Time-Frequency Analysis of Impact Echo Signals of Grouting Defects in Tunnels

Abstract—Defects in the grouting layer are hidden problems of underground engineering quality, while it plays an important role in the stability of the overall structure of the tunnel segment, the earth pressure transmission and impermeability. There is no accurate means for the detection of the grouting layer so far. As a non-destructive testing method with single detection surface, the impact-echo method is widely used in the detection of cracks, delamination, voids, etc. in concrete structures. In this paper, the impact-echo method was used to detect the grouting defect in grouting-segment structure. Combined with the finite element and the test structure, the signal was analyzed in the time-frequency domain. The results show that the finite element results are in good agreement with the experimental results and the accuracy of frequency distribution characteristics results meets the engineering needs. The time-frequency analysis can provide a foundation for the qualitative judgment of defects.