophic events. It will also highlight the role of bowties in the anticipated introduction of a Safety Case approach to dam risk management. Bowties provide a useful tool for the transfer of risk management knowledge from the designer, to allow dam owner / operators to better understand their risks and to recognise the link between design and operational controls and how they are used to manage those risks to ALARP.
Alan P. Jeary, James O’Grady, Thomas Winant
Mainmark are introducing the STRAAM system of full scale non-destructive testing for dams into Australia and New Zealand. Advances in measuring extremely low amplitude vibrations combined with methods for extracting the unique dynamic signature have now enabled the rapid measurement of the response of earthen and concrete dams. This ability allows the quick calibration of Finite Element Models that can be used to accurately assess the strength of a dam. Furthermore, this information allows dam owners to efficiently track changes in the capacity of their dams due to aging, earthquake or flood activity through changes in the dynamic.
The STRAAM system measures the vibration of the dam structure to establish the natural frequencies, mode shapes and associated damping ratios of the dam. The field measurements are correlated with a three-dimensional finite element model to fine tune the effects of abutments and foundations on the three dimensional model. Because of the sensitivity of the instrumentation and the novelty of the analysis techniques, the information available to dam managers allows information-based decisions to be made in a way that optimizes the financial implications. In addition, the techniques are non-invasive and non- destructive and they give additional information about the connectivity of the dam with the surrounding terrain, and whether that connectivity is compromised by water seepage.
This paper discusses the results obtained from field measurements from four dams located in Switzerland, USA and Scotland.
David Piccolo, Gareth Swarbrick, Garry Mostyn, Bruce Hutchison, Rodd Brinkmann
Hillgrove Resources owns and operates Kanmantoo copper mine some 44 km southeast of Adelaide.
An important feature of the mine is its tailings storage facility (TSF) which is fully lined with HDPE, and double lined at the base, fully under drained, has a secondary underdrainage system for leak detection and a multi-staged centralised decant system. This onerous design of the TSF was developed in consultation with DMITRE between 2007 and 2010 amid concerns of groundwater protection and effective water management.
The Authors were approached in 2010, following construction of the initial stage of the TSF, and charged with developing the design to increase storage from 13 to 20 million tonnes, as well as optimising the design and construction of future stages.
This paper presents the more interesting aspects of the design and construction optimisation between 2010 and 2016 including:
The design and construction approaches have been scrutinised and accepted by regulatory authorities, and implemented by the mine operator over a period of 6 years. The paper includes lessons learnt during the implementation process.
Woodrow Lee Fields
Although flooding can lead to many types of severe consequences, the primary objective of the US Army Corps of Engineers (USACE) dam and levee safety programs are to manage risk to the public who rely on those structures to keep them reasonably safe from flooding. Thus, reducing the risk associated with loss of life is paramount. This paper discusses new methods that have been developed for estimating life loss with uncertainty from flood events.
HEC-LifeSim is a dynamic simulation system for estimating life loss with the fundamental intent to simulate population redistribution during an evacuation in conjunction with flood wave propagation. The population redistribution process has been revised from the ground up as an agent based model. In addition to the agent based model, uncertainty analysis has been enhanced. Through Monte Carlo sampling, the natural variability of warning and mobilization timing and likelihood of fatality varies delivering a range of potential life loss from a hazard. Knowledge uncertainty about parameters, such as warning issuance time, can also be defined. To accommodate the new HEC-LifeSim computation engine, an innovative GIS interface has been developed to quickly summarize and animate results. The methods that are discussed in the following provide new tools to estimate life loss and educate local authorities.
Amanda Ament, Thomas Ewing, Frank Nitzsche
The automatic operating buoyancy type spillway gates at Lenthall Dam did not operate properly since installation. This paper discusses the problems encountered, the investigation conducted using computational fluid dynamics to quantify the problems and develop solutions. It describes the design of the modifications to the gate and flow regime and results after construction.