2007 – Current international state of practice for the seismic design and analysis of appurtenant structures at dams
Steve O’Brien
Appurtenant structures associated with a dam play and important part to the dam’s operation. For these structures it may be important that their functional and structural integrity is retained in the event of a notable earthquake, particularly when they are required to release water from the reservoir in a controlled manner to lower the storage following an earthquake. Research has been conducted into the current state of practice for the seismic design and analysis of these structures, including review of the main issues for seismic effects, documentation of case histories and review of current research, international guidelines and standards. The general assessment philosophy was found to be relatively consistent internationally, however, the adopted assessment procedures were found to vary. The status of the current ANCOLD earthquake guidelines has been provided in relation to the current international state of practice for various types of appurtenant structures.
Keywords: Appurtenant structures, performance criteria, seismic performance, seismic analysis.
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2007 Papers
2007 – Design inputs for stability assessment of dams on New Zealand greywackes
Learn moreStuart Read and Laurie Richards
Many dams in New Zealand are founded on greywacke, a typically hard, closely-jointed rock mass. This paper describes the characteristics of greywacke rocks based on field mapping, laboratory testing and rock mass classification, and gives examples of design inputs for dams, in particular concrete structures. Unweathered, intact rock materials have unconfined compressive strengths generally above 100 MPa and moderate to high modulus ratios. The rock masses, which comprise sandstones and mudstones, are commonly tectonically disturbed and have an unusual combination of very high intact strength and joints with low persistence. The effect of these properties on rock mass deformability and strength is illustrated by estimation of dam foundation deformability from tiltmeter measurements and assessment of critical foundation failure mechanisms from estimates of defect and global rock mass strengths.
Keywords: foundations, dam design, rock mass strength, rock mass deformability, greywacke
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2007 Papers
2007 – Wave seiching and run-up effects in Lake Aviemore due to seismotectonic displacement of the lakebed
Learn moreM.G. Webby, C.J. Roberts and J. Walker
The Waitangi Fault passes under Aviemore Dam and Lake Aviemore in the Waitaki Valley in the South Island of New Zealand. Several studies were undertaken in the period 1999-2004 to understand the geology and faulting in the Waitaki Valley and, in particular, to determine the potential for future movement on the Waitangi Fault (Walker et al. 2004). As part of the Aviemore Dam Seismic Safety Evaluation (ADSSE) Project, a numerical hydrodynamic study was undertaken to analyse the pattern of seiche waves generated by fault displacement and to determine the potential wave run-up on the dam face to overtop the dam.
Ground displacement along the Waitangi Fault gives rise to initial wave trains on the lake surface travelling in opposite orthogonal directions away from the fault line and approximately parallel to the axis of Aviemore Dam. These initial wave trains are refracted by the lakebed as they approach the eastern and western lake shorelines and are then reflected off these shorelines. The reflected wave trains interact to create a very disturbed lake surface before a long-period seiching response is set up due to repeated lakeshore reflection. The seiching response is a bimodal one, with a cross-lake component and an along-lake component. The along-lake seiche waves run up on the relatively steep embankment part of the dam and on the vertical face of the concrete gravity part.
Keywords: Seismotectonic, fault, displacement, lake, dam, numerical, hydrodynamic, model, seiche, wave, solitary wave, wave run-up, dam overtopping.
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2007 Papers
2007 – Improving safety and hydraulic efficiency of dams with physical model studies
Learn moreSteven L. Barfuss and Blake P. Tullis
An important aspect of improving the safety of dams is selecting designs that are both hydraulically efficient and cost-effective. A powerful tool that can be used as part of the hydraulic structure design process is a physical model study. To obtain maximum benefit from the model, it should be implemented as a part of the design process rather than as a post-design verification phase. A model study included early in the conceptual design phase can also provide increased flexibility to the designers.
Hydraulic model studies can often provide cost-effective answers to difficult problems. Some of the issues that can be efficiently resolved using model studies include optimizing spillway head-discharge relationships to increase reservoir storage while minimizing upstream flooding potential, controlling downstream scour, quantifying hydraulic uplift forces and/or overturning moments of dam structures, evaluating alternatives for structure retrofit or repair, and optimizing control gate sequencing during floods. Model studies also allow the engineer to simulate prototype performance (e.g., three-dimensional flow patterns, velocities, pressures, scour potential) over the full range of expected discharges. Quick and easy changes to the model can be made at minimal cost when evaluating the performance, safety and economic impact of various design alternatives.This hands-on model study approach to dam safety represents a tool that in some cases is underutilized.
Brief discussions of several physical model studies conducted at the Utah Water Research Laboratory, Utah State University in Logan, Utah, USA, are presented to illustrate key points of the paper. The primary objective of each of these model studies was to provide and/or improve the safety of the dam and the spillway while minimizing construction costs. This paper discusses the cost-effectiveness and hydraulic improvements that can be achieved through physical model studies.
Keywords: Physical models studies, design, hydraulic efficiency, dam safety, construction costs
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2007 Papers
2007 – Planning to secure South East Queensland’s future water infrastructure
Learn moreRussell Paton and David Murray
The South-East Queensland Regional Water Supply Strategy is securing future water supplies, which includes a regional water grid and new water storages. The Queensland Government’s contribution to future water supplies includes Traveston Crossing Dam on the Mary River, Wyaralong Dam on the Teviot Brook, and Bromelton Offstream Storage and Cedar Grove Weir on the Logan River.
Queensland Water Infrastructure (QWI) was established by the Queensland Government in June 2006 to progress feasibility studies, design and construction of this new water infrastructure. QWI commissioned SunWater to investigate much of this infrastructure to preliminary design level for the impact assessment process and as supporting information for potential alliance partners for the delivery of the projects. The work undertaken included extensive geotechnical investigations, hydraulic modelling, hydrologic modelling and design activities. This paper outlines the investigations associated with the preliminary design of this infrastructure and process of risk and opportunity identification to establish the program and budgets for these projects.
Stage 1 of Traveston Crossing Dam is to be constructed by the end of 2011, with a storage capacity of 153,000 ML providing a yield of 70,000 ML each year. The design adopted for the dam consists of a roller compacted concrete structure across the valley floor with an earth embankment section on the left abutment. In order to limit inundation upstream and mitigate flooding in Gympie, a gated spillway on the right abutment has been adopted. The Traveston Crossing Dam has an estimated project cost of $1,700 million.
The design developed for the Wyaralong damsite provides a reservoir with storage capacity of 103,000 ML and a yield of 21,000 ML each year when operated in conjunction with Cedar Grove Weir. Preliminary designs have been prepared for three types of dam, which are all considered technically feasible for the site. They are a roller compacted concrete dam, an earth and rockfill dam and a concrete faced rockfill dam. The Wyaralong Dam has an estimated project cost of $500 million.
The Bromelton Offstream Storage, of earthfill construction, provides a storage capacity of 8,000 ML and Cedar Grove Weir, a sheet pile structure, provides a storage capacity of 1,000 ML and both are to be constructed by the end of 2007.
Keywords: Planning, Traveston Crossing Dam, Wyaralong Dam, Bromelton Offstream Storage, Cedar Grove Weir, Queensland, risk.
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2007 Papers
2007 – Comparison of New Zealand and North American dam anchoring practices
Learn moreStephen McInerney, Donald A. Bruce and John Black
An historical database of North American dam anchoring experience has been recently assembled in the United States. This database clearly shows the historical development of dam anchoring technology, particularly with regard to corrosion protection practices over four decades. The results of this research are significant to dam owners worldwide because of the number of examples in the database.
The paper describes New Zealand experience with dam anchoring against the background of the historical practices in North America and the main conclusions drawn from the United States research.
Keywords: Post-tensioning, anchor, corrosion protection, historic database, dam remediation
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