The drained residual shear strength of overconsolidated clays is an important parameter in assessing the stability of slopes that contain a preexisting shear surface. Laboratory Bromhead ring shear apparatus and 32 clay evaluation of drained residual shear strength in relation to clay fraction and liquid limit. A new correlation is presented that is a function of the liquid limit, clay-size fraction, and effective normal stress and can be used to estimate te entire ninlinear residual failure envelope.