辽东湾近海海底土小应变动力特性试验研究

Experimental study on the small-strain dynamic properties of offshore seabed soil in Liaodong Bay

开展场地地震动反应分析是众多海洋工程活动顺利实施和长期安全运行的重要保障,其中查明海底土小应变动力特性是十分关键的。文章借助海上原位钻孔取样和室内共振柱仪对辽东湾近海海底土小应变动力特性开展试验研究,探讨前人总结提出的滨海海底土初始动剪切模量G_(max)预测经验公式在辽东湾海域的适用性,对比文章试验结果与周边海域已有海底土剪切波速测试结果,分析小应变范围内海底土动剪切模量的衰减特征和阻尼比发展演变趋势,并同时进行定量化模拟预测,评价海底土动剪切模量衰减曲线的归一化特征。研究结果表明:(1)共振柱试验得到的原状海底土剪切波速与周边海域已有海底土剪切波速测试结果吻合良好;(2)相比起陆地土,海洋土在小应变范围内归一化动剪切模量G/G_(max)衰减得更慢,阻尼比增长得也更慢;(3)通过引入临界剪应变,不同土类和埋深对应的海底土小应变动剪切模量衰减曲线可以进行归一化。研究成果对合理开展海洋工程场地地震动反应分析评价具有一定的指导意义。

The seismic response analysis of site is an important guarantee for the smooth implementation and long-term safe operation of many offshore projects,and it is very important to study the small strain dynamic properties of seabed soil.In this paper,the small-strain dynamic properties of offshore seabed soil in the Liaodong Bay were tested and analyzed by using the in-situ borehole sampling and indoor resonant column instrument.The applicability of the existing empirical formula for predicting the initial shear modulus G_(max) of seabed soil was discussed.The test results in this study were compared with the existing shear wave velocity test results of seabed soil in the surrounding sea area.The attenuation characteristics of dynamic shear modulus and the development trend of damping ratio of the seabed soil in small strain range were analyzed,and a quantitative simulation was carried out to evaluate the normalization characteristics of dynamic shear modulus'attenuation curve of seabed soil.The results showed that the shear wave velocity of undisturbed seabed soil obtained by resonance column test is in good agreement with the existing test results in the surrounding sea area.Compared with land soil,the normalized G/G_(max) of marine soil decays more slowly and the damping ratio increases more slowly in the small strain range.By introducing the critical shear strain,the attenuation curves of small strain dynamic shear modulus of seabed soil corresponding to different soils and different buried depths can be normalized.These research findings can provide some guidance in reasonably evaluating the site response of offshore projects.