Soil Databases to Assist Slope Stability Assessments in the Eastern Caribbean

Rainfall-triggered landslides are an ‘everyday risk’ to Small Island States, such as Saint Lucia in the Caribbean, and have the potential to destroy or damage buildings and disrupt lifelines such as roads and pipelines. To better evaluate these landslide hazards, efforts have been made to develop decision-support tools linking rainfall scenarios to stability for different types of road cut slope. Many thousands of stochastic simulations can be performed using a combined hydrology and slope stability model (CHASM) which requires inputs of slope cross-sectional geometry, soil and hydrological parameters which allows representative rainfall-triggered landslide scenarios to be produced. To use CHASM for this purpose the statistical variation of the relevant geotechnical properties such as friction angle needs to be assessed. This paper presents the analysis of an updated database for Saint Lucian soils that has been compiled using data supplied by the Government of Saint Lucia Ministry of Infrastructure, Port Services and Transport. The Coefficient of Variation values of the key soil mechanics parameters are reported and previously developed transformation models for estimating effective friction angle are updated. The Weibull statistical distribution is shown to be the best fit to the friction angle data.