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This paper outlines lessons learned from 8 years of regular operations and testing of 111 gates at 22 sites. It points out that the implementation challenges involved are not only technological in nature, but also encompass human factor and organizational issues. This is perhaps understandable since the initiative is part of the cultural shift to sustain gate reliability long-term.
An increase in gate testing frequency has led to the identification of more performance anomalies, ranging from deficiencies to operational failures. This finding may not be unique to a single dam owner. It leads to the following question to the general dam owner community: Are we testing our gates enough?
Melbourne Water (MW) has historically seen dam safety management as a civil discipline and has focussed on understanding and managing the civil assets at its dam sites. The recent addition of a mechanical engineering resource to the team responsible for the dam safety management has refocused attention on the mechanical and electrical (M&E) assets and provided a more holistic asset management approach to MWs large dams.
This paper discusses the process MW has developed over the past two years to improve their understanding and management of M&E assets. It centres on key process points for how MW has prioritised the development of M&E asset management programs on the basis of an autogenous ‘asset criticality’ rating system and has utilised ANCOLD comprehensive inspections to plan and implement new inspections and tests on dam M&E assets. The two case studies of Sugarloaf and Upper Yarra Reservoirs’ outlet works demonstrate the the benefits of the process to gain operational and technical knowledge of M&E assets, strategic importance to the water supply network, identifying risks therein and reallocate significant funding to address these risks as prioritised by asset criticality.Learn more
Nicole Anderson, M. Tooley, N. Vitharana, D. Moore
There is a significant stock of aging concrete dams in Australia which do not meet the requirements of modern dam safety practices. Where no site-specific information exists, current practice requires unduly simplified, conservative assumptions to be made. In some cases, this results in theoretical dam failure for load conditions which the dam has already experienced and safely withstood.Learn more
This paper outlines a range of site-specific field and laboratory investigations undertaken to reduce uncertainties in the assessment of two concrete gravity dams. For one dam, a suite of lab tests was undertaken to determine the residual reactivity so that potential future Alkaline-Aggregate Reaction induced expansion can be incorporated into any upgrade design.
The main purpose of the investigations was to reduce inherent uncertainties surrounding the design assumptions for strength and uplift pressures. This in turn reduced uncertainties relating to the risk profile of the dams.
The findings of this investigation will be of interest to dam designers and owners faced with upgrading concrete dams where a single traditional assumption can result in the difference between no upgrade or an upgrade worth several million dollars.
Keywords: Concrete gravity dams, testing, upgrade, Alkali Aggregate Reaction, dam design guidelines.
M. Tooley, N. Anderson, N. Vitharana, G. McNally, C. Johnson and D. Moore
There is a significant stock of aging concrete dams in Australia which would not meet the requirements of the current recognised dam safety practices applicable to concrete gravity dams.Learn more
In this paper, field and laboratory investigations undertaken for two concrete gravity dams are presented, these being Middle River Dam and Warren Dam both owned and operated by the South Australian Water Corporation. The field investigations included a comprehensive drilling program recovering core samples ranging in diameter from 61mm (HQ) to 95mm (4C), continuous imaging (RAAX) of the drilled holes and installation of piezometers. Geological logging of the holes and mapping of the unlined spillway were also undertaken. The laboratory program included the testing of concrete lift joints and concrete samples in direct tension, shear and compression.
Concrete in Middle River Dam is suffering from extensive Alkali Aggregate Reaction (AAR), and consequently a suite of laboratory testing is being undertaken to determine the current level of deterioration and residual reactivity so that potential future AAR-induced expansion can be incorporated into any upgrade design solution.
The main purpose of the study is to determine whether site-specific parameters can be used to re-assess the stability of these two dams as calculations, based on the current standards, have shown that the dams have exceeded the allowable factors of safety values at the storage water levels experienced to date.
The findings may be useful to dam designers and owners faced with the upgrading of concrete dams, where traditional assumptions can result in no upgrade or an upgrade costing several million dollars.