The Engineering Geology of the Sydney Region – Revisited

Graham Scholey and Geoff Young


In keeping with annual tradition, on 13 October 2004 the Sydney Chapter of the Australian Geomechanics Society will present its seventh Mini-Symposium, the Engineering Geology of the Sydney Region – Revisited. This volume of Australian Geomechanics Journal is dedicated to the papers that are to be presented at the mini-symposium.

This topic was previously addressed in the well-known 1985 publication on the Engineering Geology of the Sydney Region. Since 1985 the Sydney region has seen significant infrastructure development, including housing and transportation. This development has provided new opportunities for geotechnical practitioners to advance their understanding of the engineering geology and hydrogeology of the region.

The mini-symposium is intended to provide a forum for the compilation of this knowledge. Topics presented in 1985 have been supplemented with recent data and several new topics have been addressed.

Topics include a review of the engineering (Pells) and hydrogeological (Tammetta and Hewitt) properties of the Hawkesbury Sandstone and case histories demonstrating the engineering implications of variability in the Hawkesbury sandstone (Speechley, Walker and Scholey). Och, Pells and Braybrooke have used recent data to compile a map illustrating geological faults and dykes in Sydney CBD. This map will be handed out at the Mini-Symposium and it is hoped that it will be published in an later issue of this journal.

The engineering properties of the Ashfield Shale have been well documented, but the paper by William and Airey provides similar data for the Bringelly Shale, which has received greater attention as the urban development of Western Sydney progresses. Salinisation in the shales has significant impact on the urbanisation of Western Sydney and is discussed by McNally. Hatley addresses the hydrogeology of the Botany Sands.

The characteristics and engineering implications of the regional stress field are discussed in three papers (Pells, McQueen and Walker). Clearly there are differences in opinion as to the best method for making in situ stress measurements and in the equations that best model the stress field. Interested readers are encouraged to study each of these papers to understand current limitations of stress measurements and predictions.

The convenors acknowledge the contributions made by the authors and the great efforts that have been made to present information that reasonably represents the current state of knowledge. In addition, thanks are extended to peer reviewers, nominated by the authors, who have provided valuable critique.