Triaxial Test on Dynamic Characteristics of Unsaturated Calcareous Sand in South China Sea

To solve the problem of dynamic characteristics of unsaturated calcareous sand in the South China Sea, calcareous sand was selected to carry out dynamic triaxial test and effects of different parameters on the mechanical properties were studied systematically in this paper. Results show that the development law of dynamic strain and dynamic pore pressure of unsaturated calcareous sand is obviously different from that of saturated calcareous sand. Under the saturated state, the dynamic pore pressure developed slowly and kept near-linearly increasing in the early stage of the test, and the dynamic pore pressure fluctuations was large in the middle and late stage of the test. By contrast, the development law of calcareous sand in an unsaturated state was opposite. The dynamic strain curve of unsaturated calcareous sand had obvious instability point only under the low confining pressure. There was no obvious instability point under the effective confining pressure of 100 kPa and 150 kPa, and there was obvious instability point under each effective confining pressure in the saturated state. The development trend of dynamic pore pressure under the unsaturated state was greatly affected by the matric suction, and with the increase of the matric suction, the maximum dynamic pore pressure showed an overall decreasing trend. The maximum dynamic pore pressure under the high matric suction was smaller than that under the low matric suction.