2019 Sydney Symposium
Innovations in Geotechnical Construction and Design
Harry Poulos and David Puller
The Australian Geomechanics Society (AGS) Sydney Chapter is holding its 23rd annual symposium on Friday 15 November 2019, on ‘Innovations in Geotechnical Construction and Design’.
Call for Abstracts
The symposium will showcase state-of- the-art practices, new research findings and case histories that demonstrate innovations in geotechnical design and construction. The organising committee invites papers on geotechnical aspects of transport infrastructure construction, site characterisation, numerical simulation, collapsed structures, reliability analysis and new insights into experiences, technologies and strategies.
The symposium presents an opportunity for professional engineers, researchers, specialist contractors, regulators, educators and students to meet and share their knowledge and experiences in geotechnical engineering.
Some Inadequacies of Common Design Procedures for Deep Foundations – Harry Poulos
This paper examines some aspects of common deep foundation design that the author considers may be inadequate. The following aspects are considered:
- Ignoring foundation interactions;
- Ignoring the beneficial effect of the raft;
- Assuming a rigid cap or raft;
- Over-simplification of the geotechnical profile;
- Ignoring the beneficial effects of basement walls;
- Ignoring the effects of ground movements;
- Ignoring kinematic effects in seismic design.
Each inadequate aspect will be considered in turn, with examples given of the possible consequences. Some lead to conservative designs, while others tend to be unconservative. Suggestions will be offered for addressing the perceived inadequacies, some of which are likely to involve the application of innovative techniques.
The Design and Construction of Very Deep Excavations – Recent Advances – David Puller
Technical advancements in construction plant, materials and numerical analysis tools have made possible a step change in the achievable depth of excavations required for infrastructure, building and mining projects. This has been in response to an increased complexity in such projects particularly in connection with rail, water and power infrastructure sectors around the globe. Such advances do not come without some risks and a clear understanding of the limitations of the techniques, capabilities of construction monitoring and the benefits of practical design details are key to successful execution. In addition, a sound knowledge of the behaviour and testing of materials particularly fresh concrete and support fluids is essential in the minimisation of defects in deep earth retaining structures, which can be extremely costly to remediate.
The following paper considers the state of the art in the construction of very deep and complicated excavations by making reference to a number of recent case histories, where records have been broken and new technologies have been deployed. The construction of diaphragm walls to depths well in excess of 100 m and with wall thickness of 1800 mm and using concrete with a 28-day cube strength in excess of 60 MPa are now possible, provided great care is taken. Improved verticality tolerances of better than 1 in 400, coupled with precise monitoring and advanced design techniques, means that the structural capacity of earth retaining walls in shaft construction have increased significantly which has led to the realisation of deeper excavations, together with deep openings which may be necessary for associated tunnels.
The author will also include the presentation of recent improvements in safety both in cage lifting, handling and splicing as well as around open diaphragm wall excavations. A better understanding of the causation of defects in concrete which has been placed under support fluid via a tremie, has been gained through painful experience and has greatly benefitted from the recent publication of useful guidance in Australia, UK and by the EFFC (European Federation of Foundation Contractors). This has led to a number of new site tests on fresh concrete for mix stability and bleed potential which are gaining increasing traction in the industry. In addition, the introduction of more stringent testing on support fluid such as bentonite during excavation means that instances of defects including leaks, inclusions and areas of poor concrete cover can be reduced. However, despite the availability of extensive guidance on good reinforcement cage detailing for diaphragm cages, examples of poor practice still remain, with great potential to lead to extensive defects such as mattressing which may compromise the durability of permanent works. The author will highlight examples of good and bad practice.
Geotechnical innovations in the tunneling industry
Application of Digital Technologies for Improved Geotechnical Design
Tentative topics (subjected to final paper submission)
- Ground improvement of Granville harbour wind farm foundations using CMC
- Geotechnical challenges for construction of diaphragm walls and foundation of Sydney’s tallest building, Crown Sydney Hotel Resort
- Design and construction of plastic geocellular rain water harvesting/stormwater detention tanks
- An empirical model to correlate rock mass classification and hydraulic conductivity of Hawkesbury sandstone in Sydney
- Listening to the earth: an unconventional scientific approach to understanding sub-surface ground conditions
- Innovative retaining wall design at Delvin’s Creek, ETTT project, Sydney
- In-situ waste characterisation for primary settlement assessment for high embankment of infrastructure projects built over municipal solid waste
- Applied borehole imagery for civil ground models
- Green square – enabling urban renewal through trenchless construction and smart retaining wall design
- Optimising precast cantilever walls founded in Sydney sandstone
- Ground improvement and verification for stage 1 IMEX earthworks
- A novel multiple-liner design for preventing desiccation of geosynthetic clay liners: an experimental investigation
- Seismic Slope Stability of a Tailings Storage Facility with Liquefiable Tailings
- Assessment of strength and performance of deep soil mixing columns and its implication for design – lessons learnt
- The approach of preload and surcharge release for embankments constructed over PVD improved soft soils
- Ali Parsa, JK Geotechnics (Organising Committee Coordinator)
- Sam Mirlatifi, John Holland (AGS-Sydney Chapter Chair/National Representative)
- Hadi Khabbaz, University of Technology Sydney
Hulskamp, JK Geotechnics
- Cholachat Rujikiat-
kamjorn, University of Wollongong
- AHM Kamruzzaman (Zaman), RMS
- Tony Gourlay, Mott MacDonald
- Miren Barinaga, Bachy Soletanche
About the speakers
Poulos graduated from the University of Sydney, where he took a bachelor’s degree, BSc in 1961 and his doctorate, PhD in 1965. His PhD research was supervised by Professor Edward H. Davis and was titled “The analysis of settlement of foundations on clay soils under three-dimensional conditions”. During 1964-65, he was an engineer at MacDonald Wagner and Priddle. From 1965 he was Lecturer, Senior Lecturer in 1969, Reader in 1972 and from 1982, Professor at the University of Sydney, where he is now Professor Emeritus. In 1976 he was awarded a higher doctorate degree DSc from the University of Sydney.
He has been involved worldwide in various basic construction projects, such as pile foundations for skyscrapers in Dubai (Burj Al Arab, Emirates Towers, the Burj Dubai, the tallest skyscraper in the world, where he performed the geotechnical testing), the Docklands Project in Melbourne, or 700 km Egnatia Odos motorway straight through Greece (2001 to 2005), where in particular the earthquakes played a role. Other projects included consultations with various offshore structures such as oil rigs.
David Puller has over 30 years experience in geotechnical contracting and consultancy working on major projects in the UK, Germany, Hong Kong, Spain, South Korea and the United Arab Emirates. As diaphragm wall expert he has designed some of the deepest diaphragm walls constructed and has managed the construction of major civil works. He has authored numerous technical papers, acted as one of principal authors on the 2nd and 3rd editions of the ICE Specification for Piling and Embedded Retaining Walls and has also co-authored the established text book Deep Excavations. As piling expert he has acted as Expert Witness in a major arbitration in Hong Kong.
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