Minimum Undrained Strength Versus Steady‐State Strength of Sands

Available consolidated isotropically undrained triaxial tests (CIU) on samples of reconstituted sands are analyzed in terms of the UF and LF lines to establish the conditions required to induce strain softening during monotonic loading. Tests on other sands than those tested by the writer support the view of the existence of upper and lower limits of the F line (steady‐state line), which are defined as the UF and LF lines, respectively. The minimum strength (LF line) of any sand is dependent upon the initial state. Unlimited and limited flow are observed for samples consolidated within three regions, which are defined in a state diagram. The limits between these regions appear to be related to the slope, λ, of the UF line. Finally, the value of the ratio of the minimum strength from the LF line and the steady‐state strength from the UF line is also dependent upon λ.