Soil Shear Strength Selection for Stability Analysis - Practical Guidance

Slope stability analysis is a fundamental process in dam safety practice and requires relevant and representative shear strength characterization of both the embankment and foundation soils. Drained strengths versus undrained strengths and effective stress versus total stress analysis methods, and when to use both, are topics that often get muddled, even by experienced engineers. This paper endeavors to clarify these topics and provide practical guidance for shear strength characterization of embankment dams and their foundations under different loading conditions. A review of the relationship between fundamental stress-strain behavior and soil shear strength, and how that relationship leads to practical selection of appropriate shear strengths for stability analysis is presented. That fundamental understanding then leads into the discussion of evaluating the shear strengths of cohesionless soils (sands and gravels) and cohesive soils (clays and silts).