乌东德大坝低热混凝土自生体积变形规律反馈分析研究

Feedback analysis of the autogenous volume deformation law of low heat cement concrete in Wudongde Hydropower Station

低热水泥混凝土在乌东德水电站全坝采用,为掌握大体积低热水泥混凝土的自生体积变形特点,本文基于乌东德大坝无应力计监测资料,利用大坝混凝土线胀系数反演值7.53×10^(-6)/℃,分离出自生体积变形数据,并结合自生体积变形试验数据,研究低热水泥混凝土的自生体积变形规律,分析结果显示:(1)各试验结果和反馈结果均显示自生体积变形普遍呈微膨胀变形,未见明显收缩;(2)90 d龄期自生体积变形平均值约23.19×10^(-6),180 d龄期约为31.90×10^(-6),200 d后变形大致稳定,增长速率明显变小,变形为35.22×10^(-6);(3)反演得到自生体积变形规律与试验结果略有不同,变化过程中的收缩阶段较短,且部分无应力计的反演结果明显偏大;(4)分析导致反演自生体积膨胀量存在差异的原因是线胀系数的取值和各坝段混凝土所经历的温度历程不同所致,不同的温度条件下混凝土水化速度的不同,进而引起自生体积变形过程不同。

Low-heat cement concrete is adopted in the whole dam of Wudongde Hydropower Station.In order to grasp the self-volume deformation characteristics of large volume low-fever cement concrete,in this paper,based on the stress-free strain meter monitoring data of Wudongde Dam and the inverse value of the linear expansion coefficient of dam concrete(7.53×10^(-6)/℃),the self-generated volume deformation data were separated.And combined with the self-generated volume deformation experiment data,studied the autogenous volume deformation law of low heat cement concrete.The main conclusions are as follows:(1)All test results and feedback results show that the autogenous volume deformation is generally micro-expansion deformation,and didn’t have obvious shrinkage;(2)The mean value of autogenous volume deformation is about 23.19×10^(-6)at the age of 90,31.90×10^(-6)at the age of 180 d,and 35.22×10^(-6)at the age of 200 d.After the age of 200 d,the autogenous volume deformation is roughly stable,and the growth rate is obviously smaller;(3)The inversion results of the self-generated volume deformation is slightly different from the experimental results,The shrinkage stage in the process of variation is short,and the inversion results of some stress-free samples are obviously larger;(4)The reasons that leads to the difference in the feedback volume are the values of linear expansion coefficient and the different temperature history experienced by concrete in each dam section.The hydration rates of concrete under different temperature conditions are different,thereby causing different autogenous volume deformation processes.