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 K-0 consolidation, the liquefaction resistance of Ottawa sand deposited underwater can (1) decrease by 50%-80% as the major principal stress direction moves away from the vertical with sigma(2)' = sigma(3)', or (2) increase by 200% to 380% as sigma(2)' increases while sigma(1)' remains vertical depending on the liquefaction criterion (strain levels). When the stress state defined by the imposed boundary condition deviated from axisymmetric compression, the combined effect on the liquefaction resistance was governed by principal stress rotation. (C) 2022 American Society of Civil Engineers.