Updating anomaly statistics—single anomaly case

Abstract A geologic anomaly is formed by any foreign material not included in the design soil profile. The performance of a geotechnical system could be significantly affected if the size of an anomly is sufficiently large. However, the presence of such an anomaly and its size can never be fully predicted. The probability of anomaly presence and its probable size distribution may be assessed on the basis of the engineers' experience and judgment, supplemented with the encounter history from exploratory borings performed at the site. A method for updating the probability of anomaly presence and the anomaly size distribution, based on this information, is formulated. The effectiveness of using an extensive boring program in limiting the likelihood of anomaly presence and, if present, in limiting the anomaly to acceptable size, is found to depend on boring grid patterns, the density of borings per unit area, and prior estimates of anomaly size and anomaly presence probability.