Evolution of geotechnical risk analysis in North American practice - Risk and Reliability in Geotechnical Engineering - page 476

probability of system failure is given by the case of perfect dependence among all the
probabilities; that is, for the case in which, if one mode fails, all of them fail. The
so-called De Morgan bounds have been suggested for this problem, but they are too
broad.
12.11 ConCluDIng thoughtS
Recent years have seen a chronicling of the important insights and open questions about
risk analysis, in general (Greenberg et al. 2012), and about risk in geotechnical practice, in
particular (Christian and Baecher 2011).
What are the transformative insights about geotechnical risk and reliability that have
shaped our current understanding? There are several, but we will not attempt a tentative
list here, that await another opportunity to do so; it would be with the understanding that
everyone working in the field will have his or her own list, and that not everyone will agree
with our list.
Among the insights that we consider the most transformative (in no particular order) are
(1) the understanding that geotechnical properties are spatially variable, and this variabil-
ity controls engineering performance in subtle ways; (2) the distinction between aleatory
and epistemic uncertainty is fundamental to practice, and this necessitates a conclusion
that geotechnical reliability is fundamentally Bayesian; and (3) the observation that varia-
tions in geotechnical data arise from a host of sources, and the source of the variation
dictates how the corresponding uncertainty affects our predictions. One might also draw
conclusions about models, methods, and approaches, but they, too, will wait for another
opportunity.
aCknoWleDgMentS
The authors acknowledge the valued advice and suggestions of their colleagues Robert Patev
of the USACE on the risk analysis of New Orleans post-Katrina, Robert Gilbert of the
University of Texas on developments in offshore engineering, Herbert Einstein of MIT on
developments in rock mechanics and mining, and W. Allen Marr of Geocomp Corporation
on active risk management.
reFerenCeS
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