Improving Prediction of Failure Probability at a Site-Specific Slope by Considering Its Survival Records under Past Rainfall Events

Previous studies show that the failure probabilities estimated using existing reliability methods are often overestimated more than an order of magnitude than the observed frequency, and this has been deemed as a challenging problem in geotechnical risk and reliability community. The actual failure probability is often quite small. For example, the observed annual rates of slope failure in Hong Kong were 0.041% and 0.329% for engineered and non-engineered slopes in 2020. To address this challenge, this study proposes to explicitly model landslide triggering mechanism (e.g., rainfall infiltration) and utilize the fact that an existing slope stayed stable during past rainfall events to update uncertain soil parameters for predicting the time-variant slope failure probability under a future target rainstorm. Results showed slope survival records could be utilized to reduce uncertainties in soil parameters and enhance prediction of slope failure probability in both its absolute magnitude and variation over time. © 2023 by the American Society of Civil Engineers.