【摘要】 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。更多还原

【Abstract】 Dynamic simple shear tests on different types of sand under multidirectional earthquake loading are simulated by means of the finite element method.The reduced order bounding surface model is employed and its parameters are determined based on the results obtained from laboratory dynamic simple shear tests.148 groups of ground motions with multi-components from far and/or near fields of moderate and/or strong earthquake events at different site conditions are used as input motions for strain controlled and stress controlled dynamic simple shear tests.Effect of multidirectional earthquake loading on seismic compression of sand for different earthquake magnitudes site-to-source distances and properties of sand is studied.The results show that the ratio of vertical strain induced by multi-components of seismic loading and that induced by one component of seismic loading are greatly associated with earthquake magnitude,site-to-source distance and properties of sand,the ratio of vertical strain increases with the increasing earthquake magnitude and relative density of sand,and decreases with the increasing site-to-source distances.Great limitation exists in the method considering the effect of multidirectional earthquake loading on seismic compression proposed by Pyke et al(1975) due to its lack of considering the effect of characteristics of seismic loading and properties of sand.Also,the ratios obtained from stress controlled and strain controlled simple shear tests are greatly different and the mean ratios from the former are larger than those from the latter.更多还原