高拱坝振动台地震破坏试验研究及数值仿真

EXPERIMENTAL STUDY AND NUMERICAL SIMULATION FOR SEISMIC FAILURE OF HIGH ARCH DAM ON SHAKING TABLE

以大岗山拱坝模型的动力破坏试验为基础,从试验和数值计算角度,对整体拱坝动力特性、薄弱部位、破坏形态以及抗震性能进行研究。采用和混凝土性能相似的脆性模型材料,通过逐级加载的方式在振动台上对整体拱坝进行从弹性到破坏整个过程的模型试验,分析坝体动态特性、加速度和应变的变化规律。并采用弹脆性损伤模型对混凝土拱坝在地震作用下损伤破坏的全过程进行数值仿真,探讨拱坝动力破坏过程、破坏形态,并与试验结果进行对比分析。结果表明:模型试验和对原型进行的数值模拟所得到的破坏过程和破坏形态都较为接近。在顺河向地震作用下,顶拱的坝中部位为地震应力最高的区域,是坝体薄弱的部位,整体拱坝首先在该位置出现裂纹,其次是顶拱距左右两岸1/4拱圈处。在强震作用下,拱向和梁向裂缝贯穿上下游,将导致拱顶中部的混凝土脱离坝体,丧失壅水功能。试验和计算结果相互印证,可呈现高拱坝在强烈地震作用下的损伤破坏过程及破坏形态,确定抗震薄弱环节,为混凝土高坝的抗震功能设计提供基础。

The seismic safety of a high arch dam is studied through shaking table test and numerical simulation. The dynamic characteristics of the high arch dam system, weak portions, failure mode, as well as aseismic behaviors during earthquakes are discussed. A type of brittle material which has the same characteristic as the common concrete is used to study the dynamic failure process of high arch dam adopting the step loading method on shaking table. The dynamic characteristics, the change law of dam acceleration and dynamic strain are investigated. An elasto-brittle damage constitutive model is applied to simulate and analyze the dynamic failure process of high arch dam under meizoseismic motion. The comparison between the calculated results and those obtained from shaking table tests shows that they are close and definitely verified each other. The study also shows that the top of arch crown and one-quarter point of both sides are the vulnerable parts of arch dam and cracks normally appear near these parts under meizoseismic motion along stream direction. The cracks along the stream direction cut across arch dam and concrete block falls down from the top of arch crown. The arch dam is endangered to the impounding function and the structure beating capacity. Vulnerable parts of the dam to earthquake loading and various factors that affect the earthquake-resistant behavior of the dam, such as the openings existing in the dam body, are discussed under meizoseismic motions of different levels. These researches provide basic data for performance-based aseismic design of high concrete arch darn.