Multimodal reliability analysis of 3D slopes with a genetic algorithm

This paper presents a genetic algorithm (GA) to solve the multimodal optimisation problem resulting from 3D slopes prone to multiple regions of failure. A probabilistic approach is taken by using the first-order reliability method (FORM) to approximate the probability of failure. The 3D Bishop method is selected but can be replaced as appropriate. Since 3D analyses have higher computational costs than 2D simulations, we demonstrate that the FORM approach is very practical to large-scale geotechnical problems compared to alternatives such as Monte Carlo simulations (MCS). Furthermore, we show that the GA optimiser can obtain reliability indices and find critical failure regions that would not be found by the MCS easily. These characteristics are demonstrated by some simple test cases and the more complex topography of the Mount St. Helens in the USA.