Highway Embankment Failure on Soft Clay: Bad Input = Bad Output

Our ability to analyze and compute 2D and 3D factors of safety for embankments and slopes, including finite element and finite difference analyses, has increased greatly in the last decade. However, use of these analyses still requires a good understanding of soil mechanics, a reasonable range of input parameters, potential failure modes, and strain incompatibility between any dissimilar materials involved. Embankment designers should also understand the intricacies of the analytical methods being used and not consider them an accurate solution. This article presents a case history where all of these factors came into play and presents recommendations for selecting ranges of material properties, addressing strain incompatibility, and consideration of potential failure modes before initiating an engineering analysis.