Analysis of reinforcement options for a partially saturated slope

The paper deals with a partially saturated natural steep slope recently failed due to rainfall. The slope response to rainfall was analyzed through advanced FEM-based seepage analysis and limit equilibrium stability analysis. Both the original configuration of the slope and a series of engineered configurations were examined. All of the remediation work options included slope reshaping, use of coarse-grained material, and installation of geogrids in different arrangements. The results of both seepage and stability analyses allowed obtaining a performance model of the slope (natural or engineered) against rainfall of different intensity-duration features and for different return periods, also taking into account different initial conditions related to the season. It was outlined the importance of unsaturated conditions, and that critical conditions for the natural slope occur for rainfall with return periods (T) not larger than 50 years and duration of 3-12 hours. Conversely, the engineered slopes perform better due to the inclusion of tensile-resistant materials like geogrids, for the presence of coarse-grained material used for slope reshaping, which also allows a better interaction of the slope with the atmosphere, globally reducing the pore water pressures in the slope and increasing the factor of safety, independent of rainfall duration-intensity.