| Cement-based grouting materials have the characteristics of high strength,fast forming,small expansion and large fluidity,and are widely used in building reconstruction and reinforcement projects.When cement-based grouting materials are used in the reconstruction and reinforcement of buildings,a rapid and nondestructive testing method is needed to understand the stress state of key parts.As a rapid and nondestructive testing method,ultrasonic testing technology has been widely used in engineering.In this paper,the cement-based grouting materials are taken as the research object,and the ultrasonic testing technology is applied to carry out the acoustic testing tests at different test points on the reinforced specimens under the load holding state through two acoustic testing methods:horizontal measurement method and pair measurement method.The relevant programs are compiled with MATLAB to carry out signal analysis,statistical analysis and data fitting on the test data,and study the sensitivity between different acoustic parameters and stress,The influencing factors of ultrasonic stress correlation are analyzed,which can provide a reference for the ultrasonic testing technology of grouting materials under stress.In this paper,the sensitivity between acoustic characteristics and stress of cement-based grouting materials is studied.The main research work includes the following aspects:1.through extensive analysis and Research on domestic and foreign literature,the acoustic characteristics-stress sensitive parameters in concrete are discussed,and the ultrasonic signal processing technology is studied and analyzed.Based on the theory of fast Fourier transform and Hilbert Huang transform,the related programs are compiled with MATLAB.2.two kinds of specimens of grouting materials,grouting materials and concrete are designed.The ultrasonic testing tests under the load holding state are carried out by using two ultrasonic testing methods: horizontal measurement method and pair measurement method.The sensitive relationship between the acoustic characteristics and stress of cement-based grouting materials is discussed,which lays a certain test foundation for seeking the sound stress sensitive relationship of cement-based grouting materials.3.the parameters in the horizontal measurement method are optimized.The results show that the wave velocity tends to be stable with the increase of ranging,and more stable results can be obtained when the ranging is greater than 200 mm.4.using MATLAB to compile relevant programs,54 groups of 324 ultrasonic signals in the two types of specimens were processed.It is found that the test results of the grouting material part of the grouting material specimen and the reinforcement specimen are basically the same during the low stress period.The phenomenon and principle that the ultrasonic signal reflects the internal mechanical properties of the cement-based grouting reinforcement specimen are analyzed.5.based on the test data and ultrasonic processing analysis results,the data are fitted and analyzed,and the sensitivity and influencing factors of acoustic parameters and stress fitting curve of cement-based grout reinforced specimens under different stress states are studied.The results show that the acoustic stress correlation is mainly affected by the interface,testing methods and data processing methods;Eight kinds of sound wave parameters sensitive to sound stress and corresponding detection methods are found.In the case of low stress,the horizontal measurement method is used to detect the grouting material surface of the structural reinforcement grouting material,and it has better advantages to obtain the calculated stress of the first wave amplitude parameters under this method.This paper only studies the acoustic parameters under the axial stress elastic state,and puts forward the suggestion of using ultrasonic to nondestructive test cement-based grouting materials.The research team will carry out further research work under complex stress conditions. |
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