There is a significant body of knowledge in relation to assessing the impacts of earthquakes on earth and rock fill dams which has led to a number of widely recognised and accepted methodologies for the calculation of potential deformations from an earthquake event. However, limited research has been conducted into the assessment of blasting impacts on earth structures. This has led to an adoption of earthquake analysis methods in the assessment of blasting impacts on earth structures without adequate consideration to the difference between the stresses and displacements imposed on an embankment as a result of a blast as opposed to an earthquake. Adopting earthquake analysis techniques may result in conservative vibration limits being imposed when undertaking blasting near embankment dams which may have negative financial impacts.
This paper explores the risks associated with blasting adjacent to earth fill dams and details the difference between stresses and displacements imposed on an embankment by a blast versus an earthquake.
This paper also discusses previously adopted approaches to assessing potential impacts associated with blasting and the limitations associated with adopting a pseudo-static and simplified permanent deformation analysis for blasts modelled as equivalent earthquakes. Finally, the paper proposes an alternate risk based analysis approach.
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Assoc. 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.
David Piccolo, Gareth Swarbrick, Garry Mostyn, Bruce Hutchison, Rodd Brinkmann
Hillgrove Resources owns and operates Kanmantoo copper mine some 44 km southeast of Adelaide.
An important feature of the mine is its tailings storage facility (TSF) which is fully lined with HDPE, and double lined at the base, fully under drained, has a secondary underdrainage system for leak detection and a multi-staged centralised decant system. This onerous design of the TSF was developed in consultation with DMITRE between 2007 and 2010 amid concerns of groundwater protection and effective water management.
The Authors were approached in 2010, following construction of the initial stage of the TSF, and charged with developing the design to increase storage from 13 to 20 million tonnes, as well as optimising the design and construction of future stages.
This paper presents the more interesting aspects of the design and construction optimisation between 2010 and 2016 including:
The design and construction approaches have been scrutinised and accepted by regulatory authorities, and implemented by the mine operator over a period of 6 years. The paper includes lessons learnt during the implementation process.
Paradise Dam is located on the Burnett River 20 km northwest of the town of Biggenden in Queensland. It is a gravity dam with a height of 37 metres and a total capacity of 300,000 ML. It was primarily constructed to service local agriculture.
The dam features a complex outlet works contained within a tightly constrained footprint. It provides for irrigation releases, fish passage and power generation. Additionally, the outlet is required to pass very high environmental flows of up to 270 m3/s.
The dam was subjected to major flooding in 2013 resulting in significant damage to the mechanical equipment associated with the outlet works, and severe scour downstream of the spillway.
Since construction, the operating range for the environmental outlet has been restricted. A rough operating zone has been identified through which the gates are quickly moved through. It is believed to be caused by the dynamics of the gates and the upstream conduit arrangement. Failure of the downstream stainless steel liner associated with the conduit has also occurred. The environmental outlet lacks the ability to be isolated from the storage, complicating the maintenance / modification of the gates. At the time of design, it was agreed by the alliance partners that major maintenance of the gate would be planned for when the reservoir was low, being below the intake bellmouth.
The irrigation release valves suffer from high vibration levels during operation. Component failure and severe corrosion have also been experienced.
This paper details:
Operational and maintenance experiences and restrictions since commencing operation including the impact of flooding;
Investigation and testing of environmental gate dynamics and the impact of these on the intake tower;
Failure of the environmental conduit liner, investigation and proposed rectification;
Proposed method to enable servicing of environmental gates without the use of a bulkhead and without draining the storage;
Proposed enhancements to irrigation valves to reduce vibration and extend service life.
BJ Rochecouste Collet, PC Blersch, AL Olivier
The paper shows how multidisciplinary engineering can create future-proofed solutions for dam management and how innovation is bringing those advancements to life. It includes the retrofitting of a small hydropower station to an existing dam structure, enhancing the use of the dam. The paper also reveals design, technical and project finance considerations underpinning the multi-disciplinary services.
Water supply in South Africa’s economic hub of Gauteng journeys from the Lesotho Highlands Water Project (LHWP) through three river systems that converge in to the Vaal Dam from which the water is treated and pumped for domestic usage. One of those systems delivers water originating in Lesotho to discharge into the Ash River. The Ash River was, by origin, a small river with an environmental reserve flow of 50 l/s. However, with the LHWP significantly adding flow, the annual average increased to 24,500 l/s (24.5 m3/s) and is set to increase further with future phases of the scheme. To mitigate significant erosion caused by the greatly increased flow, several structures were erected along the river, including the Botterkloof Dam. Whilst the energy was dissipated in the dam’s spillway, a private developer studied if the water could be used for energy generation. The river also offered some rapids some 1.6 km downstream, which also showed potential for hydropower generation. An option to combine the two sites was also considered.
Aurecon conducted the feasibility study in 2010 for both sites, including the combined option, which concluded that there would be significant benefits in the implementation the projects in two separate schemes. This boasted many advantages including reduced capital investment, reduced social impact (canoeist), reduced geotechnical risks, and lesser land acquisition leading to a better return on investment. Aurecon are currently providing engineering, procurement and construction management (EPCM) services for the entire project. Construction of the 4.4 MW hydropower station commenced construction in September 2014 and was commissioned ahead of time and under budget.
The founding conditions under the proposed hydropower station location, comprising interbedded sandstone and mudstone was fairly poor with the mudstone effectively decomposing in less than two days. The Botterkloof dam was build on a thick layer of sandstone which dips quite steeply towards the right bank. The right bank on the other hand comprises an old paleo channel. The Boston A dam, located on the left bank immediately adjacent to the Botterkloof Dam, is founded on the weather mudstone and the spillway is grass lined. The power station construction was constructed in the narrow space in between the two existing dams – the Botterkloof Dam (owned by the Department of Water and Sanitation (DWS), Government of South Africa) and the adjacent privately-owned Boston A Dam. Permission had to be obtained from the respective owners and all regulatory permits approved before the project could be submitted to the South African Renewable Energy Independent Power Producer Programme (REIPPP) implemented by the Department of Energy (DoE) of the South African Government.
Another significant challenge in the construction itself included the need for deep excavations through the left embankment of the Botterkloof Dam and adjacent to the spillway stilling basin whilst such construction needed to be done without affecting operations and stability of either of the two dams.
The solution was a shallow intake, followed by a cut and cover concrete penstock leading to a compact hydropower station housing a single 4.4 MW vertical “Compact Axial Turbine” Kaplan turbine ending in the tailrace, which was rotated at 90 degrees.
Jason Needham, John Sorensen, Dennis Mileti, Simon Lang
The potential loss of life from floods, including those caused by dam failure, is sensitive to assumptions about warning and evacuation of the population at risk. Therefore, the U.S. Army Corps of Engineers engaged with social scientists to better understand the process of warning and mobilizing communities that experience severe flooding. This improved understanding enables dam owners to better assess the existing risk posed by their assets and investigate non-structural risk reduction measures alongside structural upgrades.
In this paper, the U.S. Army Corps of Engineers research is summarised to provide general guidance on the warning and mobilization of populations at risk for practitioners assessing the potential loss of life from dam failure. This includes commentary and quantification of three primary timeframes: warning issuance delay, warning diffusion, and protective action initiation. A questionnaire for estimating these parameters is also introduced, alongside a case study application for an Australian dam.
This paper also summarises the current understanding of how to reduce delays in determining when to issue warnings, increase speed at which warnings spread through communities, and decrease the time people spend before taking the recommended protective action. These insights will help all people involved with emergency management, including those tasked with developing Dam Safety Emergency Plans.