| We developed a non-contact surface wave measurement tool using arrayed microphones for the structural investigation of pavements, and tested it on actual pavements. The tool comprises two microphone arrays, each of which is composed of 24 microphones at 5 cm intervals. The microphone arrays are suspended in a sound insulation box cart, 2 cm above the pavement surface. Each microphone is also hooded to reduce direct air wave noises. A PC controlled, 48-channel high-speed data acquisition system is used to observe leaky surface waves. Field measurements demonstrated that the tool could measure leaky surface wave which showed clear dispersion in the frequency range from 150 to 4,000 Hz. S-wave velocity structure of the pavement was successfully reconstructed using the higher modes in dispersion curves. To certify whether the dispersion curves measured by the tool were valid, we conducted comparative surface wave measurements using high-frequency accelerometers pasted on pavement surfaces. In addition, GPR was carried out on the same location to correlate with surface wave measurement results. As a result, 1D S-wave velocity structures reconstructed from the microphone array data were not always concordant with the accelerometer array results. It was presumed that the decrease in S/N of leaky surface waves, caused by surface rough shape and cracks, resulted in inappropriate determination of phase velocities in frequency range from 500 to 900 Hz. Further improvement is planned to enhance the leaky surface wave signals in lower frequency even on damaged pavements. |
