Load and Resistance Factors for External Stability Checks of Mechanically Stabilized Earth Walls

Abstract

The use of load and resistance factor design (LRFD) to design geotechnical components of transportation infrastructure in the United States is now mandated by the Federal Highway Administration (FHWA). The advantages of LRFD over working stress design (WSD) may lead to its gradual adoption in geotechnical design even in the absence of any mandates. If load and resistance factors are based on reliability analysis, a mechanically stabilized earth (MSE) wall may be designed to a target reliability index (or a target probability of failure). Load and resistance factor design of MSE walls must consider multiple ultimate limit states, associated with both external and internal stabilities. This paper develops factors for use for the two ultimate limit states, sliding and overturning, used in design that are related to the external stability of MSE walls. Equations that closely reproduce the ultimate limit states with as little uncertainty as possible are proposed. The uncertainties of the parameters and the transformations for ultimate limit state equations are assessed using data from an extensive literature review. The first-order reliability method (FORM) is then used to produce resistance factor values for each limit state for different levels of target reliability index.