渤海海域粉质粘土阻尼比对反应谱影响的定量分析

Quantitative analysis of silty clay's damping ratio's effect on response spectra in the Bohai Sea

粉质粘土层在渤海海域分布广泛,渤海场地土层剖面中常常含有6层左右的粉质粘土层.目前国内对土层的阻尼比的不确定性对场地地震反应计算结果的影响的研究很少且局限于定性分析.基于敏感度分析的方法,本文提出了一种定量分析土层阻尼比对地表反应谱影响的方法并进行了数值实验.实验选取了渤海海域三个典型土层模型作为土层地震反应分析模型,通过控制影响土层地震反应计算结果的其他参量不变,赋予原阻尼比一系列的偏差,求出了地表反应谱及其相关参数的变化,进而得到了反应谱及其相关参数对阻尼比的敏感度.实验结果表明：（1）反应谱对粉质粘土阻尼比的敏感度一般小于0.4,在小震、中震、大震的地震动环境下,反应谱敏感度的高值区依次分布在0.04-0.2s、0.1-2.0s、0.2-3.0s之间,敏感度最大值依次为0.37、0.32、0.30;（2）特征周期和地震影响系数最大值对粉质粘土阻尼比的敏感度较小且一般后者的敏感度大于前者,数值实验中两者的敏感度最大值依次为0.13和0.21.

Silty clay layers are widely distributed in the Bohai sea and engineering sites in Bohai often contain about 6layers of silty clay.Current domestic researches on influences of soil damping ratio＇s uncertainties on site seismic response calculation results are rare and mostly are qualitative.Based on sensitivity analysis method,this paper proposed a method to quantitatively analyze the impact of silty clay＇s damping ratio＇s uncertainty on response spectra and carried out a numerical experiment.In the experiment,three typical soil models of Bohai Sea were selected to make seismic response analysis.By adding a series of deviations to the original damping ratio and maintaining other parameters unchanged,the changes of response spectra and their related parameters were calculated,and the sensitivity values of response spectra and related parameters on damping ratio were obtained subsequently.The following results are indicated in this research：（1）Sensitivity values of response spectra on silty clay＇s damping ratio are generally less than 0.4.In small, medium and large earthquakes,the high sensitivity zones range between 0.04~0.2s,0.1~2.0s,0.2~3.0srespectively and the largest values are 0.37,0.32,0.30 correspondingly.（2）Sensitivity values of characteristic period and maximum seismic influence coefficient on silty clay＇s damping ratio are smaller and generally the latter is larger than the former.In this experiment,their largest sensitivity values are 0.13 and 0.21 respectively.