【作者】 周华；

【导师】 徐斌；

【作者基本信息】 大连理工大学 ， 水利工程（专业学位）， 2021， 硕士

【摘要】 我国的水资源主要集中在西部地区,为有效利用水资源,不少高坝大库在该地区中规划筹建,其中包含多座面板堆石坝高度达到250m级。坝址区地质、地形条件复杂,地震烈度高、板块活动频繁,这对250～300m级特高面板堆石坝的抗震安全构成了巨大威胁。地震的突发性和不确定性是其固有属性,目前面板坝的抗震安全评价以确定性分析方法为主,不能考虑地震动随机性对结构响应的影响。此外,现行的国内外面板堆石坝抗震规范中均未对坝体沉降变形做出明确规定,因此开展考虑地震动随机性对面板堆石坝变形规律影响的研究对面板堆石坝抗震设计有较强的工程意义。针对上述问题,本文在国家自然科学面上项目“高土石坝随机动力分析与安全控制标准(No.51979026)”的资助下,采用随机动力分析方法,重点考虑了地震动的随机性,对四个250m级实际面板堆石坝工程进行了系统的数值模拟,研究了面板堆石坝在随机地震作用下加速度反应和堆石体沉降的概率分布规律,为高面板堆石坝的抗震设计和极限抗震能力的确定提供参考。主要工作如下:(1)基于谱表示-随机函数法并结合最新的水工抗震规范,建立了强度-频率全非平稳地震动模型,实现了快速生成具有丰富概率信息的地震动加速度时程样本;(2)考虑随机地震动样本量大小和有限元网格尺寸的敏感性对随机动力分析的影响。对不同随机地震动的样本量分组进行了对比,结果表明,样本量为144时的位移结果比大样本量时结果差异在2%以内;通过网格尺寸敏感性分析表明,10m网格的位移结果与2m相比,最大差异在5%以内,满足工程精度要求。(3)以古水、拉哇、大石峡和茨哈峡等四个实际面板堆石坝工程为研究对象建立了三维有限元模型并开展了系统的随机动力分析,利用概率密度演化理论和等价极值思想,研究了高面板堆石坝在不同强度(0.1g～1.0g)的随机地震作用下加速度和堆石体变形的概率密度信息和超越概率。综合4个工程的数值分析结果,建议了250m级高面板堆石坝基于沉降变形安全控制标准的极限抗震能力为0.7g～0.8g,为工程抗震设计提供参考。更多还原

【Abstract】 Water resources in China are mainly concentrated in the west region.In order to effectively utilize water resources,many high-dams and large reservoirs are planned and constructed in this area,including several concrete-faced rockfill dams(CFRDs)up to 250 m,these dam sites are characterized by high seismic intensity,frequent seismic activity and complicated geological and topographical conditions,and earthquakes are sudden and uncertain,which pose huge threats to the seismic safety of the 250m～300m ultra-high earth-rock dams.The suddenness and uncertainty of earthquake are its inherent properties.Currently,the seismic safety evaluation of face dam is mainly based on the deterministic analysis method,which cannot consider the influence of random ground motion on the structural response.In addition,the current seismic codes for face rockfill dams have not made explicit provisions on the settlement and deformation of the dam body.It is of great engineering significance to study the influence of random ground motion on the deformation law of concrete faced rockfill dams.In view of the above problems,this paper was supported by the National Natural Science Project "Standard for Stochastic Dynamic Analysis and Safety Control of High Earth-rockfill Dams(No.51979026)",which starts from the perspective of random dynamics and focuses on the randomness of ground motions.By generating random ground motion samples and performing amplitude modulation processing on them,numerical simulations are carried out on four 250m-level CFRDs.Establishing the seismic analysis method of concrete faced rockfill dams from the perspective of probability provides scientific basis for seismic design and ultimate seismic capacity analysis of high concrete faced rockfill dams.The main work is as follows:(1)Based on the spectral representation-random function method combined with the latest hydraulic seismic code,a strength-frequency non-stationary ground motion model is established and a time history sample of ground motion acceleration with rich probability information is generated quikly;(2)Consider the influence of random ground motion sample size and the sensitivity of finite element mesh size on random dynamic analysis.The sample size grouping of different random ground motions is compared,and the results show that the displacement results when the sample size is 144 are within 2% of the results when the sample size is large;the sensitivity analysis of the grid size shows that the displacement of the 10 m grid Compared with 2m,the maximum difference is within 5%,which meets the engineering accuracy.(3)Taking Gushui,Rawa,Dashixia and Cihaxia as the research objects,three-dimensional finite element models are established to carry out stochastic dynamic analysis,using probability density evolution theory and equivalent extreme value ideas,The probability density information and probability of exceedance of acceleration and rockfill deformation under random earthquakes with different strengths(0.1g～1.0g)of high-face rockfill dams are studied.Based on the numerical analysis results of 4 projects,it is recommended that the ultimate seismic capacity of 250m-level high-face rockfill dams based on the settlemen safety control standards is 0.7g～0.8g,which provides a reference for the seismic design of projects.更多还原