Three-dimension diagnostic methods of quay wall using focusing acoustic parametric probe and imaging sonar

Collapse and subsidence of quay wall at a harbor are often reported and a diagnosis method to prevent the accident has become a significant concern. To achieve the more accurate assessment of quay wall, we try to develop the new diagnosis method which enables to estimate the inside and outside state of the quay wall from the underwater site. In this study, the outside mapping of the quay wall was conducted using multi-beam echo sounder, and the focusing acoustic parametric probe was developed for the detection of the air hole inside the quay wall. Outside mapping was performed at the port in Chiba. Three-dimensional image of the quay wall was reconstructed from the bathymetry data and seafloor topographys, and the mean tilt angle of quay wall was quantified. The sediments and tilted quay wall were clearly seen in this experiment. The acoustic characteristic of the probe, which was developed for the inner air hole detection, were evaluated in the experimental aquarium using three transmission signals [Summing1, 2 and linear frequency modulation signals (LFM)]. We have succeeded in the observation of the penetration wave passed through the concrete plate of 7 cm thickness. In our study, LFM signal showed the best results of the acoustic characteristics in three ones.