The seismic response of a highly heterogeneous hydraulic fill dam was evaluated by studying the natural frequencies of the first and second modes of vibration and analyzing the crest accelerations of different two-dimensional or 2D sections of the dam when subjected to two different earthquake excitations. The existing methods for determination of the natural frequency of earthen embankment structures can only be used to analyze the structural response at small strain levels. However, during seismic events, the natural frequency of an earthen dam is significantly affected by the nonlinear material behavior exhibited by the geomaterials at high strain levels. Hence, a novel method was devised to evaluate the strain-dependent natural frequency for plane strain 2D dam sections, using a synthesized multi-sine base excitation. The degradation of first and second natural frequencies of transverse vibration for all the 2D sections followed a linear trend when plotted against the respective crest’s root mean square strain on a logarithmic scale. The slope of the degradation curve was found to depend on the constituent material properties prevalent in the individual sections. The observed variations in natural frequencies and crest accelerations of the 2D dam sections were also used to assess the suitability of using two-dimensional plane strain analyses for studying the response of a long earthen dam having variability in material properties. Results indicate that there is a considerable chance of erroneous estimation of the seismic response of such highly heterogeneous earthen dams that are conventionally analyzed using plane strain models. A 2D analysis was found to merely capture the seismic response of the individual sections of the dam as independent entities while ignoring the stiffening or weakening effect of the adjacent neighboring segments that may have different material properties.

通过研究第一和第二振动模式的固有频率，并分析经受两种不同地震激励的大坝不同二维或二维截面的波峰加速度，评估了高度非均质水坝的地震响应。确定土堤结构固有频率的现有方法只能用于分析小应变水平下的结构响应。但是，在地震事件中，土坝的固有频率受土工材料在高应变水平下表现出的非线性材料行为的显着影响。因此，设计了一种新颖的方法，使用合成的多正弦基础激励来评估平面应变二维坝段的应变相关固有频率。当以对数标度相对于各个波峰的均方根应变进行绘制时，所有2D截面的第一和第二横向振动固有频率的衰减遵循线性趋势。发现降解曲线的斜率取决于各个部分中普遍存在的组成材料性能。所观察到的2D坝截面的固有频率变化和波峰加速度也被用于评估使用二维平面应变分析来研究具有材料特性变化的长土坝响应的适用性。结果表明，用常规的平面应变模型对这种高度异质土坝进行地震反应的估计有很大的机会。