Experimental study on influences of fines content on dynamic deformation characteristics of saturated coral sand

In order to meet the urgent need for the cyclic characteristic parameters of coral sand in the proper engineering analysis of both military and civilian function facilities located in Nansha reefs and offshore marine areas, it is an important and emergent scientific task to study the dynamic deformation characteristics of the coral sand of the Nansha Islands in China. A series of resonance column tests are carried out on the saturated coral sand specimens from Nansha Islands. The aim of the tests is to investigate the effects of relative density D_r, initial effective confining pressure \sigma '_\textm and fines content F_C on the dynamic deformation characteristics of the specimens. The test results show that the stress exponent n, reflecting the rates of G_max increment due to the enhancement of \sigma '_\textm , presents a soil-specific constant. Synthesising the test data here and from three saturated sandy soils in the literatures, it is found that the stress-corrected maximum shear modulus G_max/( \sigma '_\textm / p_\texta )ⁿ decreases monotonically with the increase of the equivalent skeleton void ratio e, and a power relationship between G_max/( \sigma '_\textm / p_\texta )ⁿ and e_\textsk^\text* is then obtained. At the same strain level, the dynamic shear modulus G of the coral sand decreases with the increase of F_C, and increases with the increase of D_r and \sigma '_\textm . F_C, D_r and \sigma '_\textm have few effects on the damping ratio when the shear strain \gamma < 10^-4, but have a significant effect on the damping ratio when \gamma > 10^-4. D_r and \sigma '_\textm have no obvious influences on the dynamic shear modulus ratio G/G_max. When 0% ≤ F_C ≤ 30%, the G/G_max- \gamma attenuation curve continues to decline with the increase of F_C. The recommended values of fitting parametes A and B of the Davidenkov model for the coral sand are given, and it is found that the reference shear strain \gamma _0 decreases linearly with F_C.