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利用有限元数值方法模拟不同类型砂土在多向地震荷载输入条件下的动单剪试验,采用弹塑性边界面模型,通过室内动单剪试验实测结果确定模型参数,计算分析地震动特性对砂土震陷的影响。研究结果表明:地震波加载次序、不对称性、加载方向、地震波类型、加载维数对砂土变形影响显著。当大的应力脉冲出现时,砂土竖向应变明显增大,其增量的大小受到大波出现的时刻和次序影响明显;在其他条件相同时,地震波不对称性越明显,砂土竖向应变越大;反向加载对砂土具有向下压应力作用,提高竖向应变值,正向加载效应则与此相反;现有的一些规范方法取20周作为转换后的等幅应力波的标准作用次数进行震陷定量计算,其对于振动型和冲击型地震波输入等效性结果差别较大;Tokimatsu和Seed(1987)震陷分析方法按2倍单向水平地震动引起的砂土震陷简化确定多向地震动引起的砂土震陷,其结果尚待商榷。
The single-shear test of different types of sand under multi-directional seismic load input was simulated by finite element method. The elasto-plastic boundary surface model was used to determine the model parameters through indoor single shear test. The characteristics of ground motion Impact of Earthquake. The results show that: seismic wave loading order, asymmetry, loading direction, seismic wave type, loading dimension have a significant impact on the deformation of sand. When a large stress pulse appears, the vertical strain of sand increases obviously, and the increment of sandstone is obviously influenced by the moment and order of big wave. When the other conditions are the same, the seismic wave asymmetry is more obvious, the vertical strain of sand The reverse loading has the effect of downward compressive stress on the sand and the vertical strain value is increased, while the positive loading effect is the opposite; the existing standard methods take 20 weeks as the standard of the converted constant amplitude stress wave The quantitative calculation of the amount of seismic subsidence has an obvious effect on the input equivalence of the vibrational and impulsive seismic waves. The seismic collapse analysis method by Tokimatsu and Seed (1987) Determine the earthquake caused by multi-directional sandstorm collapse, the results remain to be discussed.