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The Eildon Dam Improvement Project is being undertaken by Goulburn-Murray Water as part of its dam improvement program that includes an upgrade of the existing Lake Eildon spillway that passes through the left abutment of the dam. The main components of the spillway are a gated concrete gravity overflow section that is 33 m high and 60 m wide, a 435 m long low gradient spillway chute and a hydraulic jump stilling basin.
The spillway was originally designed, including a physical model, in the 1950s to pass a maximum discharge of 3,400 m3/s with a maximum reservoir head of 9.0 m above the spillway crest. This can be compared with the 2003 flood hydrology and flood routing studies that result in a PMF discharge of 6,900 m3/s and a maximum reservoir head of 14.1 m above the spillway crest.
A new physical hydraulic model study was carried out over 2003-2004 as part of the investigations by the Eildon Alliance for the Project. The model was tested with discharges up to and exceeding the upgraded PMF. Very turbulent conditions were observed at discharges exceeding the original design discharge including the formation, build-up and collapse of large diameter vortices in flow over the spillway crest and overflow section. The vortex phenomena resulted in the intermittent formation of high waves and very high transient pressure loadings at the downstream toe of the overflow section and extending to the upstream section of the spillway chute. The paper discusses some scaling issues, presents some of the salient results of the study and discusses their application to the 2003-2004 design of structural modifications for the spillway.
The paper includes a discussion and comparison of the 1950’s model study with the 2003-2004 study. The magnitude of the vortex phenomena could not be predicted from the previous studies, and it is recommended that investigations for upgrades of similar works that involve large increases in design discharges include detail examination of vortex phenomena.

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2004 Papers

2004 – HYDRAULIC MODEL STUDY FOR EILDON DAM IMPROVEMENT PROJECT
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The Eildon Dam Improvement Project is being undertaken by Goulburn-Murray Water as part of its dam improvement program that includes an upgrade of the existing Lake Eildon spillway that passes through the left abutment of the dam. The main components of the spillway are a gated concrete gravity overflow section that is 33 m high and 60 m wide, a 435 m long low gradient spillway chute and a hydraulic jump stilling basin.
The spillway was originally designed, including a physical model, in the 1950s to pass a maximum discharge of 3,400 m3/s with a maximum reservoir head of 9.0 m above the spillway crest. This can be compared with the 2003 flood hydrology and flood routing studies that result in a PMF discharge of 6,900 m3/s and a maximum reservoir head of 14.1 m above the spillway crest.
A new physical hydraulic model study was carried out over 2003-2004 as part of the investigations by the Eildon Alliance for the Project. The model was tested with discharges up to and exceeding the upgraded PMF. Very turbulent conditions were observed at discharges exceeding the original design discharge including the formation, build-up and collapse of large diameter vortices in flow over the spillway crest and overflow section. The vortex phenomena resulted in the intermittent formation of high waves and very high transient pressure loadings at the downstream toe of the overflow section and extending to the upstream section of the spillway chute. The paper discusses some scaling issues, presents some of the salient results of the study and discusses their application to the 2003-2004 design of structural modifications for the spillway.
The paper includes a discussion and comparison of the 1950’s model study with the 2003-2004 study. The magnitude of the vortex phenomena could not be predicted from the previous studies, and it is recommended that investigations for upgrades of similar works that involve large increases in design discharges include detail examination of vortex phenomena.
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2004 Papers

2004 – Hydraulic Model Study For Eildon Dam Improvement Project
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Ian Hampton, Dr Mohand Amghar and James Willey

The Eildon Dam Improvement Project is being undertaken by Goulburn-Murray Water as part of its dam improvement program that includes an upgrade of the existing Lake Eildon spillway that passes through the left abutment of the dam. The main components of the spillway are a gated concrete gravity overflow section that is 33 m high and 60 m wide, a 435 m long low gradient spillway chute and a hydraulic jump stilling basin.

The spillway was originally designed, including a physical model, in the 1950s to pass a maximum discharge of 3,400 m3/s with a maximum reservoir head of 9.0 m above the spillway crest. This can be compared with the 2003 flood hydrology and flood routing studies that result in a PMF discharge of 6,900 m3/s and a maximum reservoir head of 14.1 m above the spillway crest.
A new physical hydraulic model study was carried out over 2003-2004 as part of the investigations by the Eildon Alliance for the Project. The model was tested with discharges up to and exceeding the upgraded PMF. Very turbulent conditions were observed at discharges exceeding the original design discharge including the formation, build-up and collapse of large diameter vortices in flow over the spillway crest and overflow section. The vortex phenomena resulted in the intermittent formation of high waves and very high transient pressure loadings at the downstream toe of the overflow section and extending to the upstream section of the spillway chute. The paper discusses some scaling issues, presents some of the salient results of the study and discusses their application to the 2003-2004 design of structural modifications for the spillway.

The paper includes a discussion and comparison of the 1950’s model study with the 2003-2004 study. The magnitude of the vortex phenomena could not be predicted from the previous studies, and it is recommended that investigations for upgrades of similar works that involve large increases in design discharges include detail examination of vortex phenomena.
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2015 Papers

2015 – Efficient and cost-effective modelling and analysis of hydraulic structures using CFD
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Thomas Ewing, Marius Jonker & James Willey

The use of Computational Fluid Dynamics (CFD) modelling techniques is gaining broad acceptance in the dams industry as an important design tool for hydraulic structures. This is particularly so in the earlier stages of analysis and design where the construction of physical models would be prohibitive on the basis of cost and time. Current CFD techniques allow users to produce a rapid evaluation of the existing conditions, which when coupled with the ability to quickly test an array of potential scenarios, enables the incorporation of innovative design solutions that may otherwise not have been considered during the design selection process prior to the advent of CFD capabilities.

Details of a recent case study are presented to illustrate the broad capabilities and benefits of CFD modelling techniques and their application in engineering analysis and design. The case study involves modelling of the Somerset Dam, a 50 m high concrete gravity dam with a gated overflow spillway including overtopping of the spillway bridge, gates and complex flow conditions in the abutment sections, which individually and collectively could not be accurately analysed with the traditional, simplified methods. The CFD study enabled an understanding of the hydraulic behaviour including discharge efficiency, jet impact loads on the gates and gate operating equipment and bridge structure; extent of potential erosion as a result of jet impingement on the abutments; loads on sluices and behaviour of the stilling basin. In addition to being a very large and complex model, the modelling involved several novel technical aspects.
The case study clearly highlights the benefits of the CFD modelling in understanding the complex hydraulic conditions and delivering cost effective solutions.
Keywords: Computational Fluid Dynamics, Somerset Dam.
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2017 Papers

2017 – Construction Flood Risk Strategies for Dam Upgrades
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Colleen Baker, Sean Ladiges, Peter Buchanan, James Willey, Malcolm Barker

Dam Owners and Designers are often posed with the question “what is an acceptable flood risk to adopt during the construction of dam upgrade works?” Both the current ANCOLD Guidelines on Acceptable Flood Capacity (2000) and the draft Guidelines on Acceptable Flood Capacity (2016) provide guidance on the acceptability of flood risk during the construction phase. The overarching principle in both the current and draft documents is that the dam safety risk should be no greater than prior to the works, unless it can be shown that this cannot reasonably be achieved.Typically with dam upgrade projects it is not feasible to take reservoirs off-line during upgrade works, with commercial and societal considerations taking precedent. It is therefore often necessary to operate the reservoir at normal levels or with only limited drawdown. The implementation of measures to maintain the risk at or below that of the pre-upgraded dam can have significant financial and program impacts on projects, such as through the construction of elaborate cofferdam arrangements and/or staging of works. This is particularly the case where upgrade works involve modifications to the dam’s spillway.The use of risk assessment has provided a reasonable basis for evaluating the existing and incremental risks associated with the works, such as the requirement for implementation of critical construction works during periods where floods are less likely, in order to justify the As Low As Reasonably Practicable (ALARP) position. This paper explores the ANCOLD guidelines addressing flood risk, and compares against international practice. The paper also presents a number of case studies of construction flood risk mitigation adopted for dam upgrades on some of Australia’s High and Extreme consequence dams, as well as international examples. The case studies demonstrate a range of construction approaches which enable compliance with the ANCOLD Acceptable Flood Capacity guidelines
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2018 Papers

2018 – Spillway stilling Basin Linings Design using Physical Hydraulic Modelling and DES CFD Modelling: Application of New Technologies
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Shayan Maleki, James Willey, James Apostolidis, and Virgilio Fiorotto

The evaluation of the maximum instantaneous uplift force produced by turbulent pressure fluctuations plays a key role in designing concrete slab protection in spillway chutes and stilling basins. Recent incidents involving damage to chute linings have highlighted the significance of this issue. To evaluate the stability of spillway stilling basin slabs, it is necessary to determine the statistical structure of the turbulent pressure fluctuations in the spillway chute and stilling basin. This can be defined by an extensive experimental work with a scale Physical Hydraulic Model (PHM). This exercise can be prohibitively expensive in terms of time and cost and it is proposed that the use of Computational Fluid Dynamics (CFD) in this application could become a cost effective alternative. A new approach using Detached Eddy Simulation (DES) was applied to the case of a scale physical hydraulic model representing a real-world prototype and the results of the simulation were compared with the direct laboratory measurements. Here the forces and pressures acting on the slabs are evaluated using both CFD and physical hydraulic modelling results. In conclusion, some considerations on the design of slabs with unsealed joints are reported and discussed.
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2013 Papers

2013 – Case studies of foundation grouting using the GIN method at the enlarged Cotter Dam
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Sean Ladiges, James Willey, Matthew Norbert and Andrew Barclay

The Enlarged Cotter Dam (ECD) Project, located in ACT, consisted of the construction of a new 87 m high roller-compacted concrete (RCC) dam and two central core zoned earth and rockfill saddle dams up to 23 m high on the low points of a ridge to the south-west of the Main Dam. The Main Dam is the highest RCC dam constructed in Australia.
A continuous single-line grout curtain with a total length of 1.2 km was constructed across the full extent of the Main Dam and the two saddle dams with the aim of reducing future seepage losses through the dam foundations. The grouting processes were similar for the main and saddle dams respectively, however the grouting of the Main Dam and saddle dams was carried out as two separate contract packages by different subcontractors. As such, the project provides a unique opportunity to undertake a comparison of the foundation conditions and control equipment and outcomes from the two packages of work. The foundation conditions were different at each of the three dams, with varying geology across the site.
The saddle dam grouting was completed in 2010, with the grouting carried out at the base of the core trench prior to construction of the embankments, while the grouting of the Main Dam was conducted in 2012-13, with most of the grouting works executed from the drainage gallery within the constructed dam.
Consistent throughout construction of the ECD grout curtain was a similar philosophy of real-time computer control, the use of Grout Intensity Number (GIN) parameters, water pressure testing, desirable grout mix properties and the avoidance of damage to the foundations. There were a number of key differences in the grouting process for the saddle dams and Main Dam; these include the ground conditions, the pumping control systems used, the GIN parameters adopted and the grout materials and mixes selected.
This paper provides a critical evaluation of the two grouting programmes, an assessment of the effectiveness of the grouting, comments on tools and methods used, and proposes a set of recommendations for curtain grouting over a range of ground conditions based on lessons learnt during the project.
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2008 Papers

2008 – Risk assessment in spillway remedial works design and construction and monitoring at Googong Dam
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James Willey, Malcolm Barker, Javad Tabatabaei

Abstract: During successive flood events from the end of construction of Googong Dam in 1978 through to the late 1980s, erosion of in excess of 5,000 m³ of rock occurred in the partially unlined section at the downstream end of the spillway channel. Remedial works were undertaken in stages during the 1980s to stabilise the eroded chute and limit further erosion. A project is currently underway as part of the Bulk Water Alliance to construct remedial works in the spillway to repair erosion damage and increase the spillway capacity to safely pass the current estimate of the Probable Maximum Flood. The design was undertaken by GHD Pty Ltd as part of a separate engagement prior to the formation of the Alliance.

The recent work involved a review of the historical performance and prediction of future performance of the structure. A process involving the development and comparison of options and ultimately the detailed design of the preferred arrangement followed, including refinement and validation using a physical hydraulic model study.

This paper presents risk assessment techniques used throughout the project on a range of tasks including prediction of future spillway erosion damage and comparison of spillway remedial works options, assessment of construction flood risk and definition of instrumentation requirements for the dam and associated structures.

Keywords: risk assessment, remedial works, spillway erosion, rock erosion, construction risk, instrumentation.
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2010 Papers

2010 – Googong Dam Spillway Upgrade – Construction Challenges and Alliance Framework
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Ben Greentree, David Bamforth, Matthew O’Rourke and James Willey

A series of relatively small floods occurring between end of construction in 1978 and late 1980s caused extensive and dramatic rock erosion to the very steep unlined section of the Googong Dam spillway. Following a review of hydraulic performance at larger floods, the spillway’s future erosion potential was evaluated and it became clear that extensive remedial work was required. A detailed design was developed comprising the retro-fitting of a full concrete-lined chute, the raising and extension of the spillway chute walls, strengthening of the upstream training walls and excavation of a large plunge pool. The Googong Dam has an ANCOLD hazard rating of ‘extreme’ because of its location upstream of Queanbeyan and Canberra.
In early 2008, the Bulk Water Alliance (BWA), comprising ACTEW Corporation Ltd, (in cooperation with ActewAGL) (the Owner), GHD Pty Ltd (the Designer) and Abigroup Contractors Pty Ltd in joint venture with John Holland Pty Ltd (the Constructors) was formed to deliver a package of water security projects for the ACT, one of which is the Googong Dam Spillway Upgrade.
After preparation of a construction methodology and target outturn cost (TOC), the project was approved by the Actew Board and construction commenced in February 2009. Completion is due in late 2010. A number of significant geotechnical, structural and logistical challenges were encountered during construction, resulting in major changes to the construction methodology necessitating design changes. The changes were incorporated within the original TOC, without instigating scope change contractual claims and while still maintaining spillway functionality in line with Owner operational requirements.
This paper presents delivery phase challenges that necessitated construction methodology and design changes to achieve best for project outcomes; how these challenges were overcome through genuine innovation reliant on a collaborative effort by all the Alliance partners; and how the contractual framework of the Alliance was essential for the change management process to be successful.
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Search Results: “” — Page 1

Shayan Maleki, James Willey, James Apostolidis, and Virgilio Fiorotto