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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,选取包括大震、中震、近场、远场以及不同土质条件的148组具有完整记录的多向地震荷载时程对不同类型砂土试样进行单向和多向加载,分别进行应力和应变控制式动单剪试验,计算分析震级、震中距以及砂土特性不同的条件下多向地震荷载对砂土震陷问题的影响。结果表明:多向地震荷载对砂土震陷的影响具有较大的不确定性,多向和单向水平地震荷载引起的砂土竖向应变比与震级、震中距和砂土特性密切相关,震级越大,竖向应变比越大;震中距越大,竖向应变比越小;砂土相对密度越大,竖向应变比越大。另外,在应力控制和应变控制荷载试验条件下,多向和单向水平地震荷载引起的砂土竖向应变比差异较大,前者比值大于后者。
The single-shear test of different types of sand under multi-directional seismic load input was simulated by finite element method. The elastic-plastic boundary model was used to determine the parameters of the model by single-shear test in laboratory. , 148 near-field, far-field and multi-directional seismic load histories with different records of different soil conditions were used to unidirectionally and multi-directionally load different types of sand samples. Stress and strain controlled single shear tests were carried out respectively. The effects of multi-directional seismic loads on sand-subsidence are analyzed and calculated under different conditions of earthquake magnitude, epicenter distance and sand characteristics. The results show that the influence of multi-directional seismic load on sand subsidence is uncertain. The vertical strain ratio of sand caused by multi-directional and unidirectional horizontal seismic loads is closely related to the magnitude, epicentral distance and sand characteristics. The greater the magnitude, the greater the vertical strain ratio; the greater the epicentral distance, the smaller the vertical strain ratio; the greater the relative density of sand, the greater the vertical strain ratio. In addition, under the stress control and strain control load test conditions, the ratio of vertical soil strain caused by multi-directional and unidirectional horizontal seismic loads has a greater difference, the former ratio is greater than the latter.