Research On The Dynamic Characteristics Of The Concrete Under Different Aggregate Gradation

Presently, our country is in a state of rapid development of infrastructure construction, especially for large dams, nuclear power plants, bridges, high-rise buildings, highways which are related to the national economy and critical infrastructure projects are emerging. The mechanical properties of large dam are represented by the data obtained from the tests of small specimens, which is usually made by the full grade aggregate after wet sieving to remove aggregate particles greater than 40 mm. But the great change has taken place in aggregate proportions and structures of the concrete, compared to the raw materials after wet sieving. And the data detected from the small specimen can not reflect the real performance of the concrete dam. So it is especially important to do the research on dynamic performance of the concrete dam.Uniaxial compression test of the concrete with different aggregate gradation are made under different strain rates by multi-static and dynamic triaxial instrument. The acoustic emission(AE) technique is used for real-time monitoring of the failure process of the concrete. By the analysis of experimental data, the law that the peak stress, peak strain and elastic modulus of the concrete under different strain rates and different aggregate gradation is studied. The damage mechanisms of uniaxial compression test of the concrete are analyzed based on the AE data. The dynamic constitutive model is established through mathematical and statistical theory, and the parameters of that are discussed about. The core content and the main innovations of this paper are as follows:1) The uniaxial compression test are carried on to study on the law of the physical and mechanical parameters, such as the peak stress, peak strain and elastic modulus by comparative analysis. The further study of the rate effects on the properties of the concrete under uniaxial compression tests.2) The dynamic constitutive model of the concrete is made on the basis of Weibull statistical theory. And characteristic parameters of characterization of pre-peak stiffness hardening and strain softening after the peak are analyzed. It has been concluded that there exists a little change in stress- strain curve fitting under different strain rates and aggregate gradation. The overall trends of the curves are similar to each other. It is demonstrated that the dynamic constitutive model in the article is effective.3) The synchronous acquisition of AE signals and physical testing is used by acoustic emission software. Through the analysis of AE data, the corresponding relationships among strain, stress and synchronous AE parameters of the concrete are established under different strain rates and loading conditions. The rate of failure mechanism of the concrete is explored under uniaxial compression.