液化土层地震动模拟计算方法及验证

Method of simulating seismic ground motion in liquefiable soil layer

针对目前土层反应分析方法难以模拟液化土层地震动时程的缺欠,在工程力学研究所原有有效应力分析程序基础上提出了一个改进的计算方法并进行了验证。改进方法中,通过每个应力循环模拟土的非线性进程以及液化导致的土刚度衰减过程,并引入了新建立的适于非均等固结随机地震荷载作用下的孔压增长模型。将计算方法与实际地震记录及大型振动台实验结果进行了对比,结果表明:在峰值加速度、液化后波形变化、时频曲线及加速度反应谱等主要特征上,计算结果均与现场实际记录及振动台实验基本一致;在液化引起地震动特征变化上,计算出的液化较非液化土层加速度反应谱的增量与实验结果一致。说明所提出的改进方法可以用于液化土层地震动的模拟。

To simulate the seismic ground motion history in liquefiable soil layers,a revised effective stress method is proposed and verified. In the revised method,the non-linear behavior of soils and the process of rigidity attenuation due to liquefaction are considered by iteration in every stress cycle. The model which can calculate the water pressure of saturated sands under anisotropic consolidation is used in the calculation procedure. The method and procedure presented here are tested by comparing with the post-earthquake records and shaking table tests. The comparative results show that the calculated results are agreeable with the actual records and the shaking table tests on main features,such as the PGA,the changes of the acceleration histories during the liquefaction process,the time-frequency history and response spectra. Especially,the calculated results quite correspond to those of the shaking table tests for the liquefaction-induced increment of the acceleration response spectra. As a result,the revised method presented in this paper is practical to simulate the seismic ground motion in the liquefiable soil layers.