Reliability Assessment of the San Fernando Dam During the Northridge Earthquake

9416469莱西在加利福尼亚州北岭地震期间，下圣费尔南多大坝的上游面横向向上扩展了几英尺。出现表面裂纹和砂粒沸腾。北岭地震期间的行为记录提供了一个机会来验证现有的最先进的方法来分析土坝的地震稳定性，包括液化和永久位移的预测。北岭地震期间在下圣费尔南多大坝收集的数据将用于评估大坝在地震发生期间和之后的可靠性。这将通过生成一系列可能的地面运动和土壤特性的实现，并使用通用的两阶段非线性有限元程序来确定性地分析每个可能的实现来实现。根据附近基岩场地的测量得到的频谱内容，模拟了坝基的地面运动。与液化发生和强度有关的材料特性被视为具有均值、方差的空间变化随机场，并且在可能的情况下，根据现场的实际测量得出空间相关结构。这些问题中的饱和土体被视为土体骨架和孔隙流体的两相连续体。孔隙水和土壤骨架行为是完全耦合的，从而解释了土壤变形时两种介质之间的相互作用。土骨架的非线性弹塑性行为用多屈服面塑性来模拟。对于每个分析，都会产生土体响应的时程，包括加速度、位移和孔隙水压力。得到的土体响应序列被统计处理，以产生对土坝系统可靠性的估计。***

9416469 Lacy During the Northridge, CA earthquake, the upstream face of the Lower San Fernando dam spread laterally upstream several feet. Surface cracks and sand boils developed. The documentation of the behavior is during of this during the Northridge earthquake provides an opportunity to validate an existing state-of-the-art method to analyze the seismic stability of earth dams, including the prediction of liquefaction and permanent displacements. Data collected at the Lower San Fernando dam during the Northridge earthquake will be used to assess the reliability of the dam during and after an earthquake event. This will be achieved by generating a sequence of possible realizations of the ground motions and soil properties and analyzing each deterministically using a general two-phase nonlinear finite element procedure. The ground motion at the base of the dam is simulated according to a spectral content derived from measurements at nearby bedrock sites. The material properties pertinent to the occurrence of liquefaction and strength are treated as spatially varying random fields with mean, variance and, where possible, spatial correlation structure derived from actual measurements at the site. The saturated soil in these problems is treated as a two phase continuum of soil skeleton and pore fluid. the porewater and soil skeleton behavior are fully coupled, thereby accounting for the interaction between the two media as the soil deforms. The nonlinear elasto-plastic behavior of the soil skeleton is modeled by multi-yield surface plasticity. for each analysis, time histories of soil response are produced, including accelerations, displacements and pore water pressures. The resulting sequence of soil responses is processed statistically to yield estimates of reliability of the earth dam system. ***