Experimental Studies and Constitutive Modeling of Static Liquefaction Instability in Sand–Clay Mixtures

Abstract

This paper examines static liquefaction phenomena in sand–clay mixtures from both experimental and theoretical perspectives. Consolidated undrained triaxial tests (CU tests) are implemented on a mixture of sand and clay to study the effects of initial relative density, confining pressure, and clay content on static liquefaction responses. By using the equivalent granular state parameter, a state-dependent hardening plasticity model is proposed to reproduce mechanical responses, as well as to replicate the observed static liquefaction phenomenon. In accordance with the second-order work theory, the criteria for predicting the potential instability and static liquefaction of sand–clay mixtures are obtained. The analyses show that (1) static liquefaction is prone to be promoted by low initial relative density and confining pressure; (2) even a small amount of clay particles can significantly increase the liquefaction susceptibility in loose sand–clay mixtures; (3) the proposed constitutive model can provide a satisfactory match between the test data and the simulations; and (4) even when the state of the soil is potentially unstable, soils can still remain stable unless second-order work vanishes, which indicates the inception of static liquefaction.