Bill Hakin, Phillip Solomon, Peter Siers Bruce Goddard
Lyell Dam is located on the Coxs River near Lithgow NSW Australia. It was constructed in 1982 to supply cooling water to Delta Electricity’s Mt. Piper and Wallerawang power stations.
In 1994 the storage capacity of the dam was increased by 7,500 Ml by raising the embankment height and installing two 3.5m high inflatable rubber dams on an enlarged and slightly raised spillway sill. Two significant failures of the rubber dams in 1997 and 1999, led the dam owner to seek an alternative method of maintaining the increased Full Supply Level (FSL) whilst still providing spillway capacity for the design flood. Although the lost storage has a certain strategic value to Delta Electricity, the main reason for restoring the capacity to its former level was to preserve the environmental and recreational use of the reservoir for the local community.
Following a detailed review of options, Delta Electricity chose to regain the former FSL with the Hydroplus Fusegate System. Because of the freeboard available at Lyell dam it was possible to design the Fusegates such that none tip before the 20 000 AEP flood.
In order to derive accurate as-built levels and dimensions of the existing spillway, new laser scanning methods were utilised to create a digital 3-D model of its complex shape.
The water retaining concrete Fusegates were poured in-situ and designed without anti-crack reinforcement. This innovation was only possible by use of a special design mix and careful temperature control/monitoring during concrete placing.
This is the first installation of the Hydroplus Fusegate System in Australia. The paper examines the philosophy of approach and various unique methods used in the application of the System during the design and construction stages.
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Now showing 1-12 of 31 2966:
Brian Walford and Ross Killick
Increasing salinity in Australian river systems is a major issue that is attracting attention from politicians, environmentalists and the wider community. The successful coexistence of mining and agriculture in the Hunter Valley has resulted in the need to tackle river salinity with a cooperative approach to not only contain salinity, but also reduce it. Mining companies have participated in the development of a tradeable emission scheme to manage the discharge of surplus saline water, resulting in the construction of mine water dams that are designed to release a large volume of saline water in 2– 3 days.
N. Vitharana, G. Bell, J. Jensen and J. Sinha
When the storage was enlarged in 1971, Wyangala Dam provided a storage of 1220Gl. The original concrete gravity dam was completed in 1936 with an initial storage of 37.5Gl. The enlargement comprised the construction of a central core earth and rockfill dam utilising the existing concrete gravity as an upstream “toe” dam. At its deepest section, the toe (concrete gravity) dam is 60m high with a base length of 40m. The rockfill dam is 85m and the full supply level is at 75m. Two cylindrical reinforced concrete intake towers were constructed utilising the crest of the toe dam as their bases.
Screening level analyses commissioned by The NSW Department of Land and Water Conservation have recommended that detailed seismic assessment of the toe dam and intake towers be undertaken. In 2001, GHD Pty Ltd undertook inelastic time-history analysis using site-specific seismic loadings. Toe dam was modelled together with the rockfill dam using a 2-dimensional model. Intake towers were modelled incorporating the composite behaviour of concrete and reinforcing steel with limited concrete strains to prevent the loss of cover concrete and the buckling of longitudinal steel. Time-history analyses supplements by conventional pseudo-dynamic analysis procedures.
This paper described the constitutive modelling, structural analysis criteria, evaluation of hydrodynamic and dynamic earth pressures and the findings.
C.F. Wan, R. Fell, M.A. Foster
This paper presents the findings of experimental investigation of the rate of piping erosion of soils conducted at the University of New South Wales.
Two tests, namely the Slot Erosion Test and the Hole Erosion Test, have been developed to study the erosion characteristics of a soil. The erosion characteristics are described by the Erosion Rate Index, which indicates the rate of erosion due to fluid traction, and the Critical Shear Stress, which represents the minimum shear stress when erosion starts. Results of the two laboratory erosion tests are strongly correlated. Values of the Erosion Rate Index span from 0 to 6, indicating that two soils can differ in their rates of erosion by up to 106 times. Coarse-grained soils, in general, are less erosion-resistant than fine-grained soils. The Erosion Rate Indices of coarse-grained cohesionless soils show good correlation with the fines and clay contents, and the degree of saturation of the soils, whereas the Erosion Rate Indices of fine-grained cohesive soils show moderately good correlation with the degree of saturation. The absence of smectites and vermiculites, and apparently the presence of cementing materials, such as iron oxides, improves the erosion resistance of a fine-grained soil.
The Hole Erosion Test is proposed as a simple index test for quantifying the rate of piping erosion in a soil, and for finding the approximate Critical Shear Stress corresponding to initiation of piping erosion. Knowledge of these erosion characteristics of the core soil of an embankment dam aids assessment of the likelihood of dam failure due to piping erosion in a risk assessment process.
R.M. Dawson, A. Orange
Karapiro dam is the last in a line of hydro-electric dams on the Waikato River, in New Zealand’s North Island. Investigations identified a potential deficiency in parts of the dam under seismic loading. Detailed investigations and analysis narrowed the deficiency to a low strength clay seam under the concrete gravity left abutment structure. An innovative approach was taken to solving the stability problems at minimum cost, without lowering the storage lake, which would have had significant environmental and social impacts. The process of design and construction was overviewed by an international board of review.
Construction was completed in three main stages with further investigation and design refinement between. The main contract was completed over about eight months and included detailed concrete mix and pour schedule design to control stress development due to temperature gradients for the 2000 + cubic metres of mass concrete placed. While the extent of work was relatively small, the quality control, programming, and presence of a full reservoir throughout demanded a high degree of communication and co-operation between the Principal, Designer and Constructor. Despite some surprises during construction, the project was completed within budget and formed strong bonds between all those involved. This paper briefly describes the design process, and focuses on construction, from the point of view of the Owner, Constructor and the Designer.
Tony McCormick, John Grimston, Robin Dawson
Project Aqua is a proposed hydroelectric and irrigation resource sharing development on the Lower Waitaki River in New Zealand’s South Island. The NZ $1 billion project aims to deliver approximately 540 MW peak power at an economically viable price, while minimising environmental and social impacts. Application of traditional hydro concepts in historical studies for the same reach has not provided an economic solution. The current proposal challenges conventional thinking in many areas with innovative concepts allowing a significantly lower cost while not sacrificing safety or flexibility.
Development of storage may involve high social and environmental impacts. No significant storage is needed for Project Aqua as the operation of existing upstream dams can be modified to provide for peaking demand and maintenance of minimum flows. The river intake offers innovative features with its very low profile structure. The concept allows a departure from the traditional barrage or dam diversion and maintains an open braid for jet boat and fish passage. This concept has proven to be a major feature in the overall project progression to the current stage.
The largest impact component of the scheme is the eight canals designed to carry 340 cumecs over 63 km through six power stations. Cuts and fills form the canals with locally derived materials used for the embankments and lining. Expensive lining has been minimised by balancing flow exchange with groundwater through the cut and fill sections.
Feasibility design has been completed and resource consents are currently being sought. This paper will cover the significant design features and impacts.