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本文通过唐山地震时北京通县西集地区的两个典型的液化和非液化场地的动力分析,讨论了液化场地的地震动问题。在分析中用埃万模型表示土在循环荷载下的应力应变关系,并用显式差分方法求解。考虑到孔隙水压力的上升和动力反应之间的相互影响,本文提出用半波法计算非均匀循环荷载引起的孔隙水压力。分析结果与宏观现象符合得较好,因此,对于这两个场址地震效应的异常现象可以作出合理的解释。
In this paper, the dynamic analysis of two typical liquefaction sites and non-liquefaction sites in the Xiji area of Tong County, Beijing during the Tangshan earthquake is used to discuss the problem of ground motion in liquefaction sites. In the analysis, the Ewan model is used to express the stress-strain relationship of the soil under cyclic loading and solved with the explicit difference method. Considering the interaction between the rise of pore water pressure and the dynamic response, the half-wave method is used to calculate the pore water pressure caused by non-uniform cyclic loading. The analytical results are in good agreement with the macroscopic phenomena. Therefore, a reasonable explanation can be made for the anomalous phenomena of the seismic effects of these two sites.