基于等效龄期的碾压混凝土重力坝温度应力场数值分析

发布时间：2018-06-29 03:51

本文选题：碾压混凝土 + 重力坝　；参考：《浙江大学》2014年硕士论文

【摘要】：近年来碾压混凝土重力坝在国内外的水电工程中被广泛应用,然而坝体在施工期的开裂现象依旧存在,最主要的一个原因就是温度应力。因此有必要对坝体进行精细的数值耦合分析,比较坝体各部位应力对温度的敏感性。本文为了验证混凝土强度对温度的敏感性,先基于Arrhenius函数等效龄期方法,进行了水工混凝土在不同养护温度下的强度试验,验证了等效龄期方法的适用性。然后在参考龙滩碾压混凝土坝原材料试验数据资料的基础上,拟合了碾压混凝土弹性模量、徐变度、劈裂抗拉强度与龄期之间的相互关系。根据碾压混凝土分层上升浇筑的特点,运用大型通用有限元ANSYS软件中的生死单元模块、参数化设计语言APDL命令流技术,实现了碾压混凝土重力坝挡水坝段复杂随机施工过程的数值模拟,并用现场温度实测数据加以验证；另外,不同的浇筑温度和夏季停工因素也在温度场结果分析中加以比较。应力场分析时,本文首次将普通混凝土中的Arrhenius函数等效龄期理论引入碾压混凝土重力坝温度应力场分析中；并因此选择了2种不同的计算方案,以对比实际龄期、等效龄期这2种计算方案对坝段应力场分布的不同影响,并采用开裂系数评价坝体各部位开裂风险对温度的敏感性,从而反映温度对碾压混凝土坝体材料性能的影响。计算结果表明,考虑等效龄期时,相比实际龄期,能大幅度减少各高程节点拉应力峰值。而不管采用何种方案,高温季节施工层面的外部节点都有较明显的拉应力峰值,而低温季节施工层面的外部节点拉应力峰值则很小。考虑实际龄期时,施工期y方向应力最大值均出现在坝体的基础强约束区。而考虑等效龄期时,y方向应力呈现明显的纵向分布特征,而不再是沿坝高方向的季节性特征,基础强约束区和基础弱约束区y方向应力值也较小。考虑实际龄期时,基础强约束区中心节点沿y方向的后期开裂指数较大,如果不采取防护措施,就会产生基础部位水平裂缝。当考虑等效龄期时,各高程中心节点均不会发生沿顺河向的垂直裂缝,更绝对不会在碾压层面产生水平裂缝。等效龄期的计算方法重新评估了坝段各部位尤其是基础强约束区的开裂风险,表明温度对碾压混凝土重力坝材料性能和各部位的应力分布有着明显影响。
[Abstract]:In recent years, RCC gravity dams have been widely used in hydropower projects at home and abroad. However, the cracking of the dam body during the construction period still exists, one of the main reasons is the temperature stress. Therefore, it is necessary to carry on the fine numerical coupling analysis to the dam body, and to compare the sensitivity of the stress of each part of the dam body to the temperature. In order to verify the temperature sensitivity of concrete strength, based on the Arrhenius function equivalent age method, the strength tests of hydraulic concrete at different curing temperatures are carried out, and the applicability of the equivalent age method is verified. Based on the experimental data of RCC dam, the relationship between the elastic modulus, creep degree, splitting tensile strength and age of RCC is fitted. According to the characteristics of RCC layered upward pouring, using the birth and death element module in the large-scale finite element ANSYS software, the parameterized design language APDL command flow technology is used. The numerical simulation of complex random construction process of RCC gravity dam section is realized and verified by field temperature data. In addition, different pouring temperatures and summer shutdown factors are compared in the analysis of temperature field results. When the stress field is analyzed, the equivalent age theory of Arrhenius function in ordinary concrete is introduced into the analysis of thermal stress field of RCC gravity dam for the first time, and two different calculation schemes are selected to compare the actual age of RCC gravity dam. The two calculation schemes of equivalent age have different effects on the stress field distribution of the dam segment, and the cracking coefficient is used to evaluate the sensitivity of the cracking risk of the dam body to the temperature so as to reflect the influence of temperature on the material properties of the RCC dam body. The results show that when the equivalent age is considered, the peak tensile stress of each elevation node can be greatly reduced compared with the actual age. However, no matter what scheme is adopted, the peak tensile stress of the external node at the construction level in the high temperature season is obvious, but the peak value of the tensile stress in the construction layer in the low temperature season is very small. When considering the actual age, the maximum value of stress in the direction of y appears in the strong restraint zone of the dam foundation during the construction period. Considering the equivalent age, the stress in the y direction shows obvious longitudinal distribution, but is no longer seasonal along the direction of the height of the dam, and the stress value in the y direction of the strong constraint zone and the weak constraint zone of the foundation is also smaller. When considering the actual age, the later cracking index of the center node in the strong restraint zone of the foundation along the y direction is large, and if the protective measures are not taken, the horizontal crack in the foundation will occur. When the equivalent age is considered, the vertical cracks along the river direction will not occur in each elevation center node, and the horizontal cracks will not be produced in the rolling layer. The calculation method of equivalent age reevaluates the cracking risk in every part of dam section, especially in the strongly confined zone of foundation. It shows that temperature has a significant effect on the material performance and stress distribution of RCC gravity dam.
【学位授予单位】：浙江大学
【学位级别】：硕士
【学位授予年份】：2014
【分类号】：TV642;TV315

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