Lodalen slide: a probabilistic assessment

Abstract

Conventional slope practice, based on the deterministic factor of safety, cannot address the uncertainty in the input parameters of slope analyses in any explicit way. It relies entirely on the subjective judgment of the designer, which varies substantially among geotechnical engineers. Probabilistic techniques are powerful tools that can be used to quantify and incorporate uncertainty into slope analysis and design. A probabilistic slope analysis methodology based on Monte Carlo simulation using Microsoft® Excel and @Risk software is applied to investigate the Lodalen slide that occurred in Norway in 1954. Starting with field and laboratory data, the study demonstrates the techniques used in quantifying the uncertainties in soil properties and pore-water pressure, conducting a probabilistic assessment, and estimating the probability of unsatisfactory performance. The probability of unsatisfactory performance of the Lodalen slope is estimated to be 0.70, indicating that failure was imminent. The inclination of the Lodalen slope is then flattened, hypothetically, to different angles and the relationships between the slope angle, the factor of safety, and the probability of unsatisfactory performance are investigated.Key words: probabilistic analysis, slope stability, Monte Carlo simulation, spatial variability, Lodalen slide.