Numerical analysis of dislocations of the face slabs of the Zipingpu Concrete Faced Rockfill Dam during the Wenchuan earthquake

The Zipingpu Concrete Faced Rockfill Dam （CFRD） was obviously damaged during the Wenchuan earthquake in 2008. A wide range of dislocations occurred along the horizontal construction joints at EL. 845m, between the face slabs constructed in the second and third stages. The maximum displacement of the dislocations reached 17cm. In this study, the slab dislocations were investigated using finite element （FE） analysis. The method based on strain potential was applied to compute the permanent deformation of the Zipingpu Dam during the Wenchuan earthquake. The calculated magnitude of the slab dislocation showed good agreements with the field measurements. The dislocation mechanism was discussed. The results show that the dislocation of the concrete slab is a subsequent damage after the permanent deformation of the rockfill materials. The effects of the shear strength and the direction of the construction joints, the reservoir water level and the seismic waves were studied. The shear strength and the direction of the construction joints, reservoir water level and have a significant effect on the dislocation displacement. The dislocation can be effectively reduced by measures such as changing the direction of the construction joints or improving the shear strength at the horizontal joints.

Analysis on residual strain of Zipingpu Concrete Faced Rockfill Dam after Wenchuan earthquake

The Zipingpu Concrete Faced Rockfill Dam （CFRD） was subjected to significant local damage in the ＂5.12＂ Wenchuan earthquake. It is the first rockfill dam of more than one hundred meters high to encounter a strong earthquake anywhere in the world. Based on the finite element smoothing method, the residual strains at a typical cross-section and a downstream slope of the dam were obtained by processing the dam monitored displacement data. The position of and reason for the dam settlement and deformation ofrockfill dilatancy in the earthquake were analyzed according to the section residual strain. The results show that the maximum settlement ratio on the dam body approximately occurs at 2/3 of the dam height; dilatancy occurs from the dam crest to 25-30 m in the upstream and downstream slope; the immediate cause of the face slabs horizontal construction joint dislocation is excessive residual shear strain. Meanwhile, the position of and reason for the dam fissure in the earthquake were analyzed according to the dam slope residual strain.

土石坝坝顶加固的永久变形机理及其离心模型试验验证

首先介绍了汶川特大地震中紫坪铺大坝永久变形原型观测的研究结果,根据紫坪铺大坝汶川地震实测结果,发现地震永久变形主要产生于大坝的上部,从地震永久变形的发生机理论证了坝顶加固技术的合理性与科学性.然后介绍了土石坝离心模型动力试验的研究成果,通过离心模型试验验证了坝顶加固的有效性与合理性.通过比较,表明离心模型试验得到的大坝变形分布形态、大坝外形轮廓变化、变形矢量等关键技术特性与墨西哥El Infiernillo土石坝及紫坪铺汶川地震实测结果吻合很好,证实了离心模型试验的技术优势.

“5·12”汶川地震紫坪铺面板堆石坝静动力初步反演研究

根据"5·12"汶川地震峰值加速度衰减关系,推求坝址基岩EW、NS、UD方向峰值加速度分别为0.52g、0.46g、0.43g,然后采用比例法将实测加速度记录(051MXT)换算得到紫坪铺大坝动力计算的输入加速度时程;在利用建设阶段变形监测资料反演堆石体静力模型参数得到大坝静应力的基础上,结合吉林台、猴子岩等工程室内试验资料类比得到了堆石体反映振动硬化特性动力模型的初步参数,并结合关门山、察汗乌苏等工程的现场原位试验资料和大坝实测地震加速度的频谱特性进行了调整复核;通过计算输入地震加速度的等效振动周数,利用实测资料对大坝堆石体的永久变形参数进行了反演分析。结论认为:振动硬化动力模型反映了大坝堆石体地震过程中的"震缩"现象,"5·12"汶川地震主震时间较长和坝址近震的铅直向加速度较大,是紫坪铺大坝震后永久变形较大的主要原因,Ⅱ、Ⅲ期混凝土面板的错台由于堆石体永久变形引起的次生破坏。现有土石坝动力分析理论和方法基本可以反映土石坝的抗震性能。

汶川地震中紫坪铺面板坝抗震特性初步分析

紫坪铺大坝为"5.12"汶川特大地震中高地震烈度区的最高坝,其设计和施工富有特色。调查表明,大坝基本蓄水功能没有受到大的影响,上下游坝坡稳定安全,震损表现为总体震损轻微,局部震损较重。分析认为,坝体的变形稳定、抗滑稳定和渗透稳定性能良好,震损可修复和易修复,地震动输入模式有别于常规模式。抗震特性初步分析可得到几点重要的经验和启示。

紫坪铺面板坝加速度地震反应振动台模型试验研究

混凝土面板堆石坝的加速度地震反应是其设计和运行中参考的主要依据之一。由于数值方法难以准确模拟土石填筑材料的复杂特性,振动台模型试验被应用于高面板坝坝体的加速度地震反应研究。本文通过对紫坪铺面板堆石坝的大型振动台三维模型试验,得到不同地震动工况下加速度在坝体中的分布以及加速度放大倍数沿坝高的分布。研究发现,在输入加速度幅值较低时坝体的加速度放大倍数最大值出现在0.8倍坝高左右,放大倍数随着输入地震动幅值的增大而减小,并且放大倍数极值出现位置逐渐上移到坝顶。相同高程测点的加速度反应,下游坡面最大,坝体内部加速度小于坝体表面加速度。

世界首次近距离检验高面板堆石坝的抗震安全性——兼论面板坝的抗震性能

紫坪铺高面板坝经受了"5·12"汶川8级地震的检验,结合受震后的某些原型观资料分析,从稳定、变形、渗流3方面而言,大坝都是安全的。这是世界上第1座高面板坝近距离经受了地震烈度约10度的强震考验,为以后在地震影响区水利、水电枢纽工程的勘测设计选址和坝型选择提供了宝贵的经验。还结合面板坝的某些抗震稳定分析及其他面板坝受震的情况,论证了面板坝优越的抗震性能。

基于变形控制标准的高土石坝地震可靠度分析

基于可靠度分析的设计方法是科学定量地研究和保证岩土工程安全性的重要手段之一。通过定量考察土石坝工程中的不确定性因素,综合评估地震失效概率,可为高土石坝抗震设计和风险评估提供参考。以坝顶震陷率作为地震安全控制指标,提出了同时考虑地震和筑坝料参数不确定性的高土石坝地震可靠度分析方法。首先,采用地震烈度作为地震危险性的宏观衡量尺度,通过引入地震烈度概率模型,将基于概率烈度的地震动峰值作为地震强度因子,调整规范谱人工地震波的幅值进行动力有限元计算。然后,采用适用于处理小样本和非线性问题的高斯过程响应面法,建立筑坝料参数与坝顶震陷率之间的非线性映射关系,结合蒙特卡罗法计算高土石坝地震失效概率。最后,以紫坪铺面板堆石坝为例,应用该方法考察了设计基准期内的地震失效概率。

Seismic responses of high concrete face rockfill dams:A case study

Seismic responses of the Zipingpu concrete face rockfill dam were analyzed using the finite element method. The dynamic behavior of rockfill materials was modeled with a viscoelastic model and an empirical permanent strain model. The relevant parameters were obtained either by back analysis using the field observations or by reference to parameters of similar rockfill materials. The acceleration responses of the dam,the distribution of earthquake-induced settlement, and the gap propagation under the concrete slabs caused by the settlement of the dam were analyzed and compared with site investigations or relevant studies. The mechanism of failure of horizontal construction joints was also analyzed based on numerical results and site observations. Numerical results show that the input accelerations were considerably amplified near the top of the dam, and the strong shaking resulted in considerable settlement of the rockfill materials, with a maximum value exceeding 90 cm at the crest.As a result of the settlement of rockfill materials, the third-stage concrete slabs were separated from the cushion layer. The rotation of the cantilever slabs about the contacting regions, under the combined action of gravity and seismic inertial forces, led to the failure of the construction joints and tensile cracks appeared above the construction joints. The effectiveness and limitations of the so-called equivalent linear method are also discussed.

紫坪铺大坝坝顶护栏震损情况及启示

汶川地震中紫坪铺面板堆石坝经受了强震的考验,地震导致坝顶护栏发生了严重破坏,其破坏具有一定规律性。本文对坝顶护栏混凝土柱的震损情况进行了统计和分析,发现几乎所有震坏倒塌的混凝土柱均是从根部发生断裂,其倒塌方向基本垂直于坝轴线,且成规律性的向上游或者下游倒塌。文中分析了混凝土柱倒塌规律的可能原因,指出坝顶护栏混凝土柱的震损情况可以为今后深入研究该堆石坝的地震波输入及震动响应规律性提供一些参考依据和启示。