Abstract

The dynamic shear modulus and damping ratio, as important parameters of soil dynamics, are indispensable for the evaluation of seismic safety and analysis of soil layer seismic response. Due to the limited existing research into marine soil’s dynamic shear modulus and damping ratio, there is a failure to get the reference values, along with the reference values for relevant parameters of soil. The soil physical mechanics and dynamic triaxial test research concerning the 25 samples of the Yellow Sea offshore project in Sheyang, Jiangsu Province were made in this paper, where the particle-grade curve of marine soils was also given. According to the current research theory, the method of determining the confining pressure values was explained in detail. Eventually, a linear influence on the maximum dynamic shear modulus with the increase of effective confining pressure was established, following research into the relationship between the maximum dynamic shear modulus and the effective confining pressure, using the hyperbolic model proposed by Hardin. According to the attenuation model relationship of G/G_max proposed by Martin, fitting with least square method, the relationship between the dynamic shear modulus and damping ratio of marine soils with shear strain was discussed. The results demonstrate that with the increase of the shear strain, the dynamic shear modulus ratio shows a trend of slight change followed by quick decrease and the damping ratio shows a trend of slow increase followed by quick increase. The reference values for dynamic shear modulus and damping ratios of various marine soils were proposed, via comparison with existing research results. The research results obtained provide basic data for marine soil dynamics and seismic engineering research.

摘要

动剪模量和阻尼比作为土体动力学的重要参数，对于地震安全性评价和土层地震反应分析是必不可少的。由于现有对海洋土壤动态剪切模量和阻尼比的研究有限，未能得到参考值，以及土壤相关参数的参考值。对江苏射阳黄海近海工程的25个样品进行了土壤物理力学和动力三轴试验研究，并给出了海洋土壤的颗粒级曲线。根据目前的研究理论，对围压值的确定方法进行了详细说明。最终，利用Hardin提出的双曲线模型研究了最大动态剪切模量与有效围压的关系，建立了随有效围压增加对最大动态剪切模量的线性影响。根据衰减模型关系Martin提出的G / G _max，采用最小二乘法拟合，讨论了海洋土壤的动剪切模量与阻尼比与剪切应变的关系。结果表明，随着剪应变的增大，动剪切模量比呈现出先小幅变化后快速下降的趋势，而阻尼比呈现出缓慢增加后快速增加的趋势。通过与现有研究结果的比较，提出了各种海洋土壤的动态剪切模量和阻尼比的参考值。所得研究成果为海洋土壤动力学和地震工程研究提供了基础数据。