高拱坝封拱过程优化分析研究

发布时间：2018-12-17 13:54

【摘要】：近些年拱坝设计理论和方法不断提高,施工经验不断积累,我国规划与修建了一批高拱坝。因为高拱坝"边浇筑边封拱"的施工特点,其封拱过程与大坝混凝土温度控制、拱坝受力初始条件、计入施工过程影响的应力变形分布,独立坝段悬臂受力高度以及大坝施工进度等因素密切相关。拱坝在接触灌浆前需要重点关注混凝土浇筑层的温度控制与横缝开度问题,而(特)高拱坝又有独特的特点。在温度控制方面,不仅要求灌区在接缝灌浆前通过温控措施达到相应的封拱温度,沿坝段高程还需要做好温度梯度控制工作。在悬臂高度控制方面,高拱坝施工期,若浇筑安排不当容易造成悬臂高度过高,不仅可能在悬臂梁根部产生大的拉应力,也影响着坝段之间横缝的开合度,而横缝开度影响着接缝的可灌性。因此,有必要对高拱坝封拱过程当中涉及的工程问题进行优化。本研究基于乌东德电站已有工程和试验资料,选取封拱施工过程中涉及的三个典型工程问题,采用有限元方法,考虑混凝土温度控制和大坝施工期受力条件,提出优化思路以及优化方案,具体研究内容如下:(1)接缝灌浆区高度优化分析参考原接缝灌浆区高度方案,依据适当增加自由区灌浆范围的原则,拟定了对比灌浆方案。综合考虑坝体浇筑、温度控制和接缝灌浆过程全阶段。结果表明增加灌浆范围有增强坝段之间约束的趋势并且实际施工中若有加快施工进度和精简灌区的需要时,可以适当增加自由区浇筑块的灌区高度。(2)同冷区高度空间动态优化分析提出同冷区高度时空控制的思路,对典型坝段的基础约束区、自由区、孔口约束区拟定不同的同冷区高度方案并进行敏感性分析,计算分析结果表明:同冷区高度越大,已灌区应力最大值呈现减小的趋势,并且对于弱约束区,同冷区高度的影响有限。根据计算结果还拟定了乌东德高拱坝推荐同冷区高度方案。(3)高拱坝悬臂高度个性化控制提出悬臂梁高度个性化控制思路,综合考虑最高温度、最大应力及横缝开度的控制标准,仿真计算表明:在重力荷载的作用下,第一主应力随悬臂梁高度增大而增大;另外,外界气温回灌为悬臂高度影响横缝开度的初步原因。根据评价标准确定了乌东德拱坝7#坝段各特征高程处的悬臂梁最大允许高度。
[Abstract]:In recent years, the design theory and method of arch dams have been improved, and the construction experience has been accumulated. A number of high arch dams have been planned and built in China. Because of the construction characteristics of high arch dam, the process of arch sealing and the temperature control of dam concrete, the initial stress condition of arch dam, and the distribution of stress and deformation affected by construction process are taken into account. The cantilever height and the construction schedule of the independent dam are closely related to each other. Before the contact grouting, the arch dam should pay attention to the temperature control and the transverse joint opening of the concrete pouring layer, and the (extra) high arch dam has its unique characteristics. In the aspect of temperature control, it is not only required that the temperature control measures should reach the corresponding temperature of arch sealing before the joint grouting, but also the temperature gradient control work should be done along the height of the dam section. In the aspect of cantilever height control, if the construction arrangement of high arch dam is not proper, the cantilever height will be too high, which will not only produce large tensile stress at the root of the cantilever beam, but also affect the opening and closing degree of the transverse joint between the dam sections. The opening of the transverse seam affects the irrigability of the joint. Therefore, it is necessary to optimize the engineering problems involved in the arch sealing process of high arch dams. Based on the existing engineering and experimental data of the Wudongde Hydropower Station, three typical engineering problems involved in the arch sealing construction are selected, and the finite element method is adopted to consider the concrete temperature control and the stress condition during the dam construction period. The main contents of this paper are as follows: (1) the height optimization of joint grouting area is analyzed by referring to the original joint grouting area height scheme, and according to the principle of increasing the grouting range of free zone properly, the comparative grouting scheme is drawn up. The whole process of dam pouring, temperature control and joint grouting is considered comprehensively. The results show that increasing the grouting range has the tendency of increasing the constraint between dam sections, and if there is a need to accelerate the construction progress and streamline the irrigation area in actual construction, (2) the spatial dynamic optimization analysis of the height of the same cold zone puts forward the idea of space-time control of the height of the same cold zone. Different height schemes of the same cooling zone were worked out and sensitivity analysis was carried out. The results of calculation and analysis showed that the greater the height of the same cooling zone, the smaller the maximum stress of the irrigated area was, and for the weakly confined zone, the maximum stress of the irrigated area decreased with the increase of the height of the same cooling zone. The influence of the height of the same cold zone is limited. According to the results of calculation, the recommended height scheme for the same cooling zone of Wudongde High Arch Dam is drawn up. (3) the individualized control of cantilever height of high arch dam is put forward, and the maximum temperature is considered synthetically. The simulation results show that the first principal stress increases with the height of the cantilever beam under the action of gravity load. In addition, the external air temperature recharge is the primary reason for the influence of cantilever height on transverse joint opening. According to the evaluation criteria, the maximum allowable height of cantilever beam at each characteristic elevation of Udongde arch dam was determined.
【学位授予单位】：武汉大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TV642.4

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