Sydney Chapter

Be careful with reactive clays – some case histories

Bruce Walker

Abstract

Reactive clays underlie much of Sydney and the surrounding areas. Guidance for design to cope with reactive soil movements is presented in AS2870 ‘Residential Slabs and Footings’. The principles for investigation and design are well established and should be known to practicing geotechnical engineers and engineering geologists in the Sydney area.

Nonetheless, problems still occur where buildings/structures are damaged due to reactive clays. Often the damage results in litigation. This presentation will consider some example case histories where damage has occurred and the likely causes as determined by geotechnical investigations. Comment will also be given on the application of some aspects of AS2870.

About Bruce Walker

Bruce Walker has practised as a Geotechnical Consulting Engineer since graduation from Sydney University with First Class Honours in 1972. He has worked mainly in Australia, Hong Kong and United Kingdom with a number of special assignments to other places. He was a Director of Jeffery and Katauskas Pty Ltd, now JK Geotechnics, from 1988 to 2012 mainly practising in the areas of foundation engineering, including shrink-swell soils, excavation and retention, and slope stability. Bruce retired from full time work in mid-2012 and since then has been a Principal Consultant engaged on a number of commissions as an expert witness for litigation and insurance claims and for peer reviews. These commissions, and earlier commissions, included many related to shrink swell behaviour of clay soils predominantly in the Sydney region.

He was Chairman of the AGS Sydney Chapter Sub-Committee, responsible for the 1985 paper ‘Geotechnical Risk Associated with Hillside Development’, then Chairman of the AGS National Committee Sub-Committee responsible for the 2000 paper ‘Landslide Risk Management Concepts and Guidelines’ and subsequent 2002 ‘Road Show’ presentations. More recently he was the Working Group Convenor for 2007 ‘Practice Note Guidelines for Landslide Risk Management’ and participated in the Risky Roadshow in 2011 presenting the updated suite of LRM papers around Australia.

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.