Number 17 – Editorial and society news

First a brief comment about the special edition of ‘Australian Geomechanics’ covering the 5th Australia New Zealand Geomechanics Conference. This edition was prepared by the conference organizing committee chaired by Prof. Harry Poulos and saved the current editorial committee many hours of painstaking work. Thank you Harry, John and Garry.

The task of drawing suitable material together for this issue of ‘Australian Geomechanics’ proved more difficult than anticipated. Striking a balance on what to publish is often complicated when material arrives which is considered borderline or which is not in accordance with our adopted 52 character column width. Even though the publication policy of ‘Australian Geomechanics’ has been enunciated regularly, submissions are still received which are too detailed and heavy going for a ‘news’ type publication like this.

A request for more articles on mining and related matters is slowly starting to bear fruit. As our mining colleagues form a very significant proportion of our Society, their interests should be catered for more regularly.

The cover of this issue shows some aspects of the ‘Briseis’ (Cascade) Dam, in Northern Tasmania, which failed 60 years ago, resulting in the loss of fourteen lives. This dam failure provides a forceful reminder of the dangers associated with designing and building Geotechnical Structures. This is especially so when designs are, or have to be, based on ‘insufficient’ or ‘limited’ knowledge and understanding. This can often be the case when large structures such as dams are built in environments which can not be considered to be fully defined. Perhaps the only lower limit of a parameter that we can really be sure of is zero for the saturated cohesion intercept.

This brings us to the issue of professional liability which is currently being debated in many quarters. Dr Peter Miller, in his regular column in ‘Engineers Australia’ constantly reminds his readers of the implications of current legal ‘opinion’ on the application of the laws of liability. Many of his recent contributions to this debate should come as disturbing news to those engaged in the design, construction or maintenance of geotechnical structures. Miller concludes one of his recent columns “Engineers do not know it all” with the words: ‘Engineering decision making is facing a crisis, and we are moving towards a dialogue which has been looming for some time. It will go to the root of the relationship between the profession and the community. Before we embark upon it, let’s take a deep look at ourselves’.

The above words are most pertinent to Geomechanical experts, be they Engineers or Geologists, as we almost daily evaluate uncertainties of design and probabilities of failure. Although advances in our knowledge and understanding of structural behaviour of materials may have led to considerable improvements in performance and safety, this does not mean that the risk of failure can be completely eliminated. This is of course generally recognized within the profession and is often expressed in concepts such as ‘State of the Art’ ‘Failure Criteria’ and ‘Acceptable Risk’. Unfortunately such concepts are often difficult to quantify and are also subject to continual change. This is reflected for example in the fact that many water authorities both in Australia and overseas have during this decade been very much preoccupied with the issues of Dam Safety and spillway capacity. In this process many structures have now been identified which are considered to be unsafe and in particular to have inadequate spillway capacities. The process of bringing such structures to a currently ‘acceptable’ standard often requires considerable time in planning, design and construction. Any questions regarding liability in the event of a mishap occurring before the completion of an upgrading programme are likely to be complex.

News items and articles describing ‘mishaps’ and ‘foul-ups’ appear quite regularly in technical journals and form a constant reminder of how things can and do go seriously wrong. Some of these ‘failures’ such as Malpasset, Vajont and Teton, to name but a few, are permanently engrained in our minds. Many others may not be so well known but all form part of a pool of bitter experience. With the aid of hindsight the flaws in the original design decisions may be obvious. However in many instances the original design decisions appeared to be quite reasonable, when judged by the standards of the day. Then there are areas where the standards of design for some structures have changed to such an extent that it is hard to believe that those structures could have stood the test of time. In other cases disaster may appear to have been averted more by luck than good design.

Besides continually reminding ourselves of the ‘failures’ and ‘incidents’ in our specific fields of endeavour, we should perhaps also keep in mind the following dictums:

“Redundant structures can generally only accommodate one under-designed component” and “the expansion of liability is probable, for deep pockets attract litigation.”

In closing this editorial we thank the Hydro-Electric Commission for its assistance in producing this issue.