To identify shield grouting quality based on impact echo method, an impact echo test of segment-grouting (SG) test piece was\ncarried out to explore effect of acoustic impedance of grouting layers and grouting defects on impact echo law. A finite element\nnumerical simulation on the impact echo process was implemented. Test results and simulation results were compared. Results\ndemonstrated that, under some working conditions, finite element simulation results and test results both agree with theoretical\nvalues. The acoustic impedance ratio of SG material influenced the echo characteristics significantly. But thickness frequency could\nnot be detected under some working conditions because the reflected energy is weak. Frequency feature under grouting defects was\nmore complicated than that under no grouting defects.
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