Abstract: A series of resonant column tests was conducted on coral sands from the Nansha and Xisha Islands of the South China Sea with different grain gradations. It is found that there are upper and lower limits in the small-strain shear modulus, G0 distribution ranges of coral sand from different seas and with different gradations under the same effective confining pressure . The maximum and the minimum void ratios, emax and emin, are comprehensive state parameters for effectively characterizing the particle gradation and shape characteristics of sandy soils. The limit values of G0 are consistent with the extrapolated G0 results at emax and emin. Under the same , the lower limit values of G0 (G0min) and the upper limit values of G0 (G0max) of coral sand decrease with the increasing emax and emin, respectively. Empirical formulas for predicting the G0 limit values of coral sand are established based on the relationship between G0min and emax, and the relationship between G0max and emin under different . The G0 of coral sand with various void ratios e can be determined by nonlinear interpolation using the values of G0min, G0max and the relative density Dr. The new G0 prediction model has good universality for sands with similar morphology and mineralogy of the particle forms and different gradations. For other types of sandy soils, a correction coefficient a is introduced to consider the effect of the mineral composition on G0. The general applicability of the new G0 prediction model, superior to the common Hardin prediction model, is validated by the G0 experimental data published in the literatures.

Key words: small-strain shear modulus, the maximum and the minimum void ratios, perdition model, coral sand