Experimental study on dynamic shear modulus and damping ratio of calcareous sands in the South China Sea

The dynamic shear modulus and damping ratio are two important parameters for the dynamic stability analysis of geotechnical structures and offshore sites. In order to evaluate the dynamic characteristics of calcareous sand in the offshore sites, the resonant column tests are performed on the calcareous sand by GCTS resonant column apparatus. Meanwhile, the effects of effective confining pressure and relative density on the dynamic shear modulus and damping ratio are investigated and compared with those of the quartz sand. It is found that the calcareous sand shows higher maximum dynamic shear modulus, higher damping ratio, and faster stiffness degradation than the quartz sand under similar states of effective confining pressure and relative density. Generally speaking, the calcareous sand shows higher G_max than the quartz sand when the shear strain is less than 0.1%. Finally, a mathematical model for the normalized dynamic shear modulus and damping ratio of the calcareous sand is established according to the test results in this study. Based on the existing researches on the calcareous sand, the variation ranges of the normalized dynamic shear modulus and damping ratio of the calcareous sand are given, and they may provide the basis for the dynamic stability analysis of buildings in the construction of calcareous sand sites.