The residual shear strengths of saturated sandy and silty soils are often estimated from the relationships between insitu penetration resistances and residual shear strength obtained from the back analysis of post failure geometries of embankments that suffered varying degrees of distress resulting from static rapid (undrained) loading. The procedures for back analysis employed so far do not account for viscous drag and strain energy. A simple procedure has been proposed herein approximately accounting for viscosity and strain energy. The results from back analysis of ten flow failure case histories using the proposed energy approach were used to develop a correlation between residual shear strength and Standard Penetration Test (SPT) blow counts.