Undrained Behavior of Silty Sand and the Role of Isotropic and K0 Consolidation

The characteristic features of undrained behavior of a silty sand are investigated for a range of initial conditions (e,p′) for both isotropic consolidation (CIU) and K0 consolidation (K0U). The silty sand contains approximately 10% natural fines. The steady-state line (SSL) for K0-consolidated specimens is slightly below the SSL for isotropic consolidated specimens. The so-called reverse behavior for silty sand is not observed for CIU, although it is observed in some cases for K0U. Earlier studies claimed that the shape and location of the consolidation line with respect to the SSL can explain such behavior. The findings of this study suggest that the liquefaction potential, a key parameter for observing reverse behavior, depends on the state of the soil and shows a unique relation to the state parameter (ψ) irrespective of the type of consolidation. However, the stress ratio at the triggering of liquefaction, ηIS, and liquefaction resistance, qIS, show slightly different relationships with ψ for isotropic and K0 conditions. This finding has practical importance for estimating liquefaction strengths, triggering of liquefaction, and developing a ψ-dependent constitutive model both for isotropic and K0 consolidation.