Hydrodynamic Isolation of Concrete Dams

本课题为国家科学基金（NSF） 87-90“新颖性研究加急奖励”资助项目。研究了混凝土坝的水动力隔震保护方法。大坝不是与地面运动隔离，而是与动态水压力隔离，方法是在水库中锚定充气气球，在上游面上附加闭孔泡沫材料，或不断向水库注入气泡。这样，就消除了水库满水或接近满水时大坝响应可能出现的显著增加。将对这三个方案的潜在效益和成本进行评估。研究表明，强烈的地震代表着水库满或接近满的大型混凝土大坝的严重负荷，造成大面积开裂，后果不明。将混凝土坝与水动力效应隔离可以避免动力响应的增加。当水位从大坝高度的四分之三上升到顶峰时，这种增加变得非常显著。这项研究有可能影响现有地震缺陷大坝的改造和新大坝的设计。

This is a project supported under the "Expedited Awards for Novel Research" (NSF 87-90). The method of hydrodynamic isolation to protect concrete dams against earthquakes is studied. A dam is isolated, not from the ground motions, but from the dynamic water pressure by means of either anchoring gas-filled balloons in the reservoir, attaching a closed-cell foam material to the upstream face, or continuously injecting bubbles into the reservoir. Thus, the significant increase in response of the dam which may occur when the reservoir is full or nearly full is eliminated. All three schemes will be evaluated for potential benefit as well as cost. It has been shown that a strong earthquake represents a severe loading of a large concrete dam with full or nearly full reservoir, causing extensive cracking with unknown consequences. Isolating a concrete dam from hydrodynamic effects avoids the increase in dynamic response. This increase becomes significant as the water level is raised from about the three-quarter height of the dam to the crest. The study has potential to impact retrofit of existing dams with seismic deficiencies and the design of new dams.