Engineers Australia

Estimating the Mechanical Properties of Rock Masses: Reflections on a career in Rock Mechanics

Emeritus Professor E T (Ted) Brown AC

As a civil engineering student at the University of Melbourne in the late 1950s, the speaker naturally gravitated towards a specialisation in geomechanics (although the term wasn’t in use then), largely because of the influence of an inspiring undergraduate teacher and subsequent post- graduate supervisor, Professor Hugh Trollope. Partly as a result of having been brought up in a mining family in central Victoria, and partly because of an interest in the major infrastructure projects underway at the time, most notably the Snowy Mountains Hydro-electric Scheme, he soon decided to specialise in rock mechanics and rock engineering, although not to the total exclusion for many years of his original discipline of soil mechanics. The topic on which he worked for his PhD in the mid-to late 1960s remains at the core of his work as a consulting engineer today, although there have been a number of excursions in other directions, including into university management, along the way.

Reliably estimating the mechanical properties of discontinuous rock masses remains one of the greatest challenges faced in the discipline of rock mechanics. This lecture will discuss the development, uses and limitations of the Hoek-Brown empirical rock and rock mass strength criterion, some of the extensions made to the criterion by others, and associated methods of estimating rock mass deformabilities. Extreme care must be taken in extending the use of these approaches beyond reasonable limits. Modern methods of predicting the engineering responses of rocks and rock masses using advanced numerically-intensive methods provide a sound and promising basis for developing improved understandings of the engineering responses of rock masses and for making improved predictions of rock mass properties and performance.

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