The critical state line and its application to soil liquefaction

Abstract

This paper reviews some of the discussion regarding the critical or steady state line and its application in liquefaction evaluation. In particular, the approach has been criticised on the basis that a unique critical state line does not exist for sands. Once a distinction is made between transient or quasi-steady states and ultimate steady states, and appropriate consideration is given to test conditions and shear band formation, it appears that a unique critical state line can be defined for a sand. The critical state line can be used in liquefaction evaluation as a reference state, both for insitu test interpretation and constitutive modelling to determine the undrained shear strength. The undrained strength at the critical state is not necessarily the appropriate undrained shear strength.