Undrained cyclic behavior of loose sand under anisotropic consolidation

Abstract

This paper presents an experimental study of the liquefaction behavior of sand under initial shear conditions. The emphasis of the study was placed on loose sand by using cyclically loaded triaxial tests, where sand specimens were subjected to anisotropic consolidation to arrive at different levels of static shear stresses before the application of cyclic loading. The study reveals that a small static shear applied in compression is beneficial to liquefaction resistance but high levels of initial shear stress may become a detrimental factor. It is proposed that a threshold initial shear stress level above which cyclic resistance starts to drop exists in loose sand. Compared with an initial shear applied in compression, an initial shear stress applied in extension is found to impose a contrasting behavior such that increasing the initial shear stress level always reduces the cyclic resistance. This behavior is considered to be the result of the enhanced contractiveness of sand in extension.