Study on non-destructive testing method of grouting sleeve compactness with wavelet packet energy ratio change

Pre-embedded grouting sleeve in prefabricated shear walls is an effective solution for the longitudinal reinforcement connection issue. However, the compactness of grouting material in sleeve is challenge to be detected. Therefore, grouting quality for sleeve connections is difficult to control. Wavelet packet energy non-destructive testing method is first proposed to test the compactness of grouting sleeves in this paper. Based on the structural characteristics of the grouting sleeve, the defect detection mechanism of ultrasonic elastic wave propagating inside the grouting sleeve was analyzed, and the finite element analysis of coupled solid mechanics - piezoelectric effect was carried out. In the finite element model, the models of the grout-compact sleeve and grout-deficient sleeves with different anchorage length were set up, and the wavelet basis function with the lowest decomposition cost was selected by using the logarithmic energy entropy function. The results of the finite element analysis show that the frequency energy of the grout-deficient sleeve is concentrated in the lower frequency domain compared to the grout-compact sleeve, and that, when accumulated to a certain extent, the phenomenon of main frequency shifted to low-frequency band may occur. In order to verify the applicability in practical grouting sleeves, an ultrasonic non-destructive testing platform was established, and the signal acquisition and denoising process of the grouting sleeves were completed. The measured results show that the method of using the frequency energy to judge the grouting defects is effective. The method studied in this paper can provide reference for engineering application.