Most geotechnical engineers feel that the undrained shear strength measured by the field vane in the surficial weathered crust cannot be fully mobilized during the failure of an embankment built of soft clay deposits. Consequently, the vane strength in the crust is generally reduced by some arbitrary means before stability calculations are performed. This paper presents the results of an experimental program aimed at evaluating the available undrained shear strength in the crust.In situshear box and plate loading tests as well as triaxial compression and extension tests indicate that the available undrained shear strength in the crust is of the same magnitude as the vane strength measured in the intact clay immediately below the crust. This paper also proposes a method to account for the effect of the embankment confinement in the central portion of the foundation. The proposed methodology is checked by a back analysis of the failure of the Olga test embankment built at Matagami, Quebec.Key words: vane test, vane test correction, weathered crust, shear box, plate loading test, embankment stability.