Research on Ultrasonic Tomography of Concrete Hole Defects Based on Multi-Parameter Coupling and Inversion Initial Value Correction

The combination of ultrasonic method and tomographic imaging technology is a common method to realize the visual defection of concrete hole defects. Herein, a comprehensive identification method was proposed to address the problem of defect misjudgment and missing judgment caused by using a single acoustic parameter as the criterion for ultrasonic testing. Additionally, an image reconstruction method based on inversion initial value correction was used to address the problem of low accuracy in tomographic imaging, which is often characterized by empirical assignment of initial wave velocity and uniform distribution of travel time error. The effectiveness of the modified method was verified through experiments on concrete specimens with different hole sizes and numbers. The results showed that the comprehensive defect discrimination based on the coupling of sound velocity, amplitude and frequency could accurately identify hole defects in concrete, with better accuracy than single-parameter or two-parameter coupling method. The ultrasonic tomography method based on inversion initial value correction could accurately assign the initial value of wave velocity iteration and make the distribution of travel time error more consistent with the defect distribution law.The method was effective for identifying holes larger than 5 mm.