【作者】 周宁娜；

【导师】 李宗利；

【作者基本信息】 西北农林科技大学 ， 水利水电工程， 2009， 硕士

【摘要】 高拱坝的开裂分析和安全评价是拱坝设计中需要考虑的一个重要问题。本文应用有限元法从网格密度、材料本构模型定量分析和坝体体型定性分析两个角度对高拱坝坝体开裂分析关键问题进行了初步探讨,建立了高拱坝在考虑开裂作用下的非线性数值分析模型,重点研究了不同位置、不同深度的裂缝对高拱坝的静、动力特性的影响。本文主要开展了以下工作:(1)选择典型工程实例,分别建立不同坝体体型、不同网格密度和不同本构关系的三维高拱坝数值分析模型,应用非线性有限元分析基本理论,研究了坝体体型、网格疏密及本构模型的不同对高拱坝开裂分析结果的影响。研究表明,拱坝自身的体型以及坝址区的河谷形状是影响拱坝开裂的一个重要的因素;网格的疏密对拱坝高应力区、角缘应力集中部位应力影响较大,在这些部位适当加密网格可以获得拱坝较为真实的应力状态;对于坝高较大,应力水平较高的高坝,其材料的非线性性态十分显著,采用弹塑性开裂模型进行开裂分析更能反映坝体的实际应力状况。(2)应用弹塑性理论,在坝体不同位置和不同深度人工设置裂缝,研究裂缝深度以及裂缝面上有无水压对高拱坝静动力特性的影响。结果表明,裂缝的存在降低了结构的刚度,造成空库和正常蓄水位时坝体自振频率随裂缝的深度加大而下降。裂缝对坝体的影响主要体现在裂缝附近的局部区域,裂缝的存在使得坝体高应力区拉应力得到显著释放,引起应力重分布,裂缝深度的增加对拱坝的整体性未产生显著影响。同时,初始裂缝存在时,裂缝面有无水压作用对坝体的位移和应力响应影响较大,裂缝面上的水压力是促使裂缝进一步扩展的主要因素。更多还原

【Abstract】 Cracking analysis and safety evaluation of high arch dam are very important problems to consider in the designation of arch dam. This paper carries a preliminary study on key problems of high arch dam’s cracking from mesh grid density, material constitutive model and dam figure by using finite element method. The nonlinear numerical analysis model of high arch dam with cracks is established, and effects on static and dynamic characteristics of high arch dam is mainly studied under different crack location and crack depth. The main tasks of this paper are as following:First, this paper chooses typical engineering cases and establishes 3D high arch dam models for numerical analysis in different dam figure, mesh grid density and material constitutive, then the effect on the cracking results of high arch dam under different dam figure, crack location and crack depth is analyzed on the basis of the nonlinear finite element method elementary theory. The results indicate that dam figure and canyon shape at dam site area are very important factors which affect the cracking of the arch dam. Mesh grid density has significant effects on the stress field at high stress area and stress concentrated zone of the arch dam, and mesh grid of these areas should be refined to obtain more reliable stress state. Elastic-plastic cracking model should be used to analyze the cracking of high arch dam which has greater height and stress level.Second, cracks are set manually at different location with different depth on dam body, and effects on static and dynamic characteristics of high arch dam is studied under different crack depth and water pressure in fracture by using elastic-plastic theory. The results show that cracks reduces stiffness of the structure, and make the self-oscillation characteristic of the dam body decrease whether the reservoir is empty or full. The tensile stress of the high stress zone is released obviously and stress redistribution is caused by cracks. Effects on dam properties due to cracking mainly embody local zone near the cracks. Increment of crack’s depth has little effects on the entire characteristics of the arch dam. Meanwhile, water pressure in fracture has great influence on displacement and stress of the dam. And it is the important factor to cause the further propagation of the cracks.更多还原