【作者】 周晖；

【导师】 李俊杰；

【作者基本信息】 大连理工大学 ， 防灾减灾工程及防护工程， 2010， 博士

【摘要】 地震作为一种严重的自然灾害,一旦发生强震便会给人们的生命财产带来巨大的损失。面板堆石坝作为一种常见的坝型,在导致其垮坝的各种要素中,失稳是最普遍的现象,目前我国的面板堆石坝建设方兴未艾,所以面板堆石坝的抗震稳定成为工程安全的关键,高坝大库的潜在风险使得高面板堆石坝抗震安全研究的意义重大而迫切。规范中规定的拟静力法在面板堆石坝动力稳定分析中的得到广泛的应用,加速度分布系数是拟静力法中的关键数据。但由于规范制定时间较早,且其中的数据主要来自二维分析,不能反应现代高面板堆石坝地震反应的特点以及河谷形状、地震动特性等对坝体动力反应的影响。随着计算机水平的发展,大规模面板堆石坝三维有限元动力稳定分析已经成为可能。采用三维有限元分析对高面板堆石坝的地震反应特性进行研究,特别是对坝体加速度分布进行研究,从而为面板堆石坝的抗震稳定分析提供依据,具有理论和实际应用价值。采用等价线性粘弹性模型对三维面板堆石坝进行了大量计算,并进行统计分析等研究工作。对面板堆石坝抗震稳定分析方法进行了比较研究。认为剪切梁法和集中质量法只能应用在有限的边界条件,无法准确模拟不同土质的坝体和坝基情况,也无法考虑水平截面上动剪应力的不同分布,特别是堆石体材料具有较明显的动力非线性性质,仅依靠线弹性模型或粘弹性模型是远远不够的。有限元法具有可用于非均质非线性问题,可适应复杂边界条件,既可以用于静力计算也可以用于动力计算等优点,高面板堆石坝的地震反应分析采用有限元数值解法,能够给出相对准确的解。采用非线性有限元法和等价线性化模型进行动力分析,对混凝土面板堆石坝坝高、河谷岸坡坡比、河谷宽度等对坝体加速度分布的影响进行了研究,特别是针对面板堆石坝坝高变化时引起的中心断面边坡点顺河向加速度分布规律进行了系统分析。得到一些有益的结论：加速度分布规律表现为在0～5／6H段加速度放大倍数较小,超过5／6H后,加速度放大倍数显著增加；河谷宽阔且河岸陡峭时,坝高对坝顶顺河向加速度的放大倍数几乎没有影响。对于高面板堆石坝,随岸坡坡度变缓,坝顶加速度最大值减少；处在宽阔河谷中的非高坝,河岸坡度对其顺河向加速度放大倍数几乎没有影响。对于中、高面板堆石坝,河岸陡峭时,河谷宽度对面板堆石坝顺河向加速度放大倍数有明显的影响,河谷越窄,加速度放大倍数就越大。研究了地震动特性对坝体地震反应的影响。随着基础输入加速度增加,面板堆石坝中心断面坝顶顺河向加速度放大倍数呈减小趋势。地震波频谱特性对坝体的加速度反应有较大的影响,其规律如下：坝体自振周期如果和输入的地震波卓越周期相近,则坝体加速度放大倍数较大；具有较宽频带的地震波对不同高度的面板堆石坝的加速度都有较大的放大作用。研究了面板堆石坝坝顶点顺河向加速度沿坝轴线的分布规律。结果表明,面板堆石坝坝顶点顺河向加速度沿坝轴线的分布规律表现为以坝中线为对称轴呈对称分布；在坝高相同、基础输入加速度不变情况下,随河谷宽度增加,坝顶点最大加速度位置由中间向两岸对称移动；对狭窄河谷,最大加速度在坝轴线中间坝顶部位,大于二维计算结果,对宽阔河谷,最大加速度在靠近两岸的部位,同样二维动力计算不能给出最大加速度位置。这一结果否定了以往对宽河谷采用二维动力计算结果的做法。进而提出对高面板堆石坝,地震反应除应给出沿坝高的地震放大系数外,还应给出沿坝轴线的地震放大系数。对面板堆石坝地震反应加速度分布规律进行了统计分析,给出了计算坝体最大加速度放大倍数的经验公式,为实际工程中进行基于拟静力法的面板堆石坝抗震稳定分析提供了参考依据。对两个实际面板堆石坝工程“四川硕曲河去学水电站混凝土面板堆石坝”和“山西西龙池抽水蓄能电站下库沥青混凝土面板堆石坝”进行三维有限元网格剖分,并进行了土石坝的三维非线性地震反应分析研究,特别是坝体的地震加速度分布的研究,以此验证工程的设计并为实际工程施工提供参考经验。更多还原

【Abstract】 As a serious natural disaster, severe earthquakes bring great losses to both property and life. Concrete faced rockfill dam, as a familiar type of dams, its instability is the most frequent reason between all of those who cause the break down. Nowadays, high rockfill dam construction is in the ascendance in China. Therefore, the antiseismic stability is the key factor for the engineering safety of the high rockfill dams and this research is important and exigent considering the latency risk of large reservoirs.The pseudo-static method stated in the criterion is widely used in antiseismic stability analysis of rockfill dams, and seismic coefficient is the key data in this method. But the criterion has been established in quite a early time and the data is mainly adopted form 2-D calculation, which nowadays cannot incarnate the seismic response of high rockfill dam, neither include the effect of valley shape and ground motion characteristic. With the development of computer science, large-scale 3-D finite element analysis of rockfill dams is now possible for the seismic characteristic research, especially the seismic coefficient research using 3-D finite element analysis to high rockfill dams, in providing the theoretic valuable data in theory and practice for the antiseismic analysis of the rockfill dams. A great quantity of calculation is performed to rockfill dams using the equivalent linear visco-elastic model, and statistical analysis is also realized.By the comparing analysis of the antiseismic stability methods of rockfill dams, the shear wedge method and the lumped-mass method can only be applied to limited boundary conditions; they cannot simulate dam-foundation system with different terrene situation and cannot simulate the dynamic shear stress distribution on the plane section. It is not enough if only use linear elastic model or visco-elastic model to situations that the rockfill material has obvious dynamic nonlinear character. The finite element method has the advantages of applicability to nonlinear heterogeneity problem, adaptation to complex boundary condition, applicability to static as well as dynamic calculation. Using finite element numerical method can obtain relative accurate solution for seismic response analysis of high rockfill dams.Using the above method, the effect of dam height, slope ratio and valley width to the seismic coefficient is studied. Especially, systematical analysis is performed to the acceleration distribution orderliness of the center section. Some meaningful conclusions are obtained. The amplification effect between 0-5/6H is relatively small. When the height is above 5/6H, the amplification effect will increase remarkably. When the valley is confined, the amplification effect at the top of a 300m-height dam is smaller than a 100m-height dam. When the valley is openness and the slope is cliffy, the dam height almost has no effect to the acceleration at the top of the dam. To high concrete faced rockfill dam, with the slope less cliffy, the maximum value of acceleration at the top of the dam becomes small. When the dam in a wide valley is not so high, the slope ratio almost has no effect to the amplification effect. But to high dams, when the slope is cliffy, the width of the valley has obvious effect to the amplification effect.The effect of earthquake characteristics to seismic response is also studied, and in the calculation four typical seismic waves are adopted. It is indicated that, with the increase of amplitude of acceleration inputted, the amplification effect at the top of the dam is diminished. This is because when the acceleration becoming larger, the shear stress becomes larger and the shear modulus becomes smaller. The spectrum characteristic of a seismic wave has great effect to the seismic acceleration response of the dam.The acceleration distribution along the dam axis at the top of the dam is studied. It is indicated that the acceleration distribution along the dam axis is symmetrical about the midline of the dam. With the valley width increasing, the maximum acceleration moves from the center section to the sideward section symmetrically. For confined valley, the maximum acceleration calculated using 3-D model is larger than that calculated using 2-D model. For wide valley, the maximum acceleration located at the place nearing the bank.2-D calculation cannot show the place where the maximum acceleration is happen. Therefor, the 2-D calculation is not anymore applicable for the wide valley because of the above results. It is commended that, to high rockfill dams, the seismic coefficient along the dam height as well as along the dam axis should be afforded.Statistical analysis is also made to the seismic coefficient, and an empirical equation for calculating the maximum acceleration is provided. Seismic stability analysis of rockfill dams using pseudo-static method can be modified according to the equation.Two actual projects of rockfill dam engineering are researched, they are’Quxue concrete faced rockfill dam on the Shuoqu River in Sichuan province’and’Xilongchi asphalt concrete faced rockfill dam in Shanxi province’. They are first meshes using 3-D finite element method, and then seismic response analysis is studied. The acceleration distribution of the dams is especially studied. The calculation result can prove the design scheme and offer some experiences to practical engineering construction.更多还原