Buddhima Indraratna, Mark Locke and Gamini Adikari
The main objectives of the filter are to prevent erosion of the dam core, permit controlled passage of seepage flow through the dam and facilitate dissipation of excess pore pressures in the core. In most designs of dam filters, empirical methods based on particle size ratios have been used. These empirical rules are developed through extensive laboratory tests. Although the empirical rules benefit from directly or indirectly incorporating most factors affecting filtration, they cannot be extrapolated for distinctly different soils and do not describe the time dependent changes that occur within the filter medium.
Mathematical models can be formulated to explain the fundamental physics of particle interaction and migration, within a framework of well defined geohydraulic constraints. Considering the mass flow and momentum conservation principles; time dependent changes in particle size distributions, mass flow rates, retention capacity and base soil erosion rates can be simulated.
This paper reviews various empirical and mathematical models, based on the authors experience. A novel approach to large scale filtration is highlighted based on testing actual soil and filter materials from an Australian dam, in a new 500mm diameter apparatus.
Now showing 1-12 of 33 2963:
ANCOLD Environmental Guidelines have been under preparation for a considerable time. A brief for their preparation followed a resolution by the ANCOLD executive in 1991] that:
“ANCOLD should be seen by the profession and the community as a credible and informed source of information on the risks and benefits associated with dam projects.”
Why the guidelines were initiated, why they have taken the time they have to prepare and what they cover are described in this paper.
To the author’s knowledge, they are the only guidelines of their type, addressing the environmental effects of dams and associated works. It is hoped that they generate substantive debate. This paper initiates the public comments phase.
The paper has two purposes:
° = To introduce the guidelines ° To use the guidelines to introduce this environmental issues session of this conference
Peter Allen, Don Cock, Garry Grant and John Ruffini
The paper examines the performance of the Brisbane River and Pine River real time flood management system for the operation of Somerset Dam, Wivenhoe Dam and North Pine Dam during the 1999 flood event.
The February flood event, which was about 80% of the magnitude of the disastrous 1974 flood event upstream of Wivenhoe Dam, was the first major flood event to be managed by the system and it performed very creditably. The overall flood management system comprises:-
A network of 125 ALERT type rainfall and river height stations throughout the catchment; A data management system to facilitate data collection and data validation;
The paper describes the system and gives details of the performance of the system during the February event. It details the performance of the dams during the event and how this was optimised to maximise the safety of the dams and minimise impacts on those downstream.
Javad Tabatabaei! and Christopher Zoppou
Cotter Dam was constructed in 1912 to 19m and was raised to 31m in 1949. Due to its close proximity to a popular recreational resort, it is considered as a high hazard dam. It forms a storage with a capacity of only 4500ML and receives flows from a catchment area of 482km?. Concern about the ageing and structural integrity of Cotter Dam was expressed as early as 1967. There has also been a major revision of the Probable Maximum Flood (PMF) and new earthquake requirements for the dam. All these factors have contributed to the decision to undertake remedial works on the dam. The remedial work could be interrupted by flows over the spillway. This would increase the cost of the works because the construction equipment must be removed and reinstated (de/remobilisation) when there are flows over the spillway. Additional costs are also incurred for each day the construction equipment remains idle (standby). The total tender price therefore includes the cost associated with the remedial work as well as any standby and de/remobolisations. Risk analysis was used to establish the frequency the reservoir water level exceeds the spillway level. The risk analysis was used to select the successful remedial works tender.
Dr Judy Henderson
Against a background of several decades of increasingly polarised and acrimonious debate, the World Commission on Dams (WCD) was established in 1998 with a two year mandate to review the development effectiveness of dams, assess alternatives for water resources and energy development and develop internationally acceptable criteria and guidelines for future decision- making. This report discusses the role of large dams in development and the challenges of water resource management in the future. T the work program of the WCD is outlined and progress to date on fulfilling its mandate.
Andrew Day, Rod Bridges and Corrado Fabbri
A joint venture between Astaldi SpA of Italy and Thiess Contractors Pty Ltd of Australia (ATJO) has just completed a 95m high roller compacted concrete (RCC) dam on the island of Sulawesi in Indonesia. The dam which includes 528,000m’ of RCC was completed in September 1999 and will provide hydro-electric power for a nearby nickel smelting operation.
One of the largest RCC dams built in the region in recent times, the construction presented a number of unique challenges in particular placing techniques to cope with the heavy rainfall in the area as well the logistics to this remote location. Other aspects which are addressed in the paper include production rates, RCC placing systems (Rotec), dam formwork systems, aggregate sources, RCC mixes and waterproofing (membrane).
After early problems with the river diversion, the works were accelerated and completed to a very tight program. To enable dam construction to commence prior to river diversion the wall was advanced as a series of separate monoliths which led to a number of RCC placing innovations.