This white paper presents the results of a survey initiated by the Committee on Materials for Embankment Dams to determine the “state of the practice” for selecting fill strength parameters used in static and pseudostatic analyses of earthfill embankment dams. A
questionnaire was sent to federal and state agencies, consulting firms, and private consultants experienced in the design and safety evaluation of embankment dams. Among the federal and state agencies contacted were: U. S. Army Corps of Engineers(USACE); U. S. Bureau of Reclamation (USBR); Federal Energy Regulatory Commission (FERC); U. S. Department of Agriculture, National Resources Conservation Service (NRCS); Tennessee Valley Authority (TVA); and California Department of Water Resources, Division of Dam Safety (DSOD).

The questionnaire asked each respondent to provide information as to their practice in determining the static strength of embankment materials and analyzing the static stability of embankment dams. The information provided included: approach to static stability analyses, loading conditions, shear strength parameters, field and laboratory testing used to determine shear strength parameters, procedures for interpreting test results, factors of safety, and methodologies used for static analyses.

The information provided by the respondents is summarized in this white paper, which is divided into the following sections:
~ Loading Conditions for Embankment Dams, including End of Construction, Steady-State Seepage, Rapid Drawdown, and Earthquake.
~ Determination of Shear Strengths, including subsections describing total and effective stresses, selection of shear strengths, and the use of cohesion. The information provided in this white paper regarding the determination of shear strengths applies primarily to earthfill materials: soils with a grain size less than 20 mm.
~ Static Analyses of Embankment Stability, including subsections on the limit equilibrium method of slope stability analysis, types of potential failures surfaces evaluated, location of potential failure surfaces for analyses, and recommended factors of safety.