Flowability for viscous fluid flow triggering liquefaction in saturated coral sand subjected to principal stress rotation

Abstract

The reasonable determination of cyclic resistance in saturated sand is crucial for ensuring the long-term stability of marine structures. This paper investigates the liquefaction-induced flow characteristics of saturated coral sand specimens under complex cyclic loading conditions through cyclic shear tests with varying stress paths and frequencies. Experimental results demonstrate significant differences in deviatoric strain amplitude at the initial attainment of zero effective stress under different cyclic stress paths. To characterize cyclic resistance under complex loading, we introduce the unit cyclic stress ratio as a novel index. Notably, there are substantial differences in cyclic resistance between excess pore-water pressure (u_e)-based and strain-based failure criteria across various cyclic loading modes. The specimens subjected to cyclic loading exhibit viscous fluid-like properties, leading us to propose a viscous fluid flow cyclic failure criterion within a comprehensive framework that considers both u_e and strain. For practical engineering applications, it is noteworthy that cyclic resistance obtained from the viscous fluid damage criterion demonstrates greater conservatism, thereby providing enhanced safety assurance.