重力坝-库水-地基相互作用分析方法比较研究

Comparative study of analytical methods of gravity dams-reservoir-foundation interaction

对5种不同高度的重力坝分别采用流固耦合模型与附加质量模型进行了坝体-库水系统相互作用的时域地震动分析.将这两种模型计算所得动水压力结果与Westergaard公式解析解相比较可知,约70m高的中低重力坝采用Westergaard公式计算动水压力就能满足工程实际的要求;对于160m以上的中高重力坝,采用流固耦合模型计算库水作用及坝体动力响应较为接近现实情况.从坝体频率、位移、峰值加速度(PGA)三个方面的结果可以看出,附加质量模型模拟地震条件下库水对坝体作用较流固耦合模型有一定的夸大,对中高坝而言更为显著.地基对200m级高坝库水作用的影响非常明显,在计算坝体与库水相互作用时地基作用不可忽略;对于70m高的中低坝,地基作用可以不用考虑.

Earthquake analyses of gravity dams with five different heights in time domains are performed on the fluid-structure coupling model and the added mass model respectively. The hydrodynamic pressures obtained from the two models are compared with Westergaard solutions, and the comparative results show that the accurate results of hydrodynamic pressure can be obtained by Westergaard formula for middle and low dams with the height of about 70 m, but reasonable results of the dynamic responses of dam-reservoir system should be obtained by the fluid-structure coupling model for high dams with the height of above 160 m. Based on the comparison between the results from fluid-structure coupling model and the added mass model for dynamic responses of dam-reservoir system, it is found that the results of the added mass model are larger than those of fluid-structure coupling model in the views of fundamental frequencies, displacements and peak ground acceleration （PGA） of dams. As for the dams with a height of about 200 m, the influence of foundation on dam- reservoir interaction is significant and must be considered. As for the dams with a height of about 70 m, the influence of foundation can be neglected.