天津滨海软土场地的大震远场作用

Far-field strong earthquake effect in Tianjin coastal soft site

利用天津滨海地区丰富的地震地质钻孔资料及测试数据,建立了相应的地震反应模型.选取美国加州1992年Landers地震的远场记录P0841作为基底输入,采用工程上常用的等效线性化方法进行了土层地震反应分析,以期对天津滨海软土场地的大震远场作用得到一些定性的认识.结果显示,天津滨海软土场地对远场大震地震动峰值加速度的放大作用比较显著,但不同场地条件放大作用有明显差异,Ⅳ类场地的放大效应明显减弱.对基岩与地表反应谱比的分析显示,滨海场地对基岩地震动的不同频率分量的放大作用具有明显的不同,对短周期分量甚至出现了缩减,但当滨海软土场地受到与场地卓越周期相"吻合"的地震动影响时,可能会产生很可观的放大作用,这对建在其上的高层、超高层建筑可能会构成较大的威胁.

Using data from boreholes and related shear wave observations, and test results in Binhai sites, we found lots of correlative seismic analysis soil models. Selecting the far-filed ground motion record P0841 of 1992 Landers MwT. 3 earthquake in California as basement input, we applied the equivalent linearization method, which is wildly used in engineering to analyze the far-filed strong earthquake effect, to find some qualitative and instructive understanding on soil seismic response. The results show that the amplification effect of seis- mic peak ground acceleration （PGA） in Binhai soft site is significant, but there are some differences in different class site, e. g. , the effect on IV class site re- veals an obvious decrease. Moreover, the calculated response spectra ratio be- tween basement and ground shows that the amplification effect of different frequency component of basement input is so different at Binhai soft site that short period motion even exhibits decaying. There is, however, a considerable ampli-fication when the input seismic wave has principal period component coincide with the predominant period of the Binhai soft site. That would be a great risk for high-and super high-buildings constructed on soft site.