2013 – Proposed Kotuku flood detention dam
Joseph Camuso, Bruce Howse, Vaughan Martin and Don Tate
The proposed Kotuku Flood Detention Dam has been designed to reduce flooding within Whangarei City. This paper describes the potential benefits and the impact of the project on the community and the environment. It also covers the engineering challenges encountered during the design phase of the project. In particular, the dam site is located within a complex geological area, including a basalt lava flow on the left abutment, and site constraints required a twin emergency spillway design. If the risks associated with the dam are managed effectively, the proposed dam will provide a valuable asset to the community.
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Papers 2013
2013 – Case study of risk assessment for dam safety management decision-making in Korea
Learn moreJeong Yeul, Lim
For various historical reasons and some technical reasons, the safety of dams has been evaluated using an engineering standards-based approach, which was developed over many years. It was used initially for the design of new dams, but increasingly has been applied over the past few decades to assess the safety of existing dams. Some countries have carried out risk assessments of existing dams that included both the structural and hydraulic safety of the dam and social risk. These methods developed by other countries could be adapted to assist in decision-making for dam safety management. Unfortunately, methods for risk assessment of dams were not established in Korea. This study outlines a beginning risk analysis for structural safety management. The first stage consisted of research on the present domestic dam safety guidelines and reviewing operations for management systems of dam safety abroad. Also, dam risk analysis requires reliable data on dam failure, past construction history and management records of existing dams. A suitable risk analysis method of dams for structural safety management in Korea is use of event tree, fault tree and conditioning indexes methods. A pilot risk assessment was carried out for two dams. The dam risk assessment process was thus established, and we learned the importance of risk assessment. The future includes additional research and risk analysis to develop the system.
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Papers 2013
2013 – Design considerations in the continuous concrete buttressing of existing concrete gravity dams
Learn moreNicole Anderson and Nihal Vitharana
A large number of aging concrete dams in Australia may not meet the requirements of modern dam safety practices. In addition, there is an ever-increasing demand for the supply of water. Continuous concrete buttressing is a method of strengthening existing dams which allows the dam to be raised to augment the storage capacity at an incremental cost.
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This paper explores the key design considerations involved in concrete-buttressing existing concrete gravity dams. Critical aspects considered include storage level during construction, interface drainage, interface shear transfer, the relative strength of existing and new concrete and the behaviour during the heating and cooling phases of the heat-of-hydration. The discussions will be of relevance to asset owners and water authorities faced with upgrading existing dams in a time where there is an increasing demand for security of supply of water resources. -
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Papers 2013
2013 – Fault rupture hazard assessments for dam foundations: examples from contrasting tectonic environments
Learn moreTim McMorran and Alan Hull
Accurate assessment of potential fault rupture hazard in dam sites is a critical factor in managing dam safety. Assessment of the location and activity of a surface fault within or near an existing or proposed dam can be technically challenging, expensive and affect design and construction schedules.
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Three examples from regions of relatively high, moderate and low tectonic activity are used to illustrate that fault rupture hazard assessment is generally feasible in regions with high rates of tectonic activity, historic earthquake occurrence and the presence of Quaternary and Holocene-age landforms and sediments. In regions with relatively low rates of tectonic activity and landscape development, the fault rupture hazard assessment is more challenging.
The examples illustrate that robust geologic and geomorphic analysis provides critical information on the fault rupture hazard at existing and proposed dams. These analyses assist dam owners to obtain a more complete understanding of the fault rupture hazard at their facility, and support their longer term risk assessments. -
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Papers 2013
2013 – Risk-based management of two water bodies at a Queensland coal mine
Learn moreRob Campbell, Christopher Dann and Mark Foster
Queensland contains some of Australia’s most significant reserves of mineable metallurgical coal, which is an essential raw material used in the production of steel. The area also has large deposits of thermal coal, used for electricity generation.
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For the many active open cut and underground coal mines in Queensland, the enduring operational focus is to maximise returns and productivity, while still meeting key safety and environmental responsibilities.
Maintaining open cut pits in a dewatered state is often a key factor in achieving optimal productivity of an open cut mine. In Queensland, for many mines it is not always practical to maintain all pits in a dewatered state, given the subtropical climate and significant rainfall that can occur during the wet season, between the months of November and March. In effectively managing mine water while maintaining production, it is not unusual for excess mine water to be temporarily stored in a designated open cut pit.
The typical scale and arrangement of open cut pits at mine sites in Queensland is such that relatively deep and high volume pits can be separated by relatively narrow “landbridges”, consisting of in-situ material or mine spoil. The situation can therefore arise where a significant volume and head of mine water is stored in one pit, with mining operations continuing in an adjacent pit, and the landbridge is required to perform as a water retaining structure. This is a scenario that might not have been considered when the landbridge was originally constructed. This paper presents a study of two such landbridges at either end of a mine pit in Queensland, over a 5 year period from 2008 to 2013, with mining activities in the pit ranging from dragline pre-stripping to open cut mining, to large scale construction works and underground mining. By employing a long term interactive approach with mine operations personnel and utilising quantitative risk management techniques, risks were effectively managed, helping the mine to maintain operations while meeting safety and environmental requirements. -
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Papers 2013
2013 – Cotter Dam construction challenges and innovations
Learn moreB. Perrin and J. Vida
The Cotter Dam project represents the most significant infrastructure project in the Australian Capital Territory (ACT) since Parliament House in 1988. Enlarging the Cotter Dam has increased the Cotter reservoir capacity from 3 GL to 78 GL, representing a 35% increase of ACTEW Corporation’s total reservoir capacity for the ACT region and providing water security to facilitate future population growth.
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At 87 m high, Cotter Dam is the tallest Roller Compacted Concrete (RCC) dam in Australia. Construction began in October 2009, with excavation of the dam foundation commencing in March 2010. With typically 05H:1V slopes up to 115 m high, excavation posed a number of challenges. RCC placement commenced in August 2011 and continued until December 2012.
Innovation and continuous improvement were crucial to the success of the project. From development of specialised mechanical tools for the abutment excavation, to use of precast, to mechanical paving of the downstream RCC steps, construction practice on Cotter Dam established a number of new benchmarks for RCC dam construction.
This paper will describe the construction innovations used to overcome the challenges associated with construction during foundation preparation and RCC placement for the Cotter Dam Project.