南沙珊瑚砂的动剪切模量和阻尼比特性试验研究

珊瑚砂的物理力学性质与陆相沉积物有显著的差异。对南沙岛礁饱和珊瑚砂进行了不排水应变控制分级循环加载动三轴试验，研究了有效围压 和相对密实度Dr对饱和珊瑚砂动剪切模量和阻尼比特性的影响。通过与陆源砂砾土试验结果的对比发现：珊瑚砂与陆源砂砾土在最大动剪切模量Gmax、动剪切模量比G/Gmax曲线及其上下界、参考剪应变 、阻尼比? 曲线及其上下界等均存在显著的差异；珊瑚砂的Gmax比陆源砂的大，采用陆源砂Gmax的经验模型，珊瑚砂的Gmax将被低估约30%；珊瑚砂的非线性稍弱于陆源砂砾土，陆源砂砾土G/Gmax和? 的经验公式不适用于珊瑚砂。给出了珊瑚砂G/Gmax和? 的经验公式及相关参数。

Experimental study of dynamic shear modulus and damping ratio characteristics of coral sand from Nansha Islands

The physical and engineering mechanical behaviors between coral sand and terrigenous sandy soils are considerably different. To study these behaviours, a series of undrained multistage strain-controlled cyclic triaxial tests was conducted on saturated coral sand from Nansha Islands, South China Sea. The influence of effective confining pressure and relative density Dr on the dynamic shear modulus and damping ratio of coral sand was studied. Compared with the test results of coral sand and terrigenous sandy soil and gravel, significant differences were found in the maximum shear modulus Gmax, the shapes and the upper and lower boundaries of shear modulus ratio G/Gmax curves, reference shear strains , the shapes and the upper and lower boundaries of damping ratio ? curves. The maximum shear modulus Gmax of coral sand is higher than that of terrigenous sandy soil and gravel, and the Gmax of coral sand predicted by empirical equations of terrigenous sandy soil is underestimated by 30%. The nonlinearity of coral sand is slightly weaker than that of terrigenous sandy soil and gravel. The empirical formulas for predicting G/Gmax and ? of terrigenous sandy soil and gravel are not applicable for Nansha coral sand. The empirical formulas for predicting G/Gmax and ? of coral sand are proposed.