考虑水平薄弱层的碾压混凝土拱坝振动台试验研究

由于碾压混凝土坝的施工工艺特点及特殊情况的出现,局部易形成薄弱层。为探究水平薄弱层的存在对拱坝地震超载能力与失效模式的影响,在振动台上进行了大坝模型动力破坏试验。模型的建立基于弹性力-重力准则,在相似关系设计时考虑了原型与模型材料力学特性的率敏感性,同时在动态加载条件下进行了含薄弱层的模型材料劈拉试验。选择模型基频对应的谐波逐级加载研究拱坝在超载作用下的反应。试验表明,拱端横缝的张开以及拱冠附近诱导缝的开裂释放了拱向约束,使得拱冠梁水平薄弱层处的梁向作用增强,易发生破坏。通过本次试验结果与不考虑薄弱层的研究结果对比,得出结论:水平薄弱层的存在并没有显著降低坝体整体超载能力,主要影响拱向约束减弱后,梁向位置进入悬臂梁加载模式后的失效模式。本文研究结果可为评估水平薄弱层的存在对拱坝超载能力与失效模式的影响提供试验依据。

Experimental study on impact of horizontal weak layer on dynamic failure mechanism of Roller Compacted Concrete Arch Dam

Due to the characteristics of Roller Compacted Concrete(RCC) dam construction technology as well as special circumstances,the dam is easy to form horizontal weak layers locally. In order to study the impact of horizontal weak layers on overload capability and failure mode of RCC arch dam,a dynamic rup-ture test was carried out on the shaking table. The establishment of the model was based on elasticity-gravi-ty similarity law. Meanwhile,the rate sensitivity of the mechanical properties of materials was taken into ac-count in designing the dam model. In order to provide the material properties information, several groups of splitting tensile test which containing a weak layer were carried out under dynamic loading. Sine waves corresponding to fundamental frequency loaded on the dam progressively to observe the responses of arch dam under overloading. The results show that structural joints are opened to release the arch constraints, which leads to the horizontal weak layer of crown cantilever prone to damage. Compare the results of this test results to previous study regardless of horizontal weak layer, it can be concluded that the presence of weak layer mainly affects the dam failure mode, but does not significantly reduce the overall overload ca-pacity of the dam structure. The result of this study is helpful to understand the effect of horizontal weak layers on the overload capacity and failure modes of RCC arch dams.