John Jaeger Memorial Award Lecture: Predicting the Mechanical Behaviour of Structured Soils

Professor John Carter

Abstract

Many naturally occurring sedimentary soils and most residual soil deposits are known to possess some form of structure, which enables them to behave differently from the same material in a reconstituted state whenever subjected to mechanical loading. An important feature of the mechanical behaviour of structured soils is the occurrence of a destructuring phase associated with loading, during which the initial soil structure may be partially or completely lost. In extreme cases, the mechanical response of such soils may change from rock-like to soil-like behaviour. In particular, at some point during the loading of many of these soils a small change in the stress-state may cause very large strains. Therefore, significant inaccuracies in predictions can arise if the influence of soil structure is not considered. Indeed, under some circumstances the initial structural features of the soil may in fact dominate the subsequent engineering behaviour.

The key to obtaining accurate predictions of the mechanical response of such soils is the development and application of reliable stress-strain (or constitutive) models for these materials, and the incorporation of these models in numerical procedures used to solve the appropriate boundary value problems.

In this lecture, key elements of the behaviour of structured soils will be reviewed briefly and a class of constitutive models suitable to describe the complex behaviour of such materials will be described. Application of these models to the prediction of the bearing response of structured soils will also be described, allowing quantification of the influence of initial soil structure on the response of footings. Identification of the key engineering properties having the most influence on this response will be conducted, and ways in which such parameters may be measured in practice will be discussed.

About Professor John Carter

Professor John Carter is the former Pro Vice-Chancellor and Dean of Engineering at The University of Newcastle. In May 2013 he was appointed as an Emeritus Professor in Engineering at The University of Newcastle, where he remains as a researcher and Chief Investigator in the ARC Centre of Excellence for Geotechnical Science and Engineering. His research interests include the development and application of numerical methods in geotechnics, problems of soil-structure interaction, rock mechanics, soft soil engineering, tunnelling and the behaviour of seabed soils and foundations. He has also been involved in commercialisation of research and the marketing of its outcomes, including his own specialist geotechnical software. He is a former director of Benthic GeoTech Pty Ltd, a joint venture company that conceived, designed, built and now operates PROD, the Portable Remotely Operated Drill, which is used in water depths out to 2000 m to penetrate the ocean floor in order to conduct in situ tests and recover core samples. Until December 2013 he was a Consultant Director of Perth-based specialist geotechnical consultancy, Advanced Geomechanics. In 2006 he was appointed as a Member of the Order of Australia (AM) for his contributions to civil engineering through research into soil and rock mechanics and as an adviser to industry. John is a Fellow of the Australian Academy of Science, the Australian Academy of Technological Sciences and Engineering, the Institution of Engineers, Australia and the Australian Institute of Building. He is also a graduate member of the Australian Institute of Company Directors.

Engineers Australia members participating in AGS technical sessions can record attendance on their personal CPD logs. Members should refer to Engineers Australia CPD policy for details on CPD types, requirements and auditing guidelines.