Factor of Safety Reduction Factors for Accounting for Progressive Failure for Earthen Levees with Underlying Thin Layers of Sensitive Soils

Adam J Lobbestael,Josh Colley,Adda Athanasopoulos-Zekkos

doi:10.1155/2013/893602

Adam J Lobbestael, Josh Colley + Show 1 more

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https://doi.org/10.1155/2013/893602

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Abstract

The effects of progressive failure on flood embankments with underlying thin layers of soft, sensitive soils are investigated. Finite element analysis allows for investigation of strain-softening effects and progressive failure in soft and sensitive soils. However, limit equilibrium methods for slope stability analysis, widely used in industry, cannot capture these effects and may result in unconservative factors of safety. A parametric analysis was conducted to investigate the effect of thin layers of soft sensitive soils on the stability of flood embankments. A flood embankment was modeled using both the limit equilibrium method and the finite element method. The foundation profile was altered to determine the extent to which varying soft and sensitive soils affected the stability of the embankment, with respect to progressive failure. The results from the two methods were compared to determine reduction factors that can be applied towards factors of safety computed using limit equilibrium methods, in order to capture progressive failure.

Highlights

The design and construction of levee systems are often challenging tasks due to the complex nature of the geologic conditions that typically comprise the site of a levee or flood embankment
The analyses performed in this study indicate that the peak shear strength and sensitivity are the most influential parameters with regard to progressive failure
A parametric analysis was conducted to investigate the effect of thin layers of soft, sensitive soils on the stability of flood embankments and to propose factor of safety reduction factors that can be applied to factors of safety computed using limit equilibrium analysis

Summary

Introduction

The design and construction of levee systems are often challenging tasks due to the complex nature of the geologic conditions that typically comprise the site of a levee or flood embankment. This complex geology is the result of the processes of deposition and erosion that take place along coasts and riverbanks. The peak shear strength throughout the developing sliding surface is not simultaneously mobilized because the shear stresses that develop within sensitive soils are highly strain dependent. The alternative approach, using residual shear strengths in design, has proven to result in an underestimation of the factor of safety [8]

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