Computational Tools for the Analysis of Stability of Embankments in Frictional-Cohesive Soils

This paper presents a series of computational tools for quick estimation of factors of safety and critical circular failure surface location for embankments. The embankments are assumed to be made of homogeneous frictional-cohesive dry soils, obeying a linear Mohr-Coulomb shear strength criterion. Cases of a firm horizon that the failure surface cannot cut through are considered to exist at the base of the embankment or at great depth. The latter case corresponds to the case of a slope in homogeneous soil. Dimensionless functions defining the factor of safety and position of the critical failure surface are constructed using the Bishop method of slices in the commercial limit equilibrium software SLIDE. Results are implemented in a computer spreadsheet that is made available for free downloading. Formulas for quick evaluation of factors of safety are also presented. The effect of the cohesion and friction angle of the soil and the position of the firm horizon on the resulting factors of safety and depth of the failure surface are discussed. An application example solved with the proposed tools and with the shear strength reduction technique implemented in the commercial software FLAC is presented. Although the tools provided in this paper have been developed for teaching basic slope stability analysis in an undergraduate soil mechanics course, the tools could be useful when performing preliminary estimates of factors of safety of embankments in actual geotechnical design practice.