高拱坝开裂危险性分析

Cracking Risk Analysis of High Arch Dams

根据国内外各类混凝土试件的试验结果,总结归纳了各类不同受力状态下,混凝土真实强度的差异,并据此提出了一套简单实用的高拱坝开裂危险性分析方法。该方法可直接利用线弹性有限元或拱梁分载法等多种数值方法的三向应力计算结果,结合应力比和大坝混凝土强度,通过查图算法,直接求解拱坝结构任意一点的点安全度,从而预测拱坝相应部位的开裂危险性。二滩拱坝下游裂缝的算例表明,当考虑大坝混凝土三轴效应后,拱坝-坝肩整体点安全度要小于基于单轴强度模型的大坝点安全度,拱坝下游拉压应力组合导致区域结构强度降低是混凝土产生裂缝的内因,在温度荷载、地质条件等外部因素的联合作用下,最终导致了拱坝的开裂。

According to the test results of various concrete specimens conducted in China and abroad, the concrete real strangths under diffent external loads are summarized, and a sinple practical cracking risk analysis method of high arch dams is presented. In this method the results of the dam triarial stresses calculated by use of the numerical analysis methods, such as finite element method or trial -load method, can be directly used, the dam concrete strength, stress distribution and stress ratio are considered, though refering to the chart algorithm, the real safety degree of any point in the arch dam can be obtained. Thus the cracking danger of the arch dam is predicted. As an example, the cracking analysis in the downstream part of Ertan arch dam is conducted. The analysis results show that the arch dam concrete strength reduction due to the multiaxial effect is the internal cause of the concrete cracking and under the combined effects of the external factors, such as the temperature load, geologic conditions and so on the arch dam cracking hapens. Considering the multiaxial effect of the concrete, the real safety degree of the arch dam - abutment system is lower than that of the arch dam considering umiaxial strength.