小应变下舟山海相软土动剪切模量与阻尼比试验研究

Dynamic Shear Modulus and Damping Ratios of Zhoushan Marine Soils under Small Strains

以舟山海域海底原状海相软土为研究对象,利用GDS共振仪对各深度范围土样在不同围压下进行了一系列动力试验,得到了各深度范围土样在不同围压下动剪切模量和阻尼比随动剪切应变的变化趋势。试验结果表明：1×10-6-1×10-2应变范围内深度对舟山海相软土动剪切模量和阻尼比的影响不太明显;随着动剪应变的增加,动剪切模量逐渐衰减,阻尼比逐渐增大;围压对动剪切模量比G/Gmax和阻尼比D/Dmax的影响比较明显,围压越大G/Gmax越大,阻尼比D/Dmax越小。通过理论分析采用修正的Hardin-Drnevich模型给出其归一化动剪切模量比和阻尼比随剪应变变化关系曲线,并且给出了舟山海域海相软土G/Gmax和D的推荐值以及与规范值、袁晓铭推荐值加以比较。试验及分析结果加深了对舟山海域海相软土动力特性的认识,也进一步为海洋底盘工程建设提供了可靠的动力学参数。

This paper presents the research results of undisturbed marine soft soil samples from Zhoushan areas. The index properties of the marine soils from the sampling areas are reviewed. The dynamic properties of these marine soil samples retrieved from different depths are tested by the resonant column method under various confining pressures. The resultant shear modulus and damping ratios with relation to the various magnitudes of dynamic shear strains （1×10^-8 -1×10^-2） are obtained. The results indicate that, within the variation range of dynamic shear strains between 1×10^-6 and 1×10^-2, the sampling depth has minimal influence on the dynamic shear modulus and dynamic damping ratio; with the increase of dynamic shear strain, the dynamic shear modulus decreases and the damping ratio increases; the confining pressure has an obvious effect on both the ratio of dynamic shear modulus G/Gmax and the damping ratio D/Dmax, that is, the large the confining pressure is, the higher val ue of G/Gmax and the smaller of D/Dmax. The normalized dynamic shear modulus ratio and the damping ratio with related to the dynamic shear strain are obtained based on the theoretical analysis with the modified Hardin-Drevich model. These values are compared with the code recommended values as well as the values recommended by Yuan. These test results provide a better understanding of the dynamic properties of the Zhoushan marine soils.