Australian Geomechanics Society South Australia & Northern Territory – 1997 Meetings
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February, 1997
The Re-Use of Sediment Drained from the Patawalonga
Lyn Sanders and Tony Read
Between the middle of 1995 and the middle of 1996, approximately 300 000 m3 of sediment was dredged from the Patawalonga Basin. The sediment was deposited in ponds along Tapleys Hill Road and the water drained from it. In July 1996 accelerated drainage measures were instituted which allowed the material to be removed from the ponds early and used in the construction of a golf course immediately south of the ponds. The area had previously been used for waste disposal and some of the sediment was used to form an additional cap over the landfill.
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March, 1997
Tailings Management at Olympic Dam - Current Practises and Future Options
Jeremy Folwell
Tailings management at Olympic Dam involves the monitoring and control of solid and liquid components of the tailings slurry. Tailings slurry is deposited in thin layers using a spigot system from the perimeter of each cell. The solids settle onto the tailings beach whilst the supernatant liquor is collected from the centre of each cell. The liquor is decanted into evaporation ponds. Additional solids storage capacity is provided by upstream raising of the perimeter embankments. This involves construction of embankments partly over the previous embankment and partly over dried tailings. A portion of the coarse fraction of the tailings is separated using hydrocyclones for use underground in cemented aggregate fill (CAF). A new tailings disposal system is being considered for use at Olympic Dam. The system, called Central Thickened Discharge (CTD), involves the deposition from a number of central risers to form a series of intersecting cones. Field trials will be carried out to confirm design parameters and further evaluate the viability of the system for use at Olympic Dam.
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April, 1997
Blanchetown Bridge Replacement - Geotechnical Investigation
Richard Herraman, Matthew Duthy
Site work has started for the construction of a new bridge at Blanchetown. This bridge will be one of the biggest built in the state in recent times. A seismic study to provide information for the alignment of the new bridge was performed by Coffey Partners International. The geotechnical investigation for the new bridge was done by the Department of Transport and Rust PPK. In theory, getting information for the design of footings and earthworks is relatively straightforward, as is the design of such items. In practice things are more interesting. The speakers will address such topics as:
- the public and private sectors working together on geotechnical investigations
- how to design and construct an efficient and effective pile group
- how to predict embankment settlement
- what to do about embankment settlement (as well as Mr Terzaghi)
- interaction between the new bridge and the existing bridge.
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May, 1997
Annual Half-Day Seminar - Environmental Geomechanics
Roger Parker, Linton Johnston, Clive Jenkins, Michael Cannell, Alex Eadie, Alan Ockenden, James Begg, Dr Peter Mitchell
- Geoenvironmental practice in Australia
- Urban stormwater contaminants
- Heavy metals in the sediments of constructed wetlands: safely locked up or mobile and toxic?
- Instrumentation for environmental geomechanics
- Environmental auditing of contaminated land in SA
- Managing urban catchments
- Environmental and geotechnical aspects of the Halifax St Depot site
- Geotechnical aspects of the Ratchaburi industrial waste landfill project Thailand
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June, 1997
Melbourne Crown Casino - Geotechnical Issues
Max Ervin
The Melbourne Crown Casino, billed as one of the largest in the world, has been built on about a 6 hectare site on the south bank of the Yarra River in Melbourne. The $1.6 billion project includes 11 hectares of underground car parking, on two levels, theatres, gaming halls, restaurants and a 40 storey hotel. The Casino opened on May 8, 1997. Golder Associates undertook geotechnical investigations for the project, on behalf of the Casino developer, Crown Limited. Ground conditions at the site comprise up to 20 metres of soft to firm clay (Coode Island Silt) overlying stiff clay, dense sands and gravels with the Silurian age basement rock of variably weathered siltstone encountered at about 30 metres depth. Basalt rock is present at shallow depth over the northern part of the site. The two level basement was undrained and the associated buoyancy forces accommodated as necessary by tension piles socketed into the siltstone or the basalt. A groundwater protection system was developed comprising a bentonite-cement cut-off wall to about 10 metres depth, with additional protection from the installation of an hydraulic wall comprised of wick drains installed at close centres to about 20 metres depth. Max Ervin was extensively involved with the investigation, design and construction phases of this very challenging project. He will describe the geotechnical investigations undertaken, the design solutions adopted, and the numerous construction issues which arose. In particular, the groundwater protection system developed to avoid regional effects, the construction of some 950 bored piles with bentonite slurry support, and stability issues associated with the temporary cut batters used for the basement excavation will be discussed.
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July, 1997
Art Gallery of SA - Deep Basement Construction
Carlo Muneretto
The presentation will cover the construction of the recently completed $26 million extensions to the Art Gallery of South Australia. Particular emphasis will be on the construction of the 10 m deep basement as redesigned to accommodate "top down" construction and the locally developed interlocking bored pile retaining wall technique. The key features to be addressed are:
- The unconventional "top down" method of construction of the basement floors. With this method of construction, the floors provide lateral support for the perimeter wall during excavation. On this site the method eliminated the need for earth anchors which would have compromised the structural integrity of the surrounding heritage buildings
- The design and successful performance of the innovative "interlocking bored pile perimeter retaining wall system", developed locally by Rust PPK, and which was used in lieu of the originally proposed secant pile wall.
- The "system approach" used by Baulderstone Hornibrook, which resulted in the successful implementation of these two design solutions with such ease.
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August, 1997
The Holdfast Shores Development at Glenelg - Geotechnical Aspects - Onshore and Offshore
Bob Boorman, Doug Smart, Dr Peter Mitchell
The development, currently under construction, includes large breakwaters to create a safe harbour for the Kangaroo Island fast ferry and new marina berths; about 150 apartments and penthouses; new hotel and tourist accommodation; a marina pier with restaurants, shops and taverns; a key; and a mixed recreational area. Completion of the project is scheduled for 2001. The predicted cost, including an associated development at West Beach, is $140 million. The presentation will include a description of the project, with particular emphasis on its geotechnical aspects both onshore and offshore. The coastal engineering aspects of the project will also be discussed, including the numerical and physical modelling done for the design of the proposed breakwaters, and an outline of the proposed sand management systems to be installed to mitigate the interruption of the natural longshore sand drift by the breakwaters.
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September, 1997
Adelaide AirportRunway Extension
Richard Cavagnaro, Roger Grounds
This project involved the diversion of Tapley's Hill Rd and the extension of the main runway of Adelaide airport to allow fully loaded 747 jets to take off and land. Discussed were: the site investigation techniques used and the test results obtained with particular emphasis on the very soft soils encountered in the bed of the Patawalonga creek, the pre-load testing conducted in the grounds of the airport; and the excavation and filling techniques employed.
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October, 1997
Landslide Risk Assessment
Alan Moon
Landslide hazard and risk assessments have been carried out by private practitioners and public bodies for many years. Recently there have been attempts to set up a more formal framework of risk assessment and management. Alan will explain the principles of landslide risk assessment and some of the common terms. He will illustrate the principles with case histories involving railway cuttings and large landslides on reservoir slopes. Alan Moon is an engineering geologist with Golder Associates. He has carried out landslide risk assessments in Australia and overseas for many years. Alan is a member of several national and international committees on landslide risk assessment and hillside construction including the taskforce recently established by the Institution of Engineers and the Australian Geomechanics Society in response to the Thredbo tragedy. Alan's presentation should be of interest to a broad range of people in the land and infrastructure development industries including engineering consultants, local and state government bodies, contractors, planners and developers.
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November, 1997
Life on a Commune
Richard Herraman
Between the middle of 1995 and the middle of 1996, approximately 300 000 m3 of sediment was dredged from the Patawalonga Basin. The sediment was deposited in ponds along Tapleys Hill Road and the water drained from it. In July 1996 accelerated drainage measures were instituted which allowed the material to be removed from the ponds early and used in the construction of a golf course immediately south of the ponds. The area had previously been used for waste disposal and some of the sediment was used to form an additional cap over the landfill.