2016 – Characteristics of Near Fault Ground Motions for Seismic Design
Paul Somerville
This paper describes the unique characteristics of near-fault ground motions for use in developing ground motions for the design and evaluation of dams that are located close to identified active faults. These characteristics include near-fault rupture directivity effects, permanent ground displacements, and hanging wall effects. In Australia, active faults make a significant contribution to the Maximum Credible Earthquake (MCE) only at near-fault sites when Probabilistic Seismic Hazard Analysis (PSHA) is used. However, some sites may be close enough to nearby or even more distant identified active faults that a Deterministic Seismic Hazard Analysis (DSHA) produces MCE ground motions that are for larger than those obtained using a probabilistic approach even for very long return periods. Knowledge of the unique characteristics of near-fault ground motions should be applied to the development of ground motions for the design and evaluation of dams that are located close to identified active faults.
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Papers 2016
2016 – Why may Coastal Reservoir Dominate Future Water Supply?
Learn moreAssoc. Prof. Shu-Qing Yang
Next to air, freshwater has been always considered as a key resource, central for economic development and human’s basic needs. Currently the total population is about 7 billion, and by 2050, global population is projected to be 9 billion. An additional 10 more Nile Rivers are needed, and the water demand is increasing steadily and significantly. The dams industry has successfully solved the water deficit problems in many places for most of the time, but more and more countries and regions are gradually resorting to other emerging technologies like desalination, wastewater recycling and rainwater tanks etc. as they believe that a dam is the 20th century technology and has too many significant negative impacts. However, available data show that the global water consumption is only 5~6% of annual runoff, e.g., Australia’s water use is about 20km3, but the runoff lost to the sea is up to 440km3. A coastal reservoir is a freshwater reservoir inside seawater, aimed at the development of freshwater from the sea without desalination. The 1st generation of coastal reservoir has emerged in China, Singapore, Hong Kong and Korea successfully, but generally its water quality is not as good as that in inland dams. The 2nd generation of coastal reservoirs has been developed and its water quality is at least comparable with the water in existing reservoirs like Warragamba dam. The application of coastal reservoirs in Australia is discussed and the feasibility is investigated. The preliminary designs of coastal reservoirs in SE Queensland, Sydney, Melbourne, Adelaide and Perth show that the coastal reservoir is a feasible and effective technology for Australia’s water crisis.
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Papers 2016
2016 – Kangaroo Creek Dam Embankment Raising and Stabilisation – Balancing Competing Objectives
Learn morePeter Buchanan, Malcolm Barker, Paul Maisano, Marius Jonker
Kangaroo Creek Dam located on the Torrens River, approximately 22 km north east of Adelaide, is currently undergoing a major upgrade to address a number of deficiencies, including increasing flood capacity and reducing its vulnerability to major seismic loading.
Originally constructed in the 1960s and raised in 1983, recent reviews have indicated that the dam does not meet modern standards for an extreme consequence category dam.
The original dam was generally constructed from the rock won from the spillway excavation. This rock was quite variable in quality and strength and contained significant portions of low strength schist, which broke down when compacted by the rollers. The nature of this material in places is very fine with characteristics more akin to soil than rock. Review of this material suggests that large seepage flows (say following a major seismic event and rupture of the upstream face slab) could lead to extensive migration of the finer material and possible failure of the embankment. However, it is also envisaged that the zones of coarser material could behave as a rockfill and therefore transmit large seepage flows, which may result in unravelling of the downstream face leading to instability.
This paper addresses the design of the embankment raising and stabilising providing suitable protection against both these possible failure scenarios, which tend to lead to competing solutions. The final solution required the embankment to be considered both as a CFRD and a zoned earth and rockfill embankment.
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Papers 2016
2016 – Life Loss Estimation from Flood Events: A New Approach to Population Redistribution with Uncertainty
Learn moreWoodrow 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.
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Papers 2016
2016 – Comparing CRCFORGE Estimates and the New Rare Design Rainfalls
Learn moreJ.H.Green, C.Beesley, C.The, S.Podgerand, A.Frost
The ability to estimate design rainfalls for probabilities rarer than 100 years or 1% Annual Exceedance Probability (AEP) is an essential part of dam hydrology. The earliest means of estimating rare events consisted of a pragmatic curve fitting procedure between the 50 and 100 year design rainfalls and the Probable Maximum Precipitation. In the 1990s a more rigorous method of estimating design rainfalls as rare as 2000 years was developed – the Cooperative Research Centre – FOcussed Rainfall Growth Estimation (CRC-FORGE) method. CRC-FORGE estimates were derived for Victoria in 1997 followed progressively by each of the other states. Over the subsequent two decades CRC-FORGE estimates were an integral part of the risk assessment of large dams – being used to determine the AEP of the Dam Crest Flood.
The Bureau of Meteorology will soon release new rare design rainfall estimates for probabilities to 2000 years. The new rare design rainfalls are a significant improvement on the CRC-FORGE estimates as they have been derived using up to date data; contemporary analytical techniques and a method that is consistent across Australia.
However, there are differences between the CRC-FORGE estimates and the new rare design rainfalls. These differences do not constitute a systematic change to the CRC-FORGE estimates but rather vary with location; duration and probability. The results of a detailed comparison between the CRC-FORGE estimates and the new rare design rainfalls are presented together will an assessment of the possible impacts on previous estimates of the AEP of the Dam Crest Flood.
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Papers 2016
2016 – Constructions of a High Capacity Post Tensioned Permanent Carbon Fibre Ground Anchor
Learn moreDr Matthew Sentry, Nabeel Elias
Although permanent ground anchor technology has advanced in leaps and bounds over the past two decades, the focus of anchor technology has been on developing techniques to minimise the risk of component and system failure due to corrosion. The advancements in structural materials available in the market in recent years have enabled research into alternative materials for permanent ground anchor systems.
Carbon fibre has become a significant structural alternative throughout North America for bridge and building construction as well as repair and structural strengthening of deteriorated/corroded structures. These advancements and the necessity to investigate alternative materials for anchor systems have led to research in understanding the long term performance effects of using carbon fibre products as an alternative to steel tendons in permanent ground anchors.
Following on from the advanced research works at Monash University and Geotechnical Engineering which investigated the durability performance of various available CFRP strands when used as an alternative to conventional steel tendons in permanent ground anchor systems, Geotech developed the first post tensioned ground anchor system using CFRP strand.Following laboratory based trials and small scale bun barrel tests, Geotech was able to successfully design, construct, install and stress the first 27 strand post tensioned CFRP ground anchor installed into Yass Dam. The CFRP strand was stressed and locked off at 4,000kN. Real time monitoring has been installed to monitor the load throughout the anchors service life.
This paper provides the details of the construction, installation and stressing of the first CFRP anchor installed into a dam structure.
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