【作者】 周扬；

【导师】 孔宪京； 邹德高；

【作者基本信息】 大连理工大学 ， 水工结构工程， 2012， 博士

【摘要】 目前我国西南强震区一大批高土石坝项目在建或待建。由于混凝土面板堆石坝具有安全、经济以及适应性强的特点,在建或拟建的土石坝中有相当一部分采用了面板堆石坝方案。这些高面板堆石坝坝址区河谷条件和地质条件复杂,地震活动频繁且烈度较高。因此,开展强震作用下高面板堆石坝的抗震对策研究具有重大的理论价值和工程意义。2008年5月12日,距离紫坪铺面板堆石坝以西约17km的四川省汶川县发生了8.0级强烈地震,震中最大烈度高达Ⅺ度。紫坪铺大坝在地震中出现了明显的震损破坏。但紫坪铺大坝台阵没有获取到强震时坝址基岩处地震动记录,大坝的动力计算成果无法在定量上与实测资料进行对比。地震作用下筑坝材料的动力本构模型,目前国内外大多采用等价线性粘-弹性模型描述高土石坝的地震反应。因此,建立适用于高土石坝应力应变特性的弹塑性分析方法,反应强震时大坝渐进变形过程具有重要的意义。本文在国家自然科学基金项目“强震区高土石坝抗震措施研究”(编号：50679093)、国家自然科学基金重大研究计划重点项目“高土石坝地震灾变模拟及安全控制方法研究”(编号：90815024)和“十一五”国家科技支撑计划项目“紫坪铺水库震损评估与抗震减灾技术研究”(编号：2009BAK56B02)资助下,结合汶川地震紫坪铺大坝的震害情况,对大坝的地震变形与面板错台进行了数值仿真,建立了高面板堆石坝弹塑性静、动力计算方法。论文的主要内容包括以下几方面：(1)对汶川地震后紫坪铺面板堆石坝余震记录的加速度峰值及频谱特性等进行了分析。选择坝址基岩台站实测余震地震波作为大坝地震动输入,对紫坪铺大坝进行了三维动力有限元分析,并将计算得到的坝体加速度与台站的监测数据进行了对比,研究了小震时大坝的动力反应规律。(2)对汶川地震紫坪铺面板堆石坝动力反应分析时的地震动输入选择问题进行了探讨。分别选取几组基岩台站实测主震波、紫坪铺台站某实测余震波以及按水工抗震规范人工生成地震波等作为数值计算的地震动输入,对紫坪铺大坝进行三维动力有限元分析,并与实测结果进行对比,结合大坝自振反应的基本规律,分析大坝在各组地震动作用下的动力反应特性,建议汶川地震中紫坪铺大坝动力计算时可选择茂县地办实测主震波或规范谱人工生成地震波作为地震动输入。(3)对汶川地震紫坪铺大坝的震害现象进行了数值仿真。采用三维有限元分析方法计算了大坝地震永久变形,并与实测值进行对比；分别采用了基于应变势的永久变形分析方法和刚体滑块法,对大坝二、三期面板施工缝处的错台现象进行了数值模拟,研究了面板错台的机理,并与面板实际错台震害进行对比,分析了施工缝方向、水库水位以及不同地震动等因素对面板错台的影响。(4)建立了高面板堆石坝的弹塑性静、动力分析方法。考虑筑坝堆石料的压力相关性和滞回特性,对广义塑性P-Z模型的弹性剪切模量、弹性体积模量、加卸载塑性模量和应力历史再加载函数进行了修改,并根据筑坝堆石料静力和循环荷载试验确定了修改后的模型参数。将改进的广义塑性P-z模型加入到有限元计算软件GEODYNA中,实现了基于弹塑性模型的高面板堆石坝有限元计算静、动力计算方法。采用该模型,对紫坪铺大坝进行有限元静、动力反应计算,模拟了竣工期和地震中大坝变形和面板施工缝错台的渐进变化过程。(5)建议了改善面板应力的综合抗震对策。通过对不同坝高、不同河谷形状的高面板堆石坝进行三维静、动力有限元分析,研究了高面板堆石坝震前、地震时以及地震后面板应力的分布规律。通过不同抗震方案的对比,建议了挤压边墙施工、降低面板与边墙摩擦、面板竖缝填充材料优化布置的综合面板应力改善对策,并进行了数值验证。更多还原

【Abstract】 A lot of high earth and rock dams have been constructed or being planned or designed in the western region of China (meizoseismal area). With advantages in safety, economy and adaptability, Concrete Face Rockfill Dams (CFRD) are selected as one of the most widely used rockfill dam types. Many of these high CFRDs located at valleys with extremely complex geological conditions, and at regions where earthquake with high seismic intensity occurred frequently. Therefore, it has great theoretical practical significances to study the aseismic measures of high CFRDs to survive from strong earthquakes.A large earthquake (Ms=8.0) occurred on May12,2008in Wenchuan in China’s Sichuan province,17km west from where locates Zipingpu CFRD. The largest seismic intensity in the epicenter was up to XI. The strong shock caused obvious damages on Zipingpu dam. Unfortunately the rock station under Zippingpu dam failed to capture the base rock seismic wave of Zippingpu dam during Wenchuan earthquake. Thus the damages from field investigations cannot be used to quantitatively verify the results predicted by dynamic numerical analysis. Equivalent linear viscoelastic model was usually applied in dynamic constitutive model of rockfill materials. Therefore, the elastic-plastic analysis method was established for the stress-strain behavior of high earth and rockfill dam. It is a great significance to calculate the process of gradual deformation during earthquake.The present research is supported by the Natural Science Foundation of China "Study on aseismic measures of high earth and rockfill dam in meizoseismal area"(No.50679093), the National Mega-project of Natural Science Foundation of China "Disaster simulation and safety control of high earth and rock dams during earthquake"(No.90815024) and the National Key Technology R&D Program for the11th5-year plan "Study on earthquake damage assessment of Zipingpu reservoir and aseismic technology of dams"(No.2009BAK56B02). The deformation of Zipingpu dam and the dislocations of face slabs at horizontal construction joints were simulated by numerical method. A elasto-plastic model for static and dynamic analyses on high rockfill dams was developed and verified. The main contents of this study are as follows:(1) The peak acceleration and spectrum characteristic of the dynamic responses of Zipingpu CFRD shaken by aftershocks after Wenchuan Earthquake were analyzed. Several representative motion records captured by the rock stations at the dam site were selected to generate the seismic input for three-dimensional dynamic finite element (FE) analysis of Zipingpu CFRD. The calculated acceleration responses were compared with the measured data at different levels. The characteristic of dynamic response of the dam under small earthquake was studied.(2) Selection of the seismic wave input of Zipingpu CFRD in dynamic simulation under Wenchuan earthquake was discussed at first in this paper.3-D dynamic FE simulations of Zipingpu CFRD were carried out with various seismic input waves, including records of main shock captured by nearby rock stations, records of aftershocks captured by stations on the dam site, and the artificially derived seismic input according to the standardized spectrum of specifications for seismic design of hydraulic structures. The dynamic responses of the dam under various seismic input waves are compared with the measured data. Suitable seismic wave inputs of Zipingpu CFRD under Wenchuan earthquake such as seismic waves measured by Diban station of Mao town and artificial seismic waves generated by standardized spectrum were suggested for dynamic simulation.(3) The damages of Zipingpu dam during Wenchuan earthquake were simulated numerically. Three-dimensional FE methods, respectively based on strain potentials and rigid sliding method, were adopted to calculate the permanent deformation of the dam and further to calculate the dislocations of face slabs between the second and third construction stages. The calculated results are compared with the field measured data. The major factors affecting the dislocation of face slabs, including the direction of the joints, water level of the reservoir and different seismic inputs, were analyzed.(4) An elasto-plastic model for static and dynamic FE analyses of high CFRD was developed based on the generalized plastic P-Z model. The elastic shear modulus, elastic bulk modulus, loading and unloading plastic modulus, and and reload function about stress history were modified according to the stress-related behaviour and the damping characteristic of rockfill materials. The parameters of the improved model were determined by large-scale static and dynamic triaxial experiments. The improved generalized plastic P-Z model was successfully programmed into the FE software GEODYNA. Static and dynamic analyses of Zipingpu dam were carried out using this elasto-plastic model. The dam deformation during construction and during the earthquake, and the dislocations of face slabs between construction stages during the earthquake were calculated.(5) Comprehensive aseismic measures for improving the stresses distributions of face slabs were proposed, including adopting extrusion-sidewall technology during construction, reducing the friction factor between sidewalls and face slabs, and adopting optimization scheme in the filling materials between vertical joints. The stress distribution behaviour of face slabs of high CFRD before, during and after earthquake were investigated by3-D staic and dynamic FE analyses. The effects of various dam height and valley shape were also discussed. The results of FE analyses showed that the above aseismic measures can effectively improve the stress distribution of the face slabs of CFRDs.更多还原