Influence of cyclic loading frequency on liquefaction behaviors of saturated coral sand

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 off 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 90 degrees 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 r(u) and the generalized shear strain gamma(g) decrease with the increase of f, the number of liquefaction N-L, required to cause the initial liquefaction increases with f, a unique tangent correlation function exists between the generalized shear strain amplitude gamma(ga) and the peak excess pore pressure ratio r(umax) (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 off. This indicates that liquefaction resistance of saturated coral sands increases with f.