The effect of principal stress rotation and intermediate principal stress changes on the liquefaction resistance and undrained cyclic response of Ottawa sand

In laboratory testing, the liquefaction resistance of sands is typically evaluated using cyclic triaxial and simple shear tests. These tests cannot be used in a rigorous manner to systematically assess the effects of principal stress rotation and intermediate principal stress changes on the undrained cyclic response of sands. In this study, the effect of these two factors on the liquefaction resistance of Ottawa sand was investigated using a cyclic hollow cylinder apparatus. At similar initial states of fabric and mean effective stress following K0 consolidation, the liquefaction resistance of Ottawa sand deposited underwater can: (i) decrease by 50% to 80 % as the major principal stress direction moves away from the vertical with Vc2= Vc3, or (ii) increase by 200% to 380%, as Vc2 increases while Vc1 remains vertical depending on the liquefaction criterion (strain levels). When the stress state defined by the imposed boundary condition deviates from axisymmetric compression, the combined effect on the liquefaction resistance is governed by principal stress rotation