Australian Geomechanics Society Victoria – 2004 Meetings

• February 23, 2004

  2004 Poulos Lecture - Tunnels and Excavations: Ground Movements and the Construction Process

  Professor R Neil Taylor

  Infrastructure development invariably involves construction of excavations in the ground. These may be long and horizontal - tunnels - or short, often wide and vertical - basement excavations or cut-and-cover tunnels. The excavations need to be formed safely, so stability can be an issue, and increasingly there are major concerns about the assessment and control of deformations caused by their construction.

  The central theme of research within the Geotechnical Engineering Research Centre at City University is the investigation of ground movements associated with tunnels and deep excavations during the construction process and a major part of the work has been the application of geotechnical centrifuge modelling of these problems. An important feature of the research has been the use of digital image processing techniques that allows overall patterns of ground movements to be determined, enabling centrifuge modelling to progress from a tool for investigating stability mechanisms to one that can give valuable and detailed insight into pre-failure deformations.

  The lecture will present examples of research on tunnels and deep excavations focussing on the overall patterns of ground movements caused by these constructions, the interaction of ground movements with nearby structures and how various structural elements effectively control the magnitude and spread of ground movements.

• March 16, 2003

  Road Pavements

  Andrew Papacostas – An Overview of New Austroads Pavements Guide

  Andrew is the Manager of VicRoads Geopave’s Pavement Technology Services. He will provide a brief outline of the new Austroads Pavement Design Guide due for release later this year.

  Ross Paul – Lime Stabilisation of Earthworks Materials & VicRoads New Standard Specification – Sec 290

  Ross is the Principal Consulting Engineer – Ross Paul and Associates. He will provide a description and photographs of the process and a clause-by-clause explanation of the recently revised VicRoads Standard Specification Section 290 – Lime Stabilisation of Earthworks Materials.

• April 21, 2004

  2004 John Jaeger Memorial Award Lecture - The Mechanics of Discontinua: Engineering in Discontinuous Rock Masses

  Dr Ted Brown

  The John Jaeger Memorial Award is presented every 4 years at the ANZ Geomechanics Conference and the award is given by the AGS to an individual for contributions of the highest order over a lifetime commitment to the geotechnical profession in Australia. At this year’s ANZ Conference in Auckland the John Jaeger Memorial Award Lecture was presented by Ted Brown on the topic of ‘The Mechanics of Discontinua: Engineering in Discontinuous Rock Masses’.

  The lecture highlights a number of challenges that rock mechanics pose in engineering practise as rock engineering is rendered more challenging than most other branches of engineering by the complexity and variability of the basic material involved. In particular, rock masses are distinguished from other engineering materials by the presence of a range of inherent discontinuities. The lecture reviews the basic mechanics of discontinua and the historical development of the characterisation, testing, and analytical and numerical tools available to the engineer working with discontinuous rock.

  Ted Brown is a graduate of the Universities of Melbourne (BE 1960; MEngSc 1964), Queensland (PhD 1969) and London (DSc(Eng) 1985). He has held eminent positions at James Cook University, Imperial College of Science and Technology, London, and the University of Queensland. In 2001, Ted resumed his careers in engineering practice as a Senior Consultant with Golder Associates Pty Ltd. On Australia Day 2001, Ted was appointed a Companion in the Order of Australia, for “services to the engineering profession as a world expert in rock mechanics and to scholarship through promotion of the highest academic and professional standards.”

• May 11, 2004

  Rankine Lecture Downunder 2004 – Numerical Analysis: A Virtual Dream or Practical Reality?

  Professor David M Potts

  The development of numerical analysis and its application to geotechnical problems over the past 20 years have provided geotechnical engineers with an extremely powerful analysis tool. However, the use of such analysis is still not widespread, and when it is used there is all too often evidence of bad practice. Part of the reason for this is a lack of education and of guidance, especially from codes of practice, as to the appropriate use of such methods of analysis. Clearly, some form of initiative is required to promote good practice and allow the full potential of this analysis tool to be realised, both from a safety and an economy perspective. This lecture begins by reviewing the key advantages of numerical analysis over conventional analysis tools, and then debates whether or not it can replace the conventional analysis tools in the design process. Examples from engineering practice are used extensively to illustrate the arguments both for and against the use of numerical analysis.

  The power of numerical analysis to predict mechanisms of behaviour will be clearly demonstrated with the implication that conventional analysis tools could soon become extinct. Attention will then be focussed on some of the pitfalls that commonly arise and some of the problems related to the use of numerical software. These will be shown to be both significant and extremely worrying and must be resolved if numerical analysis is ever going to fulfil its enormous potential. The successful use of the analysis tool requires a user to be proficient in many areas, some of which are not covered adequately either at undergraduate or postgraduate level. To rectify these deficiencies, changes in the education of geotechnical engineers are necessary, with all the implications this brings to the profession. The lecture will conclude by discussing some of these issues.

• June 10, 2004

  EH Davis Memorial Lecture 2003 – Stability Analysis: New Solutions for an Old Challenge

  Professor Scott Sloan

  In practice, geotechnical stability analysis is usually performed by a variety of approximate methods that are based on the notion of limit equilibrium. Although they appeal to engineering intuition, these techniques have a number of major disadvantages, not the least of which is the need to presuppose an appropriate failure mechanism in advance. This feature can lead to grossly inaccurate predictions of the true failure load, especially for realistic problems involving layered materials, complex loading, or three-dimensional deformation.

  A much more rigorous method for assessing the stability of geostructures became available with the advent of the limit (or bound) theorems of classical plasticity in the 1950s. These theorems can be used to give upper and lower bounds on the predicted collapse load (a most valuable property in practice), do not require assumptions to be made about the mode of failure, and use only simple strength parameters that are familiar to geotechnical engineers. Although many ingenious bound results have been derived using both analytical and numerical methods, the true power of the limit theorems has been greatly restricted by the need to develop specific solution strategies for each practical problem. Over the last decade, the speaker and his group at the University of Newcastle have developed powerful new methods for performing stability analysis that combine the limit theorems with finite elements and optimisation. These methods are extremely general and can deal with layered soil profiles, anisotropic strength characteristics, complicated boundary conditions, and complex loading in both two and three dimensions. Indeed, they have already been used to obtain new stability solutions for a wide range of practical problems including soil anchors, slopes, foundations under combined loads, excavations, tunnels, mine workings, and sinkholes.

  This Lecture will give a brief outline of the new techniques and consider a number of practical applications. Future research developments will also be highlighted.

• July 21, 2004

  Joint Technical Meeting on Tunnelling (AUCTA) – Geotechnical Investigation for Tunnels: How Much is Enough?

  Les McQueen, Andrew Wapling

  Les McQueen is a Principal of Golder Associates, who specialises in investigation and design for underground structures. Les’s recent experience includes a number of hydro electric schemes in the Philippines; M5 East Motorway tunnels and Lane Cove in Sydney. He also acted as Financiers tunnel specialist for a consortium bidding the Mitcham Frankston Project.

  Les will discuss the approach to geotechnical investigation, objectives, philosophy and comment on investigation techniques and the data required for ground characterisation, rock mass classification and estimating rock mass parameters and thus potential failure mechanisms. What is needed for success and how much investigation? The level of investigation for several tunneling projects will be compared. His emphasis will be on hard rock tunnels.

  Andrew Wapling manages the Tunnels and Underground Structures Group of Connell Wagner in Victoria. Andrew’s recent experience includes major projects such as Singapore’s North East Line underground metro extension project, Sydney’s New Southern Railway Extension and Cross City Tunnel. He is currently working on the project delivery of a number of Melbourne Water’s proposed tunnels.

  Andrew will discuss the requirements of a tunnel designer through the various typical phases of a project development. He will address the parameters used in a design and the sensitivity of the design to variation in these values. This leads to a consideration of risk. Designers are often requested to advise clients on a suitable investigation programme, or the adequacy of available information. The response to this question must be phrased in terms of risk assessment and risk allocation and be given with an understanding of the contractual arrangements that will be used.

• August 18, 2004

  Cementitious Stabilisation of Unbound Road Pavements

  Dr Jayantha Kodikara

  Australia has the largest road length per capita, comprising over 800,000 km of roads. Australia also has the largest road freight of any OECD country measured per capita or per unit GNP. Because much of this network is aging and traffic volumes and loads are increasing, large sums of tax payers’ funds are annually spent on road rehabilitation. In-situ cementitious stabilisation is commonly used to rehabilitate unbound pavements, giving it a new lease of life. This is considered to be an environmentally friendly approach in comparison to new construction because it reuses the old materials. In addition, cementitious blends utilising industrial waste products such as slag and fly-ash could also be used in place of cement. Typically, 2 to 6% cementitious additives by weight are used to produce a stabilised pavement. Equipment have been developed that could carry out deep-lift-recycling of old pavements down to 400 mm or so.

  Despite the technological advancement, rational design methods of these pavements are still being developed. Currently, the design is primarily based on protecting against the flexural fatigue failure due to traffic loading. However, pavement distress could also occur due to shrinkage cracking and associated moisture related problems. At Monash University, we have researched on the behaviour of stabilised materials over the last four years or so. Particular attention was given to compressive and tensile strength development, shrinkage and cracking development, and capillary moisture ingress. More recently, we have started to work on salt ingress into pavement materials and associated pavement deterioration modelling.

  This seminar will present an overview of the results of this research, paying particular attention to a conceptual approach on how the environmental conditions, and associated shrinkage and moisture related distress could be addressed at the pavement mix design stage. The work to be reported may also be relevant to other stabilisation projects in traditional geotechnical engineering. Hand-outs of the presentation will be distributed during the seminar.

• September 15, 2004

  Engineering & Construction in Difficult Ground With Reference to Melbourne Docklands

  Peter McDonald, Mark Sheldon, Drew Bennett

  The concept of adding value through Geotechnical Engineering is particularly relevant to developments in difficult ground conditions. Tonight's speakers will examine the challenges in characterising complex and variable materials and how to manage identified risks to overcome these limitations.

  Workshop

  An opportunity to view and examine typical problematic soils in a laboratory environment and to discuss with colleagues the aspects of investigation, testing, and interpretation of data and the merits of various foundation solutions. A suite of soil samples from the Yarra Delta sequence will be on display, together with samples of stabilised Coode Island Silt.

• October 20, 2004

  Groundwater Management – Citylink, Deformation Properties of Limonite and Hydrogeology of Gippsland Basin

  Chris Boyd – Management of Groundwater System for Citylink Tunnels, Melbourne

  The management of the groundwater system in the vicinity of the Citylink Tunnels is concerned with protecting the Tunnels themselves as well as private and public assets above the tunnels. The groundwater management includes monitoring of over 100 standpipes and vibrating wire piezometers, monitoring of over 500 survey pin, and monitoring and control of the groundwater recharge system. The groundwater recharge system consists of permanent and passive recharge wells and a Water Treatment Plant, which allows water collected from the tunnel to be recharged back into the selected aquifers. The use of a database and GIS software tools allow rapid and easy review of groundwater and ground surface trends. Citylink’s initiative to construct a water treatment plant has solved a water disposal problem and reduced the reliance on mains water.

  Amanda Barrett – Field Assessment of the Strength and Deformation Properties of Limonite

  Detailed field investigations have recently been undertaken in the limonitic tropical soils of the South Pacific Region for a large industrial complex in New Caledonia. In situ investigations included piezo-Cone Penetrometer Tests (CPTU), Standard Penetration Tests (SPT), field and hand vane, pocket penetrometer tests, Menard pressuremeter testing and cross-hole seismic testing. Deformations of subsurface material under trial surcharge loading were measured using a magnetic extensometer. Several of the field techniques outlined were performed in close proximity allowing comparison of the interpreted soil properties through standard correlations. This presentation compares and discusses the variations in soil properties assessed from different field techniques and compares them to properties assumed from observations of the soil under surcharge loading from a trial embankment.

  Jurgen Schaeffer – Hydrogeology of the Gippsland Basin

  An overview of research into the Hydrogeology of the Gippsland Basin will be presented, with particular reference to the current utilisation of the groundwater resource, location of aquifer recharge areas and the impacts of falling water levels throughout. Issues such as the overall groundwater resource, risk of coastal subsidence, and concepts for the management of the large potable groundwater resources of Gippsland will be discussed.

• November 16, 2004

  AGM followed by Chairman's Address and Dinner

  Dr Ben Collingwood – Chairman’s Address – MCG Redevelopment: Design and Construction of Piled Foundations and Retention Systems

  The MCG Redevelopment project involves the demolition and reconstruction of over half of one of Melbourne’s most iconic structures. It has involved the design and construction of around 250 No. bored foundation piles for axial loads of up to 30,000 kN and lateral loads of up to 3000 kN in ground conditions featuring predominantly mudstone, with sometimes eventful incursions into dykes and collapsing sands. In addition, around 1 km of basement retention piling, including cantilever walls of up to 7m in height, has been designed and installed to retain sensitive site features including light towers, crane bases, key CBD services and the sacred turf of the playing field itself. Since the projects commencement in 2002 the many engineering challenges have interwoven themselves with some memorable on-field events, resulting in a professional experience to remember.

  Associate Professor Roger Hughes – Annual Dinner After Dinner Presentation – The Rational Motion of Crowds

  The systematic study of the motion of a crowd developed after WWII when it was realised, contrary to popular belief, that crowds behaved rationally. This talk will outline some applications of analytical techniques for predicting the behaviour of crowds. Applications discussed will include a discussion of the outcome of the Battle of Agincourt 1415, the stoning of columns on the Jamarat Bridge near Mecca, and New Year's eve celebrations in Hong Kong.