David Scriven, Lawrence Fahey
Paradise Dam is located approximately 20 km north-west of Biggenden and 80 km south-west of Bundaberg on the Burnett River in Queensland. The dam was designed and constructed under an alliance agreement with construction completed in mid 2005. It is a concrete gravity structure up to 52 m high, the primary construction material being roller compacted concrete (RCC).
In January 2013 the flood of record was experienced at the dam with a depth of overflow on the primary spillway reaching 8.65 m following heavy rainfall in the catchment from ex-tropical cyclone Oswald. The peak outflow was approximately 17,000 m3/s. This equated to a 1 in 170 AEP flood event. When the flood receded it was discovered that the dam and surrounds had suffered severe damage in a number of locations including: extensive rock scour downstream of the primary dissipator and the left abutment, damage to portions of the primary dissipator apron, and the loss of most of the primary dissipator end sill.
SunWater initiated a staged remediation program to manage the dam safety risks and by November 2013 had completed the initial Phase 1 Emergency and Phase 2 Interim repairs. Phase 3 of the program was to implement a comprehensive Dam Safety Review (DSR) and a Comprehensive Risk Assessment (CRA). The DSR became arguably the largest ever undertaken by SunWater and included: extensive geotechnical investigations, large scale physical modelling, numerical scour analysis, stability analysis, and an extensive design assessment. This paper describes some of the key aspects of the DSR undertaken related to the flood damage.
K.A. Crawford-Flett, J.J.M. Haskell
Dam inventories can provide a comprehensive understanding of a region’s dam population; from dam quantity, type, age, height, and purpose; to ownership profiling and broad-based regional risk assessment using GIS applications. Historically, New Zealand has lacked a comprehensive inventory of dam assets, instead relying on local and industry knowledge to characterise the dam infrastructure and its key properties, issues, and risks.
This paper presents a cross-sectional characterisation of dams in New Zealand, based on the recent compilation and analysis of a New Zealand Inventory of Dams (NZID). The NZID is the first inventory of its kind for NZ dams, comprising almost 1200 unique structures over 3 m in height. Inventory data was sourced from existing publications, NZSOLD, and regional authorities. The analysis of anonymised inventory data provides an understanding of the number and distribution of assets, along with characteristic physical properties (construction material, height, age, purpose).
Statistical comparisons are drawn in relation to published international dam inventories. Similarities and differences in the international dam populations are noted, particularly with regard to construction era and type. The NZ portfolio is unique in that dams are typically shorter in height, and a significant proportion of structures serve the hydroelectric and energy sectors.
Analysis of the new NZID confirms the need for research that is focused on the long-term performance of aging earth dams, particularly those exceeding 40 years of age. In addition to informing research needs and foci, the new NZID provides statistics on the dam population with far-reaching industry and management applications
The SRC operated seismic network is one of the largest privately owned and operated seismic networks in the world. Importantly it bridges the situation awareness gap between the information often provided by national seismic networks, of earthquake magnitude and location, and the emergency response managers questions of “What effects will this event have on my assets?” together with “What should we now be doing to mitigate the event?”
Software development of the Quick Quake app and improved automation of PDF report generation means that detailed, bespoke client specific earthquake response reports that incorporate asset earthquake resistance and failure consequence aspects can be produced by duty seismologists within reduced timeframes.
Preliminary earthquake locations computed by the SRC operated network for the two ML 4.7 Korumburra events in March 2009 and the ML 5.6 Moe earthquake of June 2012 were significantly closer to the final computed locations than those published by any other authority. The network additionally provides bonus outcomes of highly accurate detailed seismic activity maps that reduce uncertainties for Probabilistic Seismic Hazard Assessments (PSHAs) and attenuation data that will be used to develop regional specific ground motion models.
Sean Ladiges, Robert Wark, Richard Rodd
The use of permanent, load-monitorable post-tensioned, anchors for dam projects has been in place for approximately 35 years in Australia. Since then, over 30 large Australian dams have been strengthened using this technology, including the world record for anchor length (142 m – Canning Dam, WA) and size (91×15.7 mm strands – Wellington Dam, WA and Catugunya Dam, TAS).
In order to achieve the design life of 100 years expected of these anchors, an ongoing program of monitoring, testing and maintenance is required, to identify and rectify the initiation of corrosion or loss of pre-stress. Guidance for maintenance and testing regime for post-tensioned anchors in dams is provided in the ANCOLD Guidelines on Dam Safety Management (2003). The various conditions which may affect the performance of the anchor with time, such as anchor type, ground condition and loading fluctuations are not covered in the Guideline.
This paper reviews the implementation and results of anchor monitoring programs by Australian dam owners. The first part of this paper provides a summary of the testing and monitoring programs currently being implemented. The second part of the paper reviews the aggregated anchor load test results from a number of Australian dam owners, and identifies trends in anchor response over time following installation.
The paper aims to assess whether the recommended anchor testing regime proposed in ANCOLD (2003) is appropriate and cost effective, using evidence from recent load test data which has become available following the writing of the guideline. The lessons learnt from anchor maintenance programs will also be discussed.
The National Seismic Hazard Assessment 2018 (NSHA 18) project intends to revise the existing seismic hazard map (AS1170.4 2007) for Australia. Geoscience Australia (GA) are leading the project along with a consortium of seismologists, geologists and earthquake engineers.
The NSHA 18, due to be released in 2018 is of great importance to dam owners and operators. The project intends to incorporate a comprehensive approach to seismic hazard, particularly in modelling uncertainty and variability.
The Global Earthquake Model (GEM) is an international consortium of scientists, engineers and policy makers. One of the primary aims of GEM is to provide a uniform set of tools for analysis in seismic hazard and risk. GEM was established to provide a framework for global standards in comparing risk analysis, awareness and actions in an effort to increase resilience to vulnerable communities.
The NSHA 18 will use the GEM framework in order to meet its own objectives for the new upcoming hazard map. The Seismology Research Centre will contribute to the NSHA 18 in three areas. Firstly, to produce a unified earthquake catalogue where GA will homogenise magnitudes to a uniform scale. Secondly, to produce a number of applicable alternate seismotectonic models, and thirdly, through the contribution of ground motion data collected over the last forty years within Australia.
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.