本文選題：襯砌混凝土 + 徐變��； 參考：《武漢大學(xué)》2014年博士論文

【摘要】：水工隧洞襯砌混凝土的裂縫問題近些年來逐漸受到重視,以往研究表明,溫度是引起襯砌混凝土裂縫的重要原因。相比一般的水工大體積混凝土,水工隧洞襯砌混凝土大多采用泵送技術(shù),使得水泥用量大而導(dǎo)致絕熱溫升高；同時其又是薄壁結(jié)構(gòu),散熱面和基礎(chǔ)約束范圍均較大；雖然散熱快容易帶走熱量,但其半熟齡期小,最終使得最高溫度出現(xiàn)時間短,且高峰過后的溫降迅速,同時,在力學(xué)方面的重要因素徐變往往偏小,緩解局部應(yīng)力集中的能力有限。大量工程資料表明,這些特點往往很容易導(dǎo)致溫度裂縫的產(chǎn)生,因而需要進(jìn)行溫控防裂。溫控防裂是一類極其復(fù)雜的技術(shù)問題,論文在前人研究的基礎(chǔ)上,從混凝土重要力學(xué)因素徐變與松弛的計算理論方法、溫度應(yīng)力計算過程中的重要溫控措施水管冷卻的溫度場有限元計算方法以及結(jié)合具體工程的襯砌混凝土水管冷卻的具體溫控措施等方面進(jìn)行較為深入的研究,主要研究工作如下： 1.分析基于變系數(shù)廣義開爾文模型的混凝土徐變力學(xué)基本方程,研究選取嚴(yán)格對應(yīng)該模型和滿足其物理意義的徐變度Dirichlet級數(shù)表達(dá)式,依據(jù)延遲范圍理論,研究徐變計算模型各參數(shù)的優(yōu)化選取,推導(dǎo)松弛系數(shù)率的表達(dá)式,提出用松弛系數(shù)率求解松弛系數(shù),基于試驗數(shù)據(jù)比較常用徐變度Dirichlet級數(shù)表達(dá)式與松弛系數(shù)的迭加算法。然后,分析基于延遲范圍理論的徐變度模型對襯砌混凝土徐變及早期徐變溫度應(yīng)力計算的影響。 2.在變系數(shù)廣義開爾文模型的基礎(chǔ)上,提出綜合考慮各元件系數(shù)受初始加載時間、觀測時長、作用齡期和作用時長等影響的徐變模型,分析該模型的特點,并研究基于無再次加卸載條件下徐變模型各元件的特點及其在擬合精度上的優(yōu)勢。 3.分析并構(gòu)建水管附近混凝土的熱量平衡方程,采用等效熱傳導(dǎo)原理,推導(dǎo)水管附近任意區(qū)間內(nèi)的平均溫度,并在此基礎(chǔ)上提出利用水管附近混凝土的溫度梯度求解沿程溫升的迭代算法,為提高求解固定網(wǎng)格尺寸下混凝土水管冷卻的真實溫度場的計算精度提供一種新的思路。 4.將混凝土通水冷卻直接模擬法引入水工隧洞襯砌混凝土,研究施工期溪洛渡水工隧洞邊墻襯砌混凝土采用水管冷卻的溫度場與現(xiàn)場對比情況。然后,以在建工程白鶴灘水電站導(dǎo)流洞無壓段襯砌混凝土為例,采用水管冷卻的有限元直接模擬法分析襯砌混凝土通水冷卻的優(yōu)勢和不足,對襯砌混凝土水管冷卻過程中的水管間距、通水水溫和通水流量進(jìn)行敏感性分析并提出有效的冷卻參數(shù)優(yōu)化方案,同時,提出解決不同水管間距下各代表處位置不在同一高度的分析方法,研究結(jié)果可為今后襯砌混凝土水管冷卻的溫控措施提供重要參考。
[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.
【學(xué)位授予單位】：武漢大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：TV554;TV544

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