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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Now showing 1-12 of 17 2971:
Mike Marley, Greg Dryden, Geoff Eades, Edwin Brown, and Gary Huftile
Traveston Crossing Dam is proposed for construction at AMTD 207.6 km on the Mary River, about 25 km upstream of Gympie in South East Queensland. The Mary Valley at the dam site is located in a zone of complex geology resulting from formation in a tectonic accretionary wedge setting. This has been responsible for its complex geological structure, which has required a range of geological and geotechnical investigation and interpretation techniques to develop a model on which to base the dam’s preliminary design. This paper describes the tectonic history and the innovative techniques used in developing the geological model for the dam foundation.
The investigation involved aerial photograph interpretation, geological mapping; geotechnical drilling, including water pressure testing; seismic refraction profiling; downhole geophysical logging; excavation and geological mapping of large excavations; and hydrogeological investigation involving investigative drilling and pumping tests.
A Vulcan 3-D computerised geological model was constructed using borehole data, seismic refraction interpretation and downhole geophysics interpretation. The geological model has been used in the development of the preliminary design and confirms that the foundations are suitable for the proposed structure.
Keywords: Dam Foundation; Geophysics; Investigation Tectonics; Geological Strength Index Kinetic Analysis
The Resource Management Act 1991 provides regional councils with responsibility for the control of taking, use, damming and diversion of water for the purpose of promoting sustainable resource management. The Act enables councils to develop plans, including objectives, policies and rules, to assist it carry out its functions. Otago Regional Council has an operative plan, Regional Plan: Water for Otago, which contains various provisions relevant to controlling damming and storage of water.
In Otago, where irrigation is significant, most surface water is over-allocated. Water for irrigation is largely allocated through deemed resource consents (issued by the Wardens Court under the Mining Acts of 1898 and 1926) which now have an imposed expiry date of 1 October 2021 under the Resource Management Act. Deemed consents have priority access allocations and are largely excluded from the provisions of the regional plan. Water resources are not efficiently utilised under the current regime, with water from dry areas transported long distances to areas with abundant water, and surface water taken when ground water is a more appropriate resource.
Otago Regional Council is undertaking a plan change program to allow smooth transition from deemed consents that ensures water resources are efficiently allocated and water is used efficiently after 2021. The paper describes the results of consultation undertaken with irrigators and discusses the role of irrigation infrastructure raised at those meetings.
Efficient water resource management requires Council to develop a policy regime that promotes water resource and use efficiency as a priority and encourages community based water management for efficient on farm use. Also, irrigators need to develop new storage and distribution infrastructure managed and operated at an inter farm – community level.
Changes to the Building Act, giving regional councils responsibility for dam safety and building controls for dams, create opportunities for greater integration of dam construction and management with water resource management under the Resource Management Act. This paper explores an opportunity for major redesign of water infrastructure development and management for the future prosperity of Otago.
Keywords: Building Act, Resource Management Act, water, storage and distribution infrastructure, resource efficiency
Stuart 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
Steven 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
Marius Jonker, Francisco Lopez and John Bosler
This paper describes the safety evaluation and development of remediation options for Clover Dam, a 28 m high slab and buttress structure situated in the alpine region in northeast Victoria, Australia. The review was particularly challenging considering the complexity, age and cracked condition of the dam structure, which required the development of an analysis method for this type of dam.
Completed in 1953, Clover Dam is one of five dams in the Kiewa hydroelectric scheme. The 76 m long dam comprises a 45.7 m long covered slab and buttress section, supported on each abutment by concrete gravity sections. The review was undertaken as a result of severe cracking occurring since the early 1970s and because a detailed design review had not been undertaken since its construction.
Current guidelines for the safety review of existing dams provide little detailed information on slab and buttress dams. Consequently, a methodology was developed to analyse Clover Dam. This methodology could also be applied in the review of this type of dam in general, and is currently being used for safety assessments of three other slab and buttress dams.
This paper focuses mainly on the dam structural assessments undertaken during the safety review. The structural analyses involved 3-D finite element analyses for thermal, static and earthquake loading.
The outcome of the review was that both the gravity and buttress portions of the dam do not meet current design standards. The development of practicable remediation options was complicated by the operational constraints and the restricted access to those areas within the dam where remedial works were required.
Keywords: Slab and buttress dam, 3D finite element analysis, seismic assessment.