Sydney Chapter

2014 AGS Practitioner Award Distinguished Lecture in Sydney

ESCAPING THE GOLDEN CAGE*

Learning to Practise the Art of Observational Geotechnical Engineering

John Simmons

Abstract

The observational method is a respected and much-quoted pillar of geotechnical practice, but it appears in many guises and its application is not always clearly understood or appreciated. At its heart is the engineer’s dilemma of getting something to work safely and efficiently in the face of uncertainties. Observational geotechnical engineering is the art of observing the realities of the working world to more fully understand the value and limitations of theory and modelling.

This presentation traces the role of observations in shaping a professional career that started with a passion for geology, dams, and bridges, developed into a fascination for slope stability and periglacial landforms, was seconded into the black arts of slope stability and waste management in coal mining, and was then driven back to research to seek better answers to some fundamental mining slope stability problems. The complex inter-relationships among assumptions, analyses, observations, and outcomes are outlined for some case histories involving pile foundations, earthfill dams, slope instability, and material characterisation tests. In order to understand and achieve well engineered outcomes, observational skill and design detailing is promoted as the key to escaping the golden cage of modelling and analysis.

(* inspired by a Karl Terzaghi quote)

About John Simmons

John Simmons has a BE (Civil) from the University of Queensland in 1971, and an MSc (1974) and PhD (1982) in Civil Engineering (Geotechnical) from the University of Alberta. After a childhood of dam building, he started his engineering career as a bridge construction worker and then specialised in field mapping of rockslides in the Canadian Rockies and landslides in suburban Edmonton. He held teaching and research positions for several years at James Cook University, including investigations of pavements, coral reef materials, soft estuarine soils, slope stability of saprolites, brittle failure of Mt Isa mine pillars, and the introduction of operational piezocone technology to Australia in 1986. From 1990 to 1995 he worked for BHP Engineering where he coordinated and supervised geotechnical projects in Australia, Algeria, Indonesia, Vietnam, and India. He was seconded to what is now BMA Coal where he shared responsibility for open cut geotechnical services for Bowen Basin coal mines. In 1995 he commenced an independent geotechnical consultancy, where his projects have ranged from bat caves to reclamations and heavy duty port pavements, slope stability and slope hazard management for open pit coal mining, foundations, dam designs and certifications, materials testing, and investigations of professional misconduct. Since 2011 he has been a conjoint fellow at the University of Newcastle where he co-supervises research and helped develop a very large high-capacity direct shear testing facility. He has written three theses based on finite element modelling of seepage, arching in earthfill dams, and the mechanics of progressive failure, and authored or co-authored over 90 publications including book chapters on tropical and residual soils and on dragline waste dump design.

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.