冻融循环后大骨料混凝土双轴动态性能试验研究

发布时间：2018-06-23 12:21

本文选题：大骨料混凝土 + 冻融循环　；参考：《大连交通大学》2015年硕士论文

【摘要】：大骨料混凝土主要用于建造水工结构物,如水工大坝、水闸、船坞等。冻害是影响水工结构物耐久性的重要因素。另外,在水工结构物非线性分析中,要充分考虑混凝土所处的应力状态及其所受荷载的加载速率影响,因为在使用过程中,水工结构物中的混凝土多处于双轴和三轴等复杂受力状态,且一般状态下混凝土所受到的荷载的加载速率通常小于10-5/s,而在地震状况下,其所受加载速率一般在10-4/s~10-2/s动态加载范围内。许多学者对大骨料混凝土的力学性能进行了试验研究,主要有单轴应力状态下的静态、动态试验研究,双轴、三轴应力状态下的静态试验研究,但研究多为湿筛混凝土。关于大骨料混凝土的多轴动态试验研究则较少,并且均未考虑冻融循环作用的影响。本文依托清华大学水沙科学与水利水电工程国家重点实验室开放研究基金资助课题——冻融后水工混凝土多轴动态强度及破坏机理研究,对大骨料混凝土进行了冻融循环后动态双轴受压及常态下动态双轴拉压性能试验研究,具体研究内容及结论如下:(1)对大骨料混凝土立方体试件进行了冻融循环试验及动态双轴压缩试验,实测了大骨料混凝土经历不同冻融循环次数后的质量损失、损伤形态,以及不同应力比和应变速率下的破坏形态、极限强度、应力-应变关系曲线。根据试验数据分析了极限强度和变形性能与冻融循环次数、应力比以及应变速率的关系,分别在主应力空间和八面体应力空间建立了冻融循环后大骨料混凝土动态双轴压应力状态下的破坏准则。(2)对常态下大骨料混凝土棱柱体试件进行了动态双轴拉压试验,实测了不同拉压比和应变速率下大骨料混凝土的破坏形态、极限强度和应力-应变关系曲线。根据试验数据分析了极限强度和变形性能与拉压比和应变速率的关系,分别在主应力空间和八面体应力空间建立了大骨料混凝土动态双轴拉压应力状态下的破坏准则。(3)将不同学者对普通混凝土、湿筛混凝土、引气混凝土的双轴极限强度和破坏准则研究成果与本文的试验结果进行对比分析。分析结果表明,大骨料混凝土单轴和双轴抗压强度基本为湿筛混凝土抗压强度的0.7~0.8倍。大骨料混凝土双轴较单轴抗压强度提高幅度小于湿筛混凝土。各类混凝土单轴抗压强度随应变速率提高的幅度均大于双轴抗压强度。冻融循环作用后,普通混凝土与大骨料混凝土双轴抗压强度损失率小于单轴抗压强度损失率。静、动态双轴拉压破坏准则可用直线或二次曲线形式表达。
[Abstract]:Large aggregate concrete is mainly used to build hydraulic structures, such as hydraulic dams, locks, docks, etc. Freezing injury is an important factor affecting the durability of hydraulic structures. In addition, in nonlinear analysis of hydraulic structures, due consideration should be given to the stress state of concrete and the effect of loading rate on the load, because in the process of use, The concrete in hydraulic structures is usually in biaxial and triaxial states, and the loading rate of concrete is usually less than 10 ~ (-5) / s in general state, but in earthquake, the loading rate of concrete is usually less than 10 ~ (-5) / s. The loading rate is generally within the range of dynamic loading of 10-4/s~10-2/s. Many scholars have done experimental research on the mechanical properties of large aggregate concrete, including static, dynamic, biaxial and triaxial stress state, but mostly wet sieve concrete. There are few multiaxial dynamic tests on large aggregate concrete, and the effect of freeze-thaw cycle is not taken into account. Based on the open research fund of the State key Laboratory of Water and sediment Science and Water Conservancy and Hydropower Engineering of Tsinghua University, the research on the multiaxial dynamic strength and failure mechanism of freeze-thawed hydraulic concrete is carried out in this paper. The dynamic biaxial compression behavior of large aggregate concrete under freezing and thawing cycles and the dynamic biaxial tension and compression properties under normal condition were studied. The specific research contents and conclusions are as follows: (1) Freeze-thaw cycle test and dynamic biaxial compression test are carried out on cube specimens of large aggregate concrete. The mass loss and damage form of large aggregate concrete after different freeze-thaw cycles are measured. The failure patterns, ultimate strength and stress-strain curves of different stress ratios and strain rates are also discussed. Based on the experimental data, the relationship between ultimate strength and deformation performance and the number of freeze-thaw cycles, stress ratio and strain rate is analyzed. In the principal stress space and octahedron stress space, the failure criteria of large aggregate concrete under dynamic biaxial compression stress were established respectively. (2) the dynamic biaxial tensile compression tests were carried out on the prism specimens of large aggregate concrete under normal condition. The failure patterns, ultimate strength and stress-strain relationship curves of large aggregate concrete under different tension and compression ratios and strain rates were measured. Based on the experimental data, the relationship between ultimate strength and deformation performance, tensile compression ratio and strain rate is analyzed. In the principal stress space and octahedron stress space respectively, the failure criteria of large aggregate concrete under dynamic biaxial tension and compression stress are established. (3) different scholars are applied to ordinary concrete and wet screen concrete. The research results of biaxial ultimate strength and failure criterion of air-entrained concrete are compared with the experimental results in this paper. The results show that the uniaxial and biaxial compressive strength of large aggregate concrete is 0.7 ~ 0.8 times of that of wet screen concrete. The biaxial compressive strength of large aggregate concrete is smaller than that of wet screen concrete. The increase of uniaxial compressive strength with strain rate is greater than that of biaxial compressive strength. After freeze-thaw cycle, the loss rate of biaxial compressive strength of ordinary concrete and large aggregate concrete is lower than that of uniaxial compressive strength. Static and dynamic biaxial tension-compression failure criteria can be expressed in the form of straight lines or conic curves.
【学位授予单位】：大连交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TU528

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