层面抗剪断参数对碾压混凝土坝稳定性的影响

发布时间：2018-10-29 17:57

【摘要】：我国目前水电装机刚超过2亿千瓦,规划装机到2050年将超过5亿千瓦；大型水利水电工程建设主要有三种坝型可以选择：堆石坝、常态混凝土坝、碾压混凝土坝。碾压混凝土坝发展最快。相比于常态混凝土坝,碾压混凝土坝优势主要在于：(1)工程造价低；(2)建坝周期短；(3)环保适应性强。然而,薄层碾压的施工工艺使得碾压混凝土坝与常态混凝土坝相比具有独特的成层结构力学特性。尤其是在地震作用下,容易形成表面裂缝和贯穿型裂缝,继而出现滑动,最终影响大坝的整体稳定性。因此,有必要研究在地震作用下碾压混凝土坝成层特性对其抗滑稳定性的影响。基于此,本文展开了一系列研究,具体内容如下： (1)采用有限元法分析了某碾压混凝土重力坝典型坝段在地震作用下沿碾压层面、建基面的抗滑稳定性,确定了坝段的主要薄弱部位以及比较薄弱的层面。通过地震动超载分析计算坝体非线性模型各计算层面的最小抗滑稳定系数,并得到层面的抗滑稳定系数与地震动超载倍数k的关系曲线,得到了碾压混凝土重力坝超载潜力。运用强度折减法计算坝体非线性模型各计算层面的最小抗滑稳定系数,并得到层面的抗滑稳定系数与强度折减系数k的关系曲线,得到了碾压混凝土坝的强度储备系数。 (2)碾压混凝土采用层铺施工,会导致坝体存在许多水平层面。如果层面结合能力比较差,层面的抗剪断参数和坝体本身的抗剪断参数存在较大差异,这种差异会直接影响坝体的整体稳定性。本文将线弹性有限元时程分析与模拟退火算法结合起来,基于应力场定义抗滑稳定安全系数,应用模拟退火算法搜索碾压重力坝在地震作用下最脆弱滑动面及相应的安全系数,进而得到不同层面抗剪断参数对碾压混凝土坝滑动面形状及抗滑稳定安全系数的影响,并与常态混凝土坝进行了对比。 (3)碾压混凝土坝在强震作用下不可能一直处于线弹性工作状态,坝体混凝土会出现一定的损伤。本文采用塑性损伤模型,对碾压混凝土坝进行了时程分析,提取了应力场,继而研究了层面抗剪断参数对碾压混凝土坝滑动面及抗滑稳定安全系数的影响,并与线弹性模型得到的结果做了对比。
[Abstract]:At present, the hydropower installation in China is only more than 200 million kilowatts, and the planned installation will exceed 500 million kilowatts by 2050. There are three main dam types for large-scale water conservancy and hydropower projects: rockfill dam, normal concrete dam and roller compacted concrete dam. Roller compacted concrete dam develops fastest. Compared with normal concrete dam, RCC dam has the following advantages: (1) low project cost; (2) short construction period; (3) strong environmental protection adaptability. However, the construction technology of thin layer compaction makes RCC dam have unique mechanical properties of stratified structure compared with normal concrete dam. Especially in the earthquake, surface cracks and penetrating cracks are easily formed, and then sliding, which ultimately affects the overall stability of the dam. Therefore, it is necessary to study the influence of stratification characteristics of RCC dams on the stability of RCC dams under earthquake. Based on this, a series of studies are carried out in this paper. The main contents are as follows: (1) the stability of a typical section of a RCC gravity dam under seismic action along the roller compacted plane is analyzed by using finite element method (FEM). The main weak position and relatively weak layer of dam section are determined. Through the analysis of ground motion overload, the minimum anti-slip stability coefficient of each layer of nonlinear model of dam body is calculated, and the relation curve between the anti-slide stability factor and the overload multiple k of ground motion is obtained, and the overload potential of roller compacted concrete gravity dam is obtained. Using the strength reduction method to calculate the minimum anti-slide stability coefficient of each layer of nonlinear model of dam body, the relationship curve between the stability coefficient and the strength reduction coefficient k is obtained, and the strength reserve coefficient of the roller compacted concrete dam is obtained. (2) there are many horizontal layers in the dam body. If the layer binding capacity is poor, there is a great difference between the shear parameters of the plane and the shear parameters of the dam itself, which will directly affect the overall stability of the dam. In this paper, the linear elastic finite element time-history analysis is combined with simulated annealing algorithm. Based on the definition of anti-slip stability safety factor in stress field, simulated annealing algorithm is used to search the most vulnerable sliding surface and the corresponding safety factor of roller compacted gravity dam under earthquake action. The influence of different shear failure parameters on the shape of sliding surface and the safety factor of sliding stability of RCC dam is obtained and compared with that of normal concrete dam. (3) it is impossible for RCC dam to be in linear elastic working state under strong earthquake, and the concrete of RCC dam will be damaged to some extent. In this paper, the plastic damage model is used to analyze the time history of RCC dam, the stress field is extracted, and the influence of shear failure parameters on the sliding surface and safety factor of RCC dam is studied. The results obtained by the linear elastic model are compared with those obtained by the linear elastic model.
【学位授予单位】：大连理工大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV642.2

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