【摘要】 地震反应分析中的输入界面是一种规定的假想基岩面,其选取具有很大的不确定性,对确定地震动参数的影响很大。本文以北京地区存在剪切波速较高的卵石硬夹层场地为研究对象,探讨实际工程场地中能否将硬夹层选作地震动输入界面的问题。利用一维等效线性化波动方法,对390个含有剪切波速高于500m/s的卵石层场地模型进行地震反应分析计算,讨论卵石层的上覆土层、下伏土层以及卵石层自身特性对地震反应分析结果的影响。计算结果显示,厚度5m左右、剪切波速小于600m/s的卵石层作为地震动输入界面是否合理,主要取决于上覆土层和下伏土层,而卵石层厚度和剪切波速的影响很小。对于一般性工程,当上覆土层厚度大于15m,下伏土层厚度在10m以内时,选取硬夹层顶面与选取钻探揭示的基岩或剪切波速不小于500m/s的土体顶面为输入界面,计算结果差别不大;当上覆土层厚度达到60m,下伏土层的变化对计算结果影响很小。研究表明,在钻探没有揭示出基岩或坚硬土体时,埋深大于60m的硬夹层可以选为地震动输入界面,这一结论对实际的地震安全性评价工作具有一定参考价值。更多还原

【Abstract】 Inputting interface in seismic-response calculation is a required imaginary bedrock surface.The choice of different seismic inputting interfaces has a great influence on the ground motion parameters.In this paper,we will use the cobble layer with high shear wave velocity in the Beijing area to discuss whether the hard layer can be used as inputting interface in practical engineering,1-D equivalent linear wave methodology is adopted for the seismic-response calculation on 390 engineering site soil profiles which includes some cobble layers with shear wave velocity more than 500m/s.The result shows that overlaying soil and underlying ground of cobble layer play an important role in choosing sort of cobble layer with around 5m thick and less than 600m/s as reasonable inputting interface;thickness of cobble layer and wave velocity,on the other hand,play minor roles.For general buildings,when the overlaying soil is more than 15m thick and the underlying ground is less than 10m thick,there is no significant difference in calculation results when choosing hard layers or bedrock as inputting interface.In addition,variation of underlying ground’s thickness has less effect on calculation when the thickness of overlaying soil reaches more than 60m.Therefore,hard soil layers buried in 60m or more in depth could be used as the inputting interface in the absence of information about bedrock.更多还原