Screening Geotechnical Risks

Ranking schemes are widely used to screen a large population of potentially risky situations or facilities to identify those posing the greatest risk. Examples include screening flood levee reaches, classifying damaged foundations after an earthquake, and identifying potentially dangerous areas for landslides. These problems all share the circumstance that a large number of situations or facilities need to be inspected, which prohibits a detailed engineering evaluation of each, but some level of quantitative evidence and appraisal is needed to classify each as potentially dangerous. The typical ranking scheme uses simple weighted-sum scores or sometimes a pair of simple scores for both probability and consequence of failure. The ever-popular risk matrix is an example of such a ranking scheme. However, these simple metrics often violate fundamental measure-theoretic principles and, as a result, yield risk rankings that differ from what one would obtain from probabilistic risk analysis (PRA). This does not have to be the case. Using a Bayesian Factor scheme to construct simple risk scores, one can obtain simple but proper risk rankings for flood levee screening, forensic engineering, and pit mine slope inspection that are isomorphic with PRA. Bayesian Factor Theory is explicated and practical examples of its use are presented.