Embankment Slope Stability Analysis: What is Important and What is Not

In current practice, embankment stability analyses are typically performed using limit equilibrium analysis methods, as implemented in computer programs. Numerous input selections, estimates, and assumptions need to be made to complete the analyses. But which of these factors heavily influence the results and which affect the results to a much smaller degree? On which factors should the analyst concentrate most of his/her characterization efforts? The answers to these questions are explored in this paper through example analysis results.
This paper was prepared for a stability analysis mini-workshop session at the Dam Safety 2010, the Annual National Conference of the Association of State Dam Safety Officials. The session also included a companion paper by Danny K. McCook titled “Selections of Strengths for Embankment Stability Analyses.”
The following factors can all affect the results of embankment slope stability analyses:
- soil strengths
- Cross section geometry and stratigraphy
- Shear surface shape
- Internal water levels
- Soil unit weights
- Computer program
- Analysis method (Janbu, Bishop, Spencer, etc.)
- Piezometric modeling method (phreatic surface vs. pore pressure distributions)