软弱夹层土对软土场地地震效应的影响

Soft interayer on effects of earthquake response for soft site

本文以来自天津某工程的一场地为原型,对软夹层的埋深和厚度对软土场地地震效应的影响进行了数值分析。为了分析软弱夹层的埋深和厚度对地表地震动参数的影响,分别对原剖面进行了以下处理:软弱夹层的埋深从2 m增加到62 m,构造了16个剖面:软弱夹层的厚度从2 m增加到10 m,构造了5个剖面。选用Taft、El Centro和Northridge地震记录作为输入地震动,利用程序SHAKE91对不同的构造剖面、不同的输入地震波及不同的峰值加速度水平,进行了场地地震反应分析,结果表明:对于给定的输入地震动和峰值加速度水平,随着软弱夹层埋深的增加,地表加速度峰值和放大系数九都有减小的趋势,当埋深超过一定值后,地表加速度放大系数小于1．0:软弱夹层厚度对地表加速度峰值的影响与软弱夹层所处位置有关。

Based on the soft site from Tianjin, the depth and thickness of soft interlayer on the effect of earthquake ground motions of soft site is analysed. The effect of the depth and the thickness of soft interlayer is analyzed： the depth of soft interlayer is increased from 2 m to 62 m, and 16 site profiles are constituted, the. thickness of soft interlayer is increased from 2 m to 10 m, and 5 site profiles are constituted. In numerical analysis earthquake acceleration time-histories of Taft record, E1 Centro record and Northridge record are regarded as input ground motion, and their peak values of acceleration time-histories are adjusted as 0.35m/s^2. 0.70 m/ s^2 and 0.98 m/s^2. Through the numerical analysis of different cases by program SHAKE91, the following can be concluded： for given input ground motion and peak acceleration, when the depth of soft interlayer is increased, the peak values of ground motion acceleration response and their amplification factors will be lessening; when the depth o f soft interlayer exceeds a critical value, the amplification factors will be less than 1; the effect of thickness of soft interlayer on the earthquake response of deep soft sites is related to its depth,