Experimental investigation of liquefaction characteristics of saturated coral sand subjected to complex cyclic stress paths: Effects of loading frequency

How cyclic loading frequency affects the liquefaction characteristics of saturated coral sand was investigated by performing undrained cyclic shear tests subjected to a 90° jump of principal stress, with consideration given to cyclic stress ratios (CSR) of 0.25, 0.30, 0.35, and 0.40, orientations of major principal stress of 0°, 22.5°, 45°, 67.5°, and 90°, and cyclic loading frequencies ( f ) of 0.05, 0.1, 0.5, and 1 Hz. The test results show that increasing f decreases the generation rate of excess pore water pressure and deformation. Under the same cyclic stress path, the amplitude of deviatoric strain and the excess pore water pressure ratio (ru) have a unique relationship. The unit cyclic stress ratio (USR) was introduced to represent the liquefaction resistance of saturated coral sand under different cyclic loading modes, and increased f leads to increased liquefaction resistance. Under isotropic consolidation, the relationship between the cumulative dissipated energy (Wc) and ru is almost independent of f, CSR, and cyclic stress path. A hyperbolic function model of Wc with the development of ru is proposed, and its applicability is verified against data from the literature.