Abstract: Previous studies on the dynamic characteristics of calcareous sand mostly focused on the saturated calcareous sand, and sine waves were often applied to replace seismic loads in the test process. In order to overcome this defect, a dynamic triaxial seismic load input method is proposed to convert the acceleration time history of seismic load into stress time history. Dynamic triaxial test on calcareous sand in the South China Sea is conducted to study the dynamic characteristics of unsaturated calcareous sand in single and multiple seismic load durations. The test results show that the strain and pore water pressure of calcareous sand develop in a stepwise manner under the seismic load, and the failure strain has both positive and negative values, that is, the failure type has both tensile failure and compression failure, which is different from the development laws of dynamic pore water pressure and dynamic strain under sinusoidal load; with the increase of matrix suction, the maximum dynamic pore pressure shows an decreasing trend, but the maximum pore pressure of calcareous sand samples does not reach the effective confining pressure.

Key words: seismic load, calcareous sand, unsaturated, dynamic triaxial test, dynamic characteristics