水工隧洞衬砌混凝土温控仿真计算理论方法改进研究

发布时间：2018-04-15 22:04

本文选题：衬砌混凝土 + 徐变　；参考：《武汉大学》2014年博士论文

【摘要】：水工隧洞衬砌混凝土的裂缝问题近些年来逐渐受到重视,以往研究表明,温度是引起衬砌混凝土裂缝的重要原因。相比一般的水工大体积混凝土,水工隧洞衬砌混凝土大多采用泵送技术,使得水泥用量大而导致绝热温升高；同时其又是薄壁结构,散热面和基础约束范围均较大；虽然散热快容易带走热量,但其半熟龄期小,最终使得最高温度出现时间短,且高峰过后的温降迅速,同时,在力学方面的重要因素徐变往往偏小,缓解局部应力集中的能力有限。大量工程资料表明,这些特点往往很容易导致温度裂缝的产生,因而需要进行温控防裂。温控防裂是一类极其复杂的技术问题,论文在前人研究的基础上,从混凝土重要力学因素徐变与松弛的计算理论方法、温度应力计算过程中的重要温控措施水管冷却的温度场有限元计算方法以及结合具体工程的衬砌混凝土水管冷却的具体温控措施等方面进行较为深入的研究,主要研究工作如下： 1.分析基于变系数广义开尔文模型的混凝土徐变力学基本方程,研究选取严格对应该模型和满足其物理意义的徐变度Dirichlet级数表达式,依据延迟范围理论,研究徐变计算模型各参数的优化选取,推导松弛系数率的表达式,提出用松弛系数率求解松弛系数,基于试验数据比较常用徐变度Dirichlet级数表达式与松弛系数的迭加算法。然后,分析基于延迟范围理论的徐变度模型对衬砌混凝土徐变及早期徐变温度应力计算的影响。 2.在变系数广义开尔文模型的基础上,提出综合考虑各元件系数受初始加载时间、观测时长、作用龄期和作用时长等影响的徐变模型,分析该模型的特点,并研究基于无再次加卸载条件下徐变模型各元件的特点及其在拟合精度上的优势。 3.分析并构建水管附近混凝土的热量平衡方程,采用等效热传导原理,推导水管附近任意区间内的平均温度,并在此基础上提出利用水管附近混凝土的温度梯度求解沿程温升的迭代算法,为提高求解固定网格尺寸下混凝土水管冷却的真实温度场的计算精度提供一种新的思路。 4.将混凝土通水冷却直接模拟法引入水工隧洞衬砌混凝土,研究施工期溪洛渡水工隧洞边墙衬砌混凝土采用水管冷却的温度场与现场对比情况。然后,以在建工程白鹤滩水电站导流洞无压段衬砌混凝土为例,采用水管冷却的有限元直接模拟法分析衬砌混凝土通水冷却的优势和不足,对衬砌混凝土水管冷却过程中的水管间距、通水水温和通水流量进行敏感性分析并提出有效的冷却参数优化方案,同时,提出解决不同水管间距下各代表处位置不在同一高度的分析方法,研究结果可为今后衬砌混凝土水管冷却的温控措施提供重要参考。
[Abstract]:In recent years, more and more attention has been paid to the cracks of lining concrete in hydraulic tunnels. Previous studies have shown that temperature is an important cause of cracks in lining concrete.Compared with the general hydraulic mass concrete, the hydraulic tunnel lining concrete mostly adopts pumping technology, which causes the increase of adiabatic temperature due to the large amount of cement, at the same time, it is a thin-walled structure with a large heat dissipation surface and a large restraint range of foundation.Although heat dissipation is easy to take away heat, its semi-mature age is small, resulting in a short maximum temperature and rapid temperature drop after the peak. At the same time, creep, an important factor in mechanics, tends to be small.The ability to relieve local stress concentration is limited.A large number of engineering data show that these characteristics often lead to temperature cracks, so temperature control and crack prevention are needed.Temperature control and crack prevention is a very complex technical problem. Based on the previous research, this paper presents a theoretical method for calculating creep and relaxation of important mechanical factors of concrete.The important temperature control measures in the process of temperature stress calculation, the finite element method of temperature field of water pipe cooling and the specific temperature control measures of concrete pipe cooling combined with concrete engineering are studied in depth.The main work of the study is as follows:1.The basic equations of concrete creep mechanics based on the generalized Kelvin model with variable coefficients are analyzed, and the Dirichlet series expressions of creep degree, which satisfy the physical meaning of the concrete creep model, are selected, according to the theory of delay range.The optimum selection of the parameters of creep calculation model is studied, the expression of relaxation coefficient rate is deduced, and the relaxation coefficient is solved by relaxation coefficient rate. Based on the experimental data, the superposition algorithm of creep degree Dirichlet series expression and relaxation coefficient is compared.Then, the influence of creep model based on the theory of delay range on the calculation of creep and early creep temperature stress of lining concrete is analyzed.2.Based on the generalized Kelvin model with variable coefficients, a creep model considering the influence of initial loading time, observation time, duration of action and duration of action on the coefficients of each component is proposed, and the characteristics of the model are analyzed.The characteristics of each component of creep model without reloading and unloading and its advantage in fitting accuracy are studied.3.The heat balance equation of concrete near the water pipe is analyzed and constructed, and the average temperature in any region near the pipe is deduced by using the equivalent heat conduction principle.On this basis, an iterative algorithm is proposed to solve the temperature rise along the process by using the temperature gradient of concrete near the water pipe, which provides a new way to improve the accuracy of calculating the real temperature field of concrete pipe cooling under fixed mesh size.4.The direct simulation method of water cooling of concrete was introduced into the lining concrete of hydraulic tunnel, and the temperature field of side wall lining concrete of Xiluodu hydraulic tunnel during the construction period was compared with that of the field.Then, taking the unpressurized lining concrete of diversion tunnel of Baihetan Hydropower Station under construction as an example, the advantages and disadvantages of water cooling of lining concrete are analyzed by using the finite element direct simulation method of pipe cooling.Sensitivity analysis of water pipe spacing, water temperature and flow rate during cooling process of lining concrete pipe is carried out, and an effective optimization scheme of cooling parameters is put forward, at the same time,This paper puts forward an analytical method to solve the problem that the position of each representative office is not at the same height under different water pipe spacing. The research results can provide an important reference for the temperature control measures of lining concrete pipe cooling in the future.
【学位授予单位】：武汉大学
【学位级别】：博士
【学位授予年份】：2014
【分类号】：TV554;TV544

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