Site Exploration Strategy for Geologic Anomaly Characterization

A geologic anomaly is any inclusion that is of a different material type or has different physical properties from that included or normally expected in a design profile. The performance of a geotechnical system could be significantly affected if the anomaly has undesirable properties. However, the presence of such an anomaly and its properties can never be ascertained. Methods for updating the anomaly location and size distributions and the probability of anomaly presence based on the engineer's experience and judgment, supplemented with the encounter history from exploratory borings performed at the site, are formulated. The effectiveness of using an extensive boring program in limiting the likelihood of anomaly presence and, if present, in limiting the anomaly size and location, is found to depend on the overall probability of anomaly detection by the exploration scheme, and prior estimates of anomaly properties and anomaly presence probability. The updated anomaly location and size distributions provide valuable input data for a reliability evaluation of the geotechnical system.