高拱坝抗震安全评价指标研究——以白鹤滩拱坝为例

Study on seismic safety evaluation index of the high arch dam: A case study of Baihetan Arch Dam

为研究拱冠梁中上部在地震作用下的局部稳定性,提出合理的局部抗震安全评价指标,本文以白鹤滩拱坝为例,建立三维有限元模型进行数值模拟计算。将拱冠梁中上部作为研究对象,以基于坝段的抗滑安全系数及抗滑安全系数持时作为局部安全评价指标,研究了两个指标随地震动峰值加速度(PGA)的变化规律及其沿坝段高程的分布规律,并基于指标的统计结果明确了拱冠梁中上部薄弱位置。结果表明,随着PGA的增加,拱冠梁中上部抗震安全薄弱面所在的位置是逐步降低的。PGA低于0.8g时,拱冠梁中上部位抗震安全的薄弱面位于0.79~0.83倍坝高位置;PGA大于等于0.8g时,拱冠梁中上部抗震安全的薄弱面位于0.76~0.79倍坝高位置。本文计算结果与高拱坝振动台地震破坏试验结果相近,提出的评价指标应用于拱冠梁中上部的评价效果较好,可为高拱坝中上部抗震薄弱部位的定位及大坝安全监测提供参考。

In order to study the local stability of the middle and upper part of the crown cantilever under earthquake and put forward reasonable local seismic safety evaluation indexes, this paper takes Baihetan Arch Dam as an example to establish a three-dimensional finite element model for numerical simulation calculation.Taking the middle and upper part of the crown cantilever as the research object, and taking the anti-sliding safety factor and anti-sliding safety factor duration based on the monolith as the local safety evaluation indexes, the variation regulars with the peak ground acceleration(PGA) and distribution regulars along dam elevation of the two indexes are studied.Based on the statistical results of the proposed indexes, the weak position in the middle and upper part of the crown cantilever is determined.The results show that with the increase of PGA,the height of weak position in the crown cantilever decreases gradually.When PGA is less than 0.8g and greater than or equal to 0.8g,the weak surface of the middle and upper part of the crown cantilever is 0.79-0.83 times of dam height and 0.76-0.79 times of dam height, respectively.The results obtained in this paper are similar to the shaking table test results of high arch dams, and the evaluation effect of the proposed indexes is good when applied to the middle and upper part of the crown cantilever, which can provide reference for locating the weak position of high arch dam and dam safety monitoring under earthquake.