混凝土冻融蠕变特性及损伤破裂机理研究

发布时间：2018-03-30 17:01

  本文选题：混凝土　切入点：冻融蠕变　出处：《中国矿业大学》2016年博士论文

【摘要】：随着我国发展西部,振兴东北老工业区,“一带一路”等战略的实施,许多大型混凝土结构工程建设迅速展开,这类工程对人民生活和经济发展起到重要作用,但严酷的环境条件使其寿命大大缩减,其中冻融环境对混凝土结构产生的危害给国家带来重大经济损失。冻融环境下混凝土的蠕变特性及损伤破裂机理研究是解决这类工程结构耐久性问题的基础。本文以粉煤灰混凝土为研究对象,借助于KDS-60快速冻融实验机、微机控制电液伺服蠕变试验系统等现代测试技术,综合应用理论分析,试验研究等方法与手段,对冻融作用后粉煤灰混凝土的一般力学特性、蠕变特性、宏观破裂特征、微细观孔结构及断口特征、理论流变力学模型、冻融蠕变损伤破裂机理等进行了系统研究。主要取得如下研究成果:(1)借助于快速冻融试验机和微机控制电液伺服蠕变试验系统,对未掺加粉煤灰的高强混凝土进行冻融蠕变试验研究,得到了蠕变时程曲线,峰值应力、峰值应变、弹性模量、蠕变变形模量、瞬时应变、蠕变速率、宏观破裂特征等随冻融次数的变化规律。(2)系统测定了粉煤灰混凝土的蠕变特性和冻融蠕变特性,得到了蠕变模量、蠕变速率等随粉煤灰掺量的变化规律,得到了粉煤灰混凝土的蠕变特征曲线、峰值应力、峰值应变、蠕变变形模量、蠕变速率、表观冻融形貌和宏观破坏特征随冻融次数的变化规律。(3)借助扫描电镜测试手段,发现了单孔、不连通孔洞簇、连通孔洞簇和粉煤灰孔洞四种孔洞形貌特征,河流花、台阶花、层叠花、半球面花、不规则花五种脆性断裂特征和韧窝、峰林两种韧性断裂特征,得到了混凝土微细观孔结构和断口形貌特征随粉煤灰掺量和冻融次数的变化规律。(4)基于材料流变力学和损伤力学理论,建立了非线性粘弹塑性流变力学模型(MSSB-NVPB和孙钧-NVPB模型),分别用于描述未冻融和冻融时粉煤灰混凝土的流变特性,推导了对应的本构方程、蠕变方程、卸载方程和松弛方程,结合粉煤灰混凝土冻融蠕变加卸载试验数据,求解了模型参数,分析了其与粉煤灰掺量和冻融次数的变化规律,模型理论值与试验值吻合较好。(5)建立了粉煤灰掺量m和冻融次数n的混凝土损伤演化方程;提出了考虑损伤的非线性粘弹塑性蠕变损伤模型,推导出了其相对应的损伤蠕变方程。
[Abstract]:As China's western development, the revitalization of northeast old industrial zone, "the implementation of The Belt and Road" strategy, many large concrete structure engineering construction started quickly, this kind of project to play an important role in people's life and economic development, but the harsh environmental conditions so life is greatly reduced, the freezing thawing hazards on environment the concrete structure has brought great economic loss to the country. The freeze-thaw damage of concrete creep and rupture mechanism of environment is the basis to solve the durability problem of this kind of engineering. In this paper, the fly ash concrete as the research object, with the help of KDS-60 rapid freeze-thaw test machine, computer controlled electro-hydraulic servo system and other modern test creep test technical analysis, comprehensive application of theory, methods and means of experimental research, the general mechanical properties of freezing, thawing after fly ash concrete creep characteristics, macro fracture characteristics, micro The concept of pore structure and fracture characteristics, the theory of rheological model, freeze-thaw damage creep fracture mechanism were studied. The main research results are as follows: (1) by rapid freezing and thawing of the electro-hydraulic servo control system test and creep test of high-strength concrete on the computer, not adding fly ash to freeze-thaw of creep test, the creep curve, peak stress, peak strain, elastic modulus, creep deformation modulus, instantaneous strain, creep rate, rupture characteristics of macro variations with the number of freeze-thaw cycles. (2) system for the determination of creep properties of fly ash concrete and freeze-thaw creep, creep modulus is obtained and the variation of the creep rate such as the amount of fly ash, the creep characteristic curve of fly ash concrete, peak stress, peak strain, creep deformation modulus, creep rate, apparent morphology and freeze-thaw macrocharacters with freezing Changes of the number of freeze-thaw. (3) by scanning electron microscopy test means, found a single hole, not connected hole cluster, connected hole cluster and fly ash hole four hole river morphology, flower, flower flower stage, stacked, hemispherical flowers, irregular flowers five brittle fracture and dimple, two characteristic peaks of ductile fracture, the concrete micro pore structure and fracture morphology with fly ash and variation of freeze-thaw cycles. (4) the rheological mechanics and material based on the theory of damage mechanics, the nonlinear viscoelastic plastic rheological model (MSSB-NVPB and Sun Jun -NVPB model), which are used to describe not the rheological properties of fly ash concrete freezing and thawing, constitutive equation, the corresponding deduced creep equation, unloading equation and the relaxation equation, combined with fly ash concrete freeze-thaw creep loading and unloading test data, solving the parameters of the model, and its analysis Fly ash and freeze thawing times changes, the model theoretical value is in good agreement with the experimental results. (5) the establishment of the fly ash concrete damage evolution equation m and freeze thawing times of N; the damage of nonlinear viscoelastic plastic creep damage model considering creep damage equation was deduced by the the corresponding.

【学位授予单位】：中国矿业大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TU528
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本文编号：1686809