Australian Geomechanics Society Sydney, New South Wales – 2010 Meetings
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10 February 2010
The 2010 Poulos Lecture : Modelling of Erosion
Prof. David Muir Wood, University of Dundee, Scotland
Following the discovery of sinkholes in the WAC Bennett Dam, British Columbia, in 1996, investigations showed that there had apparently been movement of fine material out of the core of the dam. The internal erosion (suffusion) is caused by continuing slow seepage but the concern is for the long term mechanical consequences. In order to be able to predict the result of such movement of material, a class of soil model is required which is able to accommodate changes in both density and grading of the soil. An outline of features of the Severn-Trent sand model – which incorporates effects of density variation – is presented and a suggestion is made for ways in which this model might be extended to include effects of changing particle size distribution. The modelling of erosion (narrowing grading) is complementary to the modelling of effects of particle breakage (broadening grading): simulations for both are shown and remaining uncertainties identified.
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10 March 2010
E.H. Davis Memorial Lecture
Recent Advances in the Application of Vertical Drains and Vacuum Preloading in Soft Soil StabilizationProf. Buddhima Indraratna
Over the past 15 years, Prof. Buddhima Indraratna and his co-workers have developed numerous experimental, analytical and numerical approaches that simulate the mechanics of prefabricated vertical drains (PVD) and vacuum preloading including both two-dimensional and three-dimensional analyses and more comprehensive design methods.
This lecture presents an overview of the theoretical and practical developments and salient findings of soft ground improvement via PVD and vacuum preloading with applications to selected case histories in Australia, Thailand and China.
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14 April 2010
The NSW Research Award: Advanced research in Geotechnical Engineering
Analytical and Numerical Studying of Disturbance and Pore Pressure in Soft Cohesive Soils Associated with the Installation of Mandrel-driven Prefabricated Vertical Drains — Ali Ghandeharioon
This research investigates the installation of mandrel-driven PVDs and the associated disturbance in cohesive soils using a novel elliptical cavity expansion theory validated by laboratory experiments and numerical modelling. The pattern of the disturbed region surrounding the mandrels and the distribution of stresses in soils obtained from the analytical and numerical predictions are shown to be in agreement with the results of the laboratory tests. A number of case histories are also analysed to evaluate the associate soil disturbance during the installation of the mandrel-driven prefabricated vertical drains.
Confined comminution of granular materials: self-organisation, attractors and patterns — Oded Ben Nun
In this research a novel dynamical systems approach is used to study the micro-mechanics of confined comminution, the process of size reduction, of granular systems looking at the grain scale processes driving the evolution of grain crushing. This study examines the evolution of grain size distribution and contact force distribution in the context of self-organisation and attractors. A 2D model of grain crushing based on the discrete element method (DEM) is developed; which is aimed at identifying the physical conclusions that are beyond the details of any specific model.
Constitutive modelling of partially saturated soils — Annan Zhou
This research presents a new method to couple the hydraulic component with the mechanical component in a constitutive model for unsaturated soils. Generalised constitutive relations on coupled hydro-mechanical behaviour are introduced. These generalised constitutive relations are then incorporated into existing mechanical and hydraulic models for unsaturated soils. Numerical examples are presented to show the performance of the proposed model in predicting soil behaviour along drying and loading paths. Finally the model is validated against experimental data for different soils.
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May 12, 2010
A Practical Guide to Abandoned Mine Subsidence Assessment and Mitigation
David Knott
Mine subsidence can take the form of sinkholes or troughs depending on mining and geologic conditions. Examples of the geology, mining, and subsidence features encountered in core and on the surface from US Bituminous Coal fields, particularly in the widely mined Pittsburgh Coal Seam; the Anthracite Coal field of north-eastern Pennsylvania; and the Sydney Basin, particularly the Borehole Seam, will be illustrated. The importance of understanding the mining and geology with respect to expected subsidence conditions and interpretation of investigation results will be stressed. Guidance on sinkhole development criteria and trough subsidence deformations will be provided. Finally mitigation options, such as grouting will be reviewed.
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June 9, 2010
Ipswich Motorway Upgrade, Dinmore to Goodna: Remediation of Abandoned Coalmines
Barry Land & Bill Holz
At $2bn the Ipswich Motorway, D2G Upgrade southwest of Brisbane is the largest federally funded project in QLD. The 8km section of road, Queensland’s busiest, crosses three abandoned coal mines worked at various times between the late 1800s and the 1980s.
Following investigation and analysis of the stability of each of the mines the decision was taken to fill them to ensure long term stability and safety for the road using public, the works being carried out on a sub-alliance basis to the main alliance. Each mine provided differing scenarios of geometry, depth, documentation and groundwater/methane filled mine void. Remediation procedures were developed and implemented for each mine. The D2G project is the largest abandoned mine infilling project to have taken place in Australia and provided a number of challenges and innovative solutions, including:
- Investigation of non-documented mine workings
- Stability analysis and assessment
- Groundwater Management
- Methane Management
- Target drilling
- Mapping through the use of down hole cameras.
- Sub-alliance delivery to provide value for money
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June 21, 2010
Concepts & Parameters Related to Ground Improvement Illustrated by Case Histories
Serge Varaskin
Synopsis of June 21 Presentation
The International Society for Soil Mechanics and Geotechnical Engineering (ISSMGE) Technical Committee on Ground Improvement, has proposed a classification system of ground improvement techniques according to the general nature of the soil, (frictional or cohesive) and the inclusion or not of added material (http://www.bbri.be/go/tc17). This classification system has been detailed in the state of the art report on construction methods at the Alexandria ISSMGE Conference last October. On the basis of this classification system, selected case histories from around the world will be presented highlighting the initial concept and the relevant parameters for design, quality control and acceptance of the ground improvement works.
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July 14, 2010
Next Generation of Unsealed Roads
George Vorobieff
Low volume rural roads are typically unsealed roads and numerous Australian and international studies have been carried out to improve their durability and reduce dust. New products and equipment have been produced and tested, and unfortunately many of these new products are typical promoted by the so called ’snake oil’ salesman. The goal of the salesman is to sell more product and that equates to more profit, but a holistic approach to the Shires long-term needs are never considered.
A new approach has to be taken where any unsealed road maintenance incorporates the opportunity to incrementally strengthen the pavement, reduce maintenance frequency, improve drainage and reduce the use of depleting quarried sources. At the same time rural communities need and expect safe mobility between homesteads and township, and whilst rural road users desire a sealed road, Shires have limited road funding to build and maintained sealed roads.
The next generation of unsealed roads is to look at an interim or staged approach to unsealed roads where the existing pavement and formation materials are enhanced through stabilisation using conventional binders rather than ’snake oils’. New design methodologies are being developed based on recent research trials, and the presentation will cover the current results being collected at various trial sites.
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August 11, 2010
Highly Constrained Railway Widening Project within a Previously Unrecorded Diatreme at Hornsby, NSW
Ben Rouvray & Greg Kotze
As part of the NSW Government’s Rail Clearways Program, GHD Geotechnics was the detail designer for the Hornsby Platform 5 and Stabling Project that was highly commended at the 2009 Engineering Excellence Awards. This case study relates to the widening of an existing railway embankment that is over 100 years old, under live rail traffic, located within a tightly constrained urban environment.
During the development of the detail design it became apparent that the subject site was significantly constrained by the existing embankment condition and adjacent development. These constraints prompted further detailed geotechnical investigations that revealed that the site overlies a previously unrecorded diatreme or volcanic vent.
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August 30, 2010
Rock Mass Characterization: a vehicle to translate geology into the design of engineering structures
Dr Paul Marinos – The 2010 Jahns Distinguished Lecturer
Since the attempt by Terzaghi in 1946 to describe the characteristics of rock masses, numerous rock mass classifications have been developed. Hoek and Brown (1980) set out to develop a failure criterion and a classification system, the Geological Strength Index (GSI), specifically for the purpose of designing tunnels, slopes or foundations in rocks. Here the geological character of rock material, together with a visual assessment of the mass that forms, are used as a direct input for the selection of parameters relevant for the prediction of rock mass strength and deformability. GSI has considerable potential for use in rock engineering because it permits the manifold aspects of rock to be quantified, enhancing geological logic and reducing engineering uncertainty.
A detailed description of GSI is presented with suggestions for its use and discussion on its limitations. A number of examples from designs of engineering structures conclude the presentation.
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8 September 2010
Young Geotechnical Professionals Night
Various
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13 October 2010
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10 November 2010
Chairman's Address
Mark Adams