| A methodology to evaluate the reliability of geotechnical systems considering the presence of geological anomalies is developed. The proposed methodology consists of three major tasks: (i) modeling of the anomaly uncertainties and developing subsequent methods to assess their statistics, (ii) evaluating the effect of the different anomaly configurations on the geotechnical system performances, and (iii) incorporating the uncertainties of both the anomaly and analytical model parameters, namely soil and load properties, into a systematic reliability evaluation. Based on Bayesian theory, methods are developed whereby the statistics of anomaly properties can be assessed from previous experience updated by observations from additional site exploration programs. Furthermore, the effect of anomalies in the geotechnical system performance is evaluated using empirical response surface functions of anomaly characteristics. And finally, the performance reliability can be predicted by combining these components.; The methodology is applied to the settlement performance of a 100 ft. {dollar}times{dollar} 100 ft. raft on either clay or sand deposits where a pocket of soft soil material may exist. It is also then applied to the short term slope stability problem for a 30 ft. high clay embankment where a soft soil pocket or a thin clay seam may be present. This study shows that the possible presence presence of geologic anomalies can reduce the reliability of the geotechnical systems significantly depending on the anomaly characteristics and the probability of anomaly presence; and hence, further design measures can be devised accordingly to increase the performance reliability. The proposed reliability method will also help to choose an exploration scheme that can delineate the uncertainties of anomaly more effectively, and thus further facilitate the planning of the optimal site exploration strategy. To assist those engineers with little or no training in probability and reliability analysis, a prototype Knowledge-Based Expert System (KBES) is developed. The KBES could serve to assist engineers in planning their site exploration program and subsequently evaluating the geotechnical system reliability, while allowing them to input their engineering judgment in a user-friendly environment. |
