Abstract: Studies on the effect of near-surface overburden soil layers on seismic motion have shown that the overburden soil layers have a significant impact on the seismic effect of the site due to the formation age, genetic type, thickness difference, structure, and dynamic characteristics of the soil layers. In this paper, the one-dimensional seismic response analysis of a nuclear power plant site containing a thick hard interlayer was conducted to discuss the influence of the hard interlayer thickness on the site seismic response, so as to provide a basis for determining the seismic motion parameters for seismic design of similar sites. Based on the engineering geological data of a nuclear power plant site, five models of one-dimensional soil-layer seismic response analysis were built, and the equivalent linear method of the one-dimensional site seismic response was applied to analyze the effect of the interlayer thickness on the peak acceleration and the acceleration response spectra of the site seismic response. The seismic response characteristics of the site and influence rules of the hard interlayer thickness are summarized as follows:1)Under different input seismic motion levels, the peak acceleration at the top of the hard interlayer was less than the input peak acceleration, and the peak acceleration at the ground surface of site was greater than the input peak acceleration. 2)Under the same input seismic motion, the ratios of the peak accelerations at the top of hard interlayer to the input peak accelerations were smaller than the ratios of the peak accelerations at the ground surface to the input peak acceleration, and these ratios first decreased and then increased gradually with the increase of the hard interlayer thickness; while for the same hard interlayer thickness, these ratios gradually decreased as the input peak acceleration increasing. 3)For the same input seismic motion, the ratios of the peak accelerations at the ground surface of site to those at the top of the hard interlayer increased gradually as the hard interlayer thickness increased; however, corresponding to different hard interlayer thicknesses, the variation characteristics of ratios which are the peak accelerations at the ground surface of site to those at the top of the hard interlayer were inconsistent with the increase of the input peak acceleration. 4)The hard interlayer had a significant influence on the short-period acceleration response spectrum and the thicker the hard interlayer was, the wider the influence frequency band would be; while for a special hard interlayer thickness, the influence frequency band is certain, and the hard interlayer had little effect on the acceleration response spectrum coordinates outside this frequency band, the longer the period is, the less the influence of the hard interlayer on the acceleration response spectrum coordinates. The seismic response characteristics of the site and influence rules of the hard interlayer thickness indicate that the hard interlayer thickness has a significant impact on the peak acceleration and the acceleration response spectra of the site seismic response, and the hard interlayer has obvious isolation effect at the seismic motion, and the increase of its thickness reduces the nonlinear effect of the site and leads to the wider influence frequency band. Meanwhile, the higher the input peak acceleration is, the stronger the nonlinear effect of the site, and it's remarkable that the soft layer overlying the hard interlayer has a significant amplification effect on the seismic motion.

Key words: site condition, earthquake damage, equivalent linearization, earthquake response, nonlinear

摘要： 文中基于某核电站场地工程地质资料，构建了5个硬夹层厚度不同的工程地质剖面。在此基础上，建立了5个一维分析模型，并应用一维土层地震反应等效线性化方法分析了硬夹层厚度对场地地震反应加速度峰值与反应谱的影响。分析结果表明：硬夹层的厚度对场地地震反应峰值加速度与反应谱有较明显的影响，硬夹层厚度的增加减小了场地的非线性效应；不同输入地震动水平下，硬夹层顶板的峰值加速度均小于输入加速度峰值，地表峰值加速度均大于输入加速度峰值；相同输入地震动水平下，随着硬夹层厚度的增加，硬夹层顶板和场地地表峰值加速度与输入峰值加速度之比均表现为先逐渐减小后逐渐增加的趋势，而场地地表与硬夹层顶板的峰值加速度之比随硬夹层厚度的增加总体逐渐增加；硬夹层厚度相同时，随着输入峰值加速度的增大，硬夹层顶板和场地地表的峰值加速度与输入峰值加速度之比逐渐减小；硬夹层仅对一定频带内的加速度反应谱有影响，其厚度越大，影响频带越宽，而对于影响频带之外的加速度反应谱影响很小，同时周期越长影响越小。

关键词: 场地条件, 地震灾害, 等效线性化, 地震反应, 非线性