Lake Buffalo located on the Buffalo River near Myrtleford in Victoria was constructed in the 1960s as a cofferdam for the then proposed Big Buffalo dam. Consequently, the dam was designed for a short life (<10 years) and design features and criteria for a permanent dam were not implemented.
Critical features include a primary spillway with three vertical lift gates, two outlet conduits located
through the spillway piers, a single upstream valve on each outlet conduit for regulation and isolation, and a multi-part bulkhead which is installed in front of the valves for inspection and maintenance.
With the continued operation of the dam beyond 60 years, upgrades appropriate to a permanent dam have been implemented, including addressing deficiencies with spillway gate hoists lifting equipment and redundancy of the outlet conduit vales. This proved challenging, as the operation of spillway structures does not readily align with industry or Australian Standards. This paper will outline the issues encountered, their resolution and the lessons learnt during this upgrade work.
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This paper provides an outline of the design and construction of the works undertaken to refurbish the 120 year old intake tower at Mundaring Weir. The project drivers included asset condition, hydraulic capacity, reduction in unusable storage, and reduction in evaporation from the reservoir. The one off sale of this water together with the present value of the reduction in evaporation pays for the project construction and is a significant response to climate change that is taking place in the region. The effects of Alkali Aggregate Reaction (AAR) compromised the efficacy of the Intake Tower operating as a dry-well, while the small diameter and significant corrosion of cast iron pipes and valves had severely diminished the service capacity of the structure. The solution implemented in this project included: lining the Intake Tower with a 37 m long by 2.7 m diameter 316 stainless steel liner; construction of a new inlet 15 m below the reservoir surface using a bespoke underwater coring rig; relining of existing pipes through the dam wall; and new outlet control pipework and valves downstream of the dam.
Multiple-arch dam technology enjoyed a certain popularity between the fifties and seventies, but was later discontinued for practical reasons. The multiple-arch dam that is the subject of this paper is especially peculiar since it was built using prefabricated elements and a combination of several pre-stressed steel systems.
This dam consists of 17 buttressed arches with a maximum height of 35 m on a limestone and dolostone foundation. It has a crest length of 531 m and a 15 hm3 reservoir. After 55 years in operation, several apparent degradations have surfaced and a study on the safety of the dam is currently being carried out.
The main concern is the dam’s structural safety, which is apparently linked to the integrity of the post-stressed steel elements and the precast elements in the arches. This paper describes the approach chosen for the remediation study, the visual inspection, and the tests developed on the post-stressed steel and concrete, in order to feed a 3D numerical model of the structure.
This paper will explore the differences in pore pressures resulting from saturated and unsaturated seepage (pore pressure) analysis. It will also evaluate some conventional recommendations, such as the inclusion of essential components of the embankment dam and omission of inessential components. In addition, the identification of inessential components will be discussed.
Finally, pore pressures obtained from these analyses will be compared to monitoring data in order to identify the most appropriate seepage (pore pressure) model.
In conclusion, advantages and disadvantages of each method will be discussed and recommendations will be provided in order to gain the most appropriate results.
The results of this paper can be used for designing new embankment dams or safety reviews of existing dams, particularly when there is lack of reliable monitoring data.
New technology and outputs from flood forecasting systems can raise issues for dam safety managers in how they use uncertain information to make critical dam safety decisions. In particular, making operational decisions around pre-releases based on forecast inflow presents challenges. In this case dam safety risk needs to be weighed up with other risks such as increasing downstream flooding, or being able to supply water into the future. The process of developing a flood forecasting system should be a close collaboration between the developers and the users. This ensures that outputs provide meaningful information that can be used to support operational decision-making in a flood or emergency response situation.
The volume-of-fluid (VOF) technique was employed to develop a Computational Fluid Dynamics (CFD) model for comparison to physical measurements available from the Eildon Dam model in Australia for validations purposes. The water surface in the downstream chute of the spillway was observed to be mostly comprised of fully developed aerated flow. The free surface is physically measured as located between the mixing and upper zones, thus investigator judgement is critical to achieve reliable measurements. The mixing zone is also characterized by surface waves to complicate matters even further. A challenge arose to develop a post processing methodology that replicates as closely as possible the measuring technique used by the physical modeller for direct comparison of results, using a novel method which utilises Poisson probability of exceedance applied to the free surface.