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.
— OR —
Now showing 1-12 of 31 2966:
G.W. Ashman, C.M. Hamilton and N.J. Hall
Consideration of the need to accommodate environmental flows in the operation of major dams is a relatively new requirement in South Australia. Recognition of environmental water requirements has been promoted through the COAG water industry reforms and the State Water Resources Act. The South Australian Water Corporation is working with other Government agencies on environmental flow projects that will potentially involve three of the Corporation’s large dams. This presentation will summarise the work done to date on establishing environmental flow releases from these storages. The presentation will give the SA Water perspective on the regulatory, environmental, social and operational aspects of the environmental flow issue.
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.
J. Matthews, A. Crichton, G. Gibson
Glenmaggie Dam is a 37m high concrete gravity dam, which was constructed from 1919 to 1927. A
design review, which was carried out in line with ANCOLD Guidelines, (SMEC 1999) indicated that the dam did not meet the ANCOLD Guidelines for earthquake. This was despite the fact that the dam was stabilised in 1989 by the addition of 70 post-tensioned ground anchors. Faced with the possibility of having to perform a major upgrade to the dam, Southern Rural Water opted to undertake a more detailed assessment of the seismic loads and to carry out further analysis of the dam using the time history method. The time history method uses an accelerogram to model the forces acting on the structure throughout the earthquake and takes into account the continually changing direction of these forces. It can also be used to determine the size of any permanent
displacements caused by the earthquake, which can then be compared to the maximum allowable permanent deformation of the dam to determine if they are acceptable. The study was carried out by GHD Pty Ltd and also utilised updated seismic information for the dam site provided by the Seismology Research Centre and a geological assessment of the local faults by the URS Corporation. This paper discusses the methods used to determine the seismic loads; the techniques used in the study and the outcomes and follows the process from a dam owner’s perspective.
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.
Bob Wark, Colin Bradbury, Michael Somerford and Michelle Rhodes
The Harvey Dam project is a major component of the Water Corporation’s Stirling-Harvey Redevelopment Scheme, which was developed to provide potable water to Perth. The scheme will deliver 34 GL/annum or about 10% of Perth’s supply. The project timetable was tight. The decision to proceed with the scheme, made in June 1998, required Harvey Dam to be ready to impound water by June 2002.
Construction of the Harvey Dam was complicated by the following:
These and other issues required the development of risk management strategies for the project. The construction risks were allocated within the contract to provide for an equitable sharing of risk between the Contractor and the Principal. The paper describes the development and implementation of the risk management strategies and what lessons have been learnt from the process.