Abstract: The influence of cyclic loading frequency f on the liquefaction behaviors of saturated quartz sands during undrained cyclic laboratory tests has been investigated extensively, but rare studies reported on the effect of f on the liquefaction behaviors of saturated coral sands. To better understand the effects of the f on the liquefaction behaviors of saturated coral sand, a series of undrained cyclic shear tests is performed on isotropically consolidated, medium dense saturated specimens subjected to the 90º jump of principal stress in the range of f = 0.01−1.0 Hz. For all loading patterns investigated, the growth rates of the excess pore water pressure ratio ru and the generalized shear strain γ_g decrease with the increase of f; the number of liquefaction NL required to cause the initial liquefaction increases with f; a unique tangent correlation function exists between the generalized shear strain amplitude γ_ga and the peak excess pore pressure ratio rumax (r_umax is independent variable); and an increase in f weakens the dilatancy of the specimen. By introducing a unit cyclic stress ratio USR as a proxy for cyclic stress level acting on the specimen during the cyclic testing, USR versus N_L curves moves to the upper right with f, a unified form of power-law function of the correlation exists between USR and N_L regardless of f. This indicates that liquefaction resistance of saturated coral sands increases with f.

Key words: saturated coral sand, liquefaction behavior, loading frequency, cyclic loading pattern, liquefaction resistance