Experimental study on the cyclic response of Nanhai Sea calcareous sand in China

Considering that the foundation soil (calcareous sand) of offshore platforms is subjected to wave loadings of different heights in a long time, cyclic triaxial tests are conducted on the Nanhai Sea calcareous sand under different loading conditions, i.e., amplitude, initial effective confining pressure, frequency, and waveform. Test results indicate that the failure of Nanhai Sea calcareous sand under cyclic loading is not only governed by the gradual development of excess pore water pressure but also by the accumulation of axial strain. There is a dilative tendency in loose or dense Nanhai Sea calcareous sand inhibiting the full liquefaction, which leads to the failure type of cyclic liquefaction. The effect of loading conditions on the excess pore water pressure, the axial strain, the secant modulus, and the cycle numbers to failure was investigated. The effect of loading amplitude, effective confining pressure, and waveform is profound, while the effect of frequency is not obvious. The cycle numbers to failure at different cyclic stress ratios demonstrated that the liquefaction resistance of Nanhai Sea calcareous sand is larger than that of calcareous sand in other sea areas.