Dr. Mark Locke, Jiri Herza
Gördes Dam is a nickel and cobalt mine tailings dam situated in a seismically active zone in Manisa Province, Western Turkey. The dam is a conventional cross valley earthfill structure with a fully lined storage basin. The starter embankment with a maximum height of 50 m will be raised in downstream lifts to an ultimate height of 90 m. The total storage capacity is 19 million m3. Construction of the starter embankment is planned to commence in late 2012 and the dam will be commissioned in June 2013.
The tailings will be discharged from the dam crest and return water will be collected by a floating decant pump at the opposite site of the storage. Decant water has high calcium sulphate levels and will require treatment before re-use in the plant or release. The tailings contain about 33 % of solids and are classified as high plasticity silts and clays with more than 90 % of particles passing the 0.075 mm sieve.
The dam is founded on a complex formation of altered sedimentary and metamorphic rocks including mudstones, siltstones, limestones and serpentines. The mudstone blocks, the predominant foundation materials, are juxtaposed with siltstones and serpentines via a complex arrangement of faults. Where exposed, the mudstones are highly to completely weathered with a well-developed structure of smooth bedding surfaces leading to anisotropic strength characteristics. Several landslides, likely associated with the anisotropic character of the mudstones, were identified within the area including a significant landslide under the upstream shoulder of the dam.
Mining development in Turkey has a complex legislative environment. There is also standard practice which is not legislated but expected, this can be considerably different to normal design practice in Australia. The Turkish legislation is based on waste management guidelines and may be more appropriate to landfills than large tailings storages. The legislation is very prescriptive in some aspects and silent in others, with little consideration of risk or consequence based design.
This paper discusses the design difficulties associated with the challenging foundation conditions, which have been magnified by the requirements and limitations embedded in the approval documentation and the legislative environment in Turkey. It will also address some of the key differences between the design philosophy in Australia and in Turkey with a focus on the major risk elements of the design.
Keywords: Tailings, Turkey, Liner, HDPE, Nickel laterite
— OR —
Now showing 1-12 of 40 2976:
Sofia Vargas, Robert Wark
Logue Brook Dam, 130 km south east of Perth, was completed in 1963 and comprises a 49 m high main embankment with a crest length of approximately 335 m and the reservoir impounds 24.59 GL of storage. The outlet works comprise an inlet tower, an outlet pipe (DN 1100 mm) and a valve house. Water from the dam is released through a clam shell valve and there is a sluice valve upstream of the clam shell which acts as a scour isolation valve.
Previously Logue Brook Dam supplied water into the Harvey irrigation system by releasing water down the river which was then drawn off downstream and pumped into the piped network. The scheme planning had identified that constructing a pipeline from the dam outlet to connect directly into the piped irrigation system would eliminate the need for pumping as the system could then be gravity fed directly from the dam.
The outlet works upgrade comprised the refurbishment of the Inlet Tower, refurbishment of the Valve House, installation of new valves, environmental release and magnetic flow meters, electrical, communications, SCADA, instrumentation and security upgrades.
This paper describes the diving inspection and above water inspections of the inlet tower, refurbishment of the existing installation, challenges of the design, adopted solutions, connection to the Harvey Water pipeline and construction issues. The project represents an interesting case history of improving dam safety standards to current ANCOLD guidelines to provide a modern and safe facility.
Keywords: Outlet works, diving, OH &S Issues, safety, deterioration
Mike Phillips, Kelly Maslin
A spillway upgrade conceptual design and selection process was undertaken to identify options for upgrading the Dartmouth Dam to pass the Probable Maximum Flood (PMF). A number of upgrade options were investigated, including variations of dam raise heights and spillway modifications. One of the options, the piano key weir, was initially developed from the limited available publications on the weir design, and further developed with the use of a 1:60 scale model. The piano key weir, a variation of the labyrinth weir, is a passive spillway that utilises a total weir length several times that of the effective spillway width. For the Dartmouth Dam study, the piano key weir design that was developed consisted of a 7-cycle, 9 m high structure, with a total weir length of nearly 600 m, or more than 6 times the existing effective spillway width of 91 m. The spillway was designed to pass the routed PMF outflow of approximately11,500 m3/s with a head of approximately 11 m.
The piano key weir design was developed using the following analyses:
Initial 1:60 scale physical model of the piano key weir based on published papers on piano key weirs and design manuals for labyrinth weirs;
Structural analysis and weir member sizing using initial physical model results;
Computational Fluid Dynamics (CFD) modelling to improve the hydraulic efficiency of the weir for the range of flows;
Revised 1:60 scale physical model of the piano key weir; and
Confirmation of conceptual structure design.
This paper describes the process of developing the piano key weir option for the Dartmouth Dam spillway and lessons learned.
Keywords: Piano key weir, CFD, spillway, physical model
M C N Taylor, Dr H E Cherrill, S F Croft, S F Eldridge
The Stuart Macaskill Lakes are two raw water storage lakes with a combined storage of approximately 3280 ML supplying Wellington City, New Zealand. The lakes are High Potential Impact Category (PIC) earth embankment dams constructed on terrace gravel deposits adjacent to the Hutt River and located within approximately 20 to 50 metres of the Wellington Fault Deformation Zone. Construction of the lakes began in 1982 and they were commissioned in 1985.
In early 2008, the lake’s owner Greater Wellington Regional Council (GWRC), embarked on a programme to supplement Wellington City’s water supply storage. Whilst that study is ongoing, GWRC engaged Tonkin & Taylor (T&T) to investigate the feasibility of increasing the Stuart Macaskill Lakes capacity as an interim measure.
The feasibility study concluded in late 2009 that the lake dam embankments could be raised by up to 1.3 metres in height to gain an approximate additional 450 ML of water storage. An important finding of that feasibility study has been that the seismic requirements have increased significantly since the construction of the lakes. To address this issue GWRC is currently constructing Stage Two of a two stage construction programme to both raise the lakes and to incorporate seismic resistant features into the lakes.
The primary design features are downstream rock buttressing in the critical areas of the lakes and synthetic lining the inside of the lake embankments. The buttressing works were completed in early 2011 and the lining and crest raising works are due for completion in 2013.
This paper summarises the design, laboratory testing and construction to enhance the lakes performance during very strong seismic accelerations (Peak Ground Accelerations of up to 1.08g) expected during a maximum design earthquake originating from the Wellington Fault.
Keywords: Water Reservoir, Seismic Design, Geomembrane, Rock Buttressing, Seismic Risk Assessment, Wellington Fault
Kelly Maslin, Mark Foster, Len McDonald
A key requirement of assessing the tolerability of dam safety risks is the assessment of individual risk. The ANCOLD Guidelines on Risk Assessment provides guidance on acceptable levels of individual risk and some general guidance on the calculation of individual risk.
Individual risk is a key measure in the consideration of the tolerability of risk, ALARP and development of risk mitigation works. It is essential that there is consistency in the approach to estimating individual risk used across the dams industry.
This paper reviews the approaches taken to estimating individual risk across the dams industry both locally and internationally as well as the experience of other industries.
The paper includes a review of the various methods for estimating the vulnerability of individuals subjected to flood inundation based on historical fatality rates as well as identification of the individual most at risk
The paper then describes a method that has been developed based on the principles used for assessing individual risk due to other hazards, such as landslides. The method includes consideration of a range of factors such as warning time, temporal variation and vulnerability of the individuals most at risk. The method developed provides a transparent, defensible and pragmatic approach to estimating individual risk. Practical guidance and examples are also provided on the application of the method.
Keywords: individual, risk, exposure, fatality
The Bureau of Meteorology (the Bureau) is revising the current Intensity-Frequency-Duration (IFD) design rainfall estimates which are an essential component in the design of infrastructure. The current IFDs were developed by over 20 years ago using data from the Bureau’s network of rain gauges and adopting techniques for the statistical analysis of the data that were considered appropriate at the time.
The IFD Revision Project, which will provide revised IFD estimates in November 2012, uses a greatly expanded rainfall database in addition to adopting more statistically rigorous methods that are most appropriate to Australian rainfall data. The revised IFD estimates will be provided for durations from 1 minute to 7 days and Annual Exceedance Probabilities (AEPs) from 50% to 1%. The revised IFD information will be blended with the CRCFORGE estimates developed by each state to enable a smooth rainfall frequency curve to be derived from 50% AEP to 0.05% AEP.
Keywords: Design rainfall, Intensity-Frequency-Duration, IFD .