2008 – It’s all in the planning – replacement of a valve under full reservoir head
Stuart Richardson, Peter Liepkalns, Rod Mauger
Abstract: Operations and maintenance of large dams can be complex and potentially high risk. Even on a relatively new dam like Dartmouth, Goulburn-Murray Water is regularly presented with maintenance tasks which are made very difficult because access for maintenance may not have been considered during the original design and construction of the dam.
Goulburn-Murray Water recently completed a change over of a 200mm cast iron gate valve at Dartmouth, not in itself a complex or high risk maintenance task. What made this task challenging was that the valve was subject to full reservoir head (up to 180m) with no means of isolation.
$15.00
Related products
-
$15.00
Papers 2008
2008 – Towards responsible management of tailings facilities
Learn moreElizabeth Gardiner, Len Murray, David Gladwin
Abstract: The Mining Association of Canada has worked over the past 12 years to improve the management of tailings facilities. This effort began out of a realization that tailings present a major business risk to the mining industry, and that a series of major tailings failures around the world in the 1990’s were fundamentally indicative of need for improved care and management practices by tailings dam and facility owners and operators. MAC established and continues to sponsor the Tailings Working Group, which has assisted in development and publication of a three-volume set of guides to improve tailings management:
•“A Guide to the Management of Tailings Facilities”, initially published in 1998, updated edition published in 2008;
•“Developing an Operation, Maintenance and Surveillance Manual for Tailings and Water Management Facilities”, published in 2003; and
•“A Guide to Audit and Assessment of Tailings Facility Management”, published in 2008.
The three guides provide a strong message that the key to safe and environmentally responsible management of tailings is consistent application of sound engineering capability within an effective management framework.The documents are almost directly applicable to all forms of dams and are widely used for water dams. Also, because the documents are available in Spanish and French they have found wide use in International projects.
A brief comparison with published ANCOLD guidelines is provided.
Keywords: Management of tailings facilities and water dams, Operation, Maintenance and Surveillance, Auditing, risk, safety, guides
Learn more -
$15.00
Papers 2008
2008 – Seismic hazard assessment at Hinze Dam
Learn morePaul Somerville, Gary Gibson
Abstract: This paper describes current methods for seismic hazard analysis and their application at Hinze Dam. Although Southeastern Queensland has experienced significant earthquakes in historical time, none of them are known to have caused surface rupture, and no active faults that could be used to represent earthquake sources have been identified in the region that surrounds the site. Under these conditions, we must estimate the seismic potential of the region using historical seismicity. Two alternative approaches to modelling future earthquake occurrence based on historical seismicity have been used. The first approach is based on the AUS5 source model of ES&S (2005), which uses geological criteria to identify zones of uniform seismic potential, and then uses historical seismicity to characterize the seismic potential of each zone. The second approach, developed by Hall et al. (2007) at Risk Frontiers, is based on the spatial smoothing of historical seismicity without identifying discrete source zones. Previous work by ES&S has shown that the attenuation of strong ground motion in Southeastern Australia is fairly well represented by ground motion models developed using strong motion data from western North America. The recently developed NGA ground motion models based mainly on data from Western North America represent the local site conditions using Vs30, the shear wave velocity averaged over the top 30 metres at the site. This provides a significant advantage over previous models, which were for broad site categories such as rock or soil, and did not provide for the use of more site-specific information. The left abutment, lower tower and valley section foundation at Hinze Dam are characterized by hard unweathered rocks with shear wave velocity of 2.0 km/sec estimated from P wave velocity measurements. The right abutment of the main embankment and the saddle embankment foundation consist of extremely weathered rock, with shear wave velocity of 0.45 km/sec estimated from P wave velocity measurements. This causes the ground motion response spectra estimated for the right abutment and neighbouring foundation components to be significantly larger than for the left abutment and neighbouring foundation components, by factors of 1.4, 2.0 and 2.3 for periods of 0 (PGA), 0.5 sec and 1 sec respectively.
Keywords: seismic hazard analysis.
Learn more -
$15.00
Papers 2008
2008 – An overview of risk assessment tools for US Army Corps of Engineers dams
Learn moreDavid M Schaaf, Jeffrey A Schaefer, Rick W Schultz, Jason T Needham
Abstract: As one of the main federal agencies with responsibility to build, operate, and maintain large dams in the United States, the US Army Corps of Engineers (USACE) is developing a risk based framework to better manage their portfolio of 600+ dams in terms of risk management and prioritization of funding. A key element to this effort is the development of risk-based analytical tools to evaluate primary features for applicable failure modes. These are used in conjunction with loading and consequence modules to assess the overall risk associated with the dam in terms of lives and economic damages. The focus of this paper is on the engineering analysis modules used to generate fragility curves for dam features.
The analysis modules are broken into three main categories by engineering discipline: geotechnical, structural, and mechanical/electrical. The risk based assessment tools associated with geotechnical failure modes include Seepage & Piping, Embankment Stability, Seismic Performance, and Erosion of Unlined Spillways. The structural assessment tools include Concrete Monolith Stability, Spillway Gates, Scour of Concrete Lined Spillways, Spillway Training Wall Stability, Performance of Pipes through Dams, Hydropower Superstructures and Intake Towers. The mechanical and electrical are primarily focused on the performance of machinery used to operate dam gates.
This paper gives a broad overview of the main characteristics and methods used for each of these analysis tools. Some of the modules use historical performance to establish failure rates, while others are more analytically based. The context of each within the framework of the overall risk assessment effort of USACE dams is covered.
Keywords: risk based analytical tools, fragility curves, risk assessment, US. Army Corps of Engineers, portfolio, dams.
Learn more -
$15.00
Papers 2008
2008 – Improving confidence in computational fluid dynamics for spillways
Learn moreRichard John Kenny
Abstract: Physical hydraulic models have traditionally provided the input to spillway design.
However, the application of Computational Fluid Dynamics (CFD) is increasing in popularity.
The reliability of CFD depends on several complex issues including the physics of the flow regime, the mathematical formulae describing the fluid flow and the solution method. CFD reliability should be confirmed for each particular application, including ogee spillways (common discharge structures on dams).A literature review has been undertaken to determine validation techniques and the reliability of CFD related to ogee spillways. There is a great deal of information available about the aeronautical, marine, automotive and mining industries but relatively little available about ogee spillways. The degree of validation for ogee spillways was found to vary significantly and raises the question of whether better validation can be achieved. Better validation may improve confidence in CFD techniques.
A project has been undertaken through Queensland University of Technology to model a prototype scale notional 2D ogee spillway using FLUENT CFD software under steady state conditions. The project tests the sensitivity of the CFD results to various parameters. The sensitivity of the inlet mass flow rate was tested for several CFD parameters. The investigation considered:
1.The grid spacing required for geometric convergence;
2.The effect of domain extent on the computational results;
3.The influence of a boundary layer and wall roughness;
4.The importance of the choice of turbulence model; and
5.The impact of inlet turbulence assumptions.
The recommendations of the sensitivity investigations were used for validation against the United States Army Corp of Engineers (USACE) design data.
Excellent agreement was found between the CFD predictions and the USACE values.
Keywords: Computational fluid dynamics (CFD), dam, flood routing, fluent, Navier-Stokes equations, Numerical/computational modelling, Ogee spillway crest, physical model, turbulence.
Learn more -
$15.00
Papers 2008
2008 – Flooding of the Glenmaggie Dam and Cowwarr Weir storages-June 2007
Learn moreMark Hore, Joseph Matthews
Abstract: Substantial flooding occurred in the Gippsland region in late June 2007, following the severe bushfires experienced during the previous summer. Major damage was sustained to the regions infrastructure, which included the gated storages at Glenmaggie Dam and Cowwarr Weir, located in the neighbouring Macalister and Thomson river catchments respectively. The flood event at Glenmaggie Dam produced a record peak inflow of well over 250,000 ML/day, which was more than twice the previous record.
The magnitude and intensity of the flood event created a number of issues for the staff at Southern Rural Water (SRW), who are engaged in the safe operation of the facilities. The event tested the organisations emergency management systems and the ability of the organisation to effectively manage events at multiple sites. Some of challenges faced included: a rapid rise in storage volumes; the loss of upstream warning gauges; the accumulation of large volumes of debris; the development of suitable release strategies and the communication and engagement with the local community.
The event caused a significant amount of damage to key infrastructure at both sites, with the Cowwarr Weir storage being the worst affected. A number of high priority projects have been completed since the event, with spending to date totalling $3 million. The unusual nature of the flood event provided the opportunity to review previous flood assessments and to identify deficiencies with elements of the existing infrastructure. Of particular interest was the subsequent hydrology review which provided a comparison with previous modelling assessments. The review included a flood frequency assessment which showed that the magnitude of the Glenmaggie flood was in the order of a 1:200 AEP(Annual Exceedance Probability) event, which was disproportionate to the rainfall event frequency assessed as having a 1:50 AEP, when averaged across the catchment. The aim of the paper is provide a case study for other dam engineers who may be preparing for future flood events in similarly affected catchments.
Keywords: flood, gated storage, dam performance, remedial works.
Learn more