Slope Failure Probability Under Earthquake Condition by Monte Carlo Simulation: Methodology and Example for an Infinite Slope

A new approach in evaluating the slope failure probability under earthquake condition was proposed in this study. Unlike the use of a deterministic seismic coefficient in a pseudostatic analysis, the uncertainties of earthquake magnitude, location, frequency, and seismic-wave attenuation were taken into account in the new approach. The probability distributions of the earthquake parameters follow those described in probabilistic seismic hazard analysis (PSHA). Along with the considerations of the uncertainties of slope parameters, such as slope angle, slope height, and soil/rock properties, the slope failure probability can be estimated by a probabilistic analysis. In particular, the new approach used Monte Carlo simulation (MCS) in the analysis, in which random parameters were generated with prescribed probability distributions and statistics. With an n-trial MCS being performed, slope failure probability is equal to the ratio between the trial of slope failure and total trials. In this study, the approach was also demonstrated by a benchmark PSHA example integrated with a hypothetical infinite slope. For such a slope under the setup of seismicity, its failure probability increased to 8.3% in a 50-year condition, from 0.16% in a one-year condition. The increase in slope failure probability resulted from a higher earthquake frequency with respect to a longer duration of interest.