| Development of non-destructive and high performance testing method has been requested for the pavement assessment. While FWD has been widely utilized as such NDT equipment in Japan, the inversion process of FWD is inherently ambiguous. In contrast, high-frequency surface wave measurements are capable to provide detailed information on the pavement. The authors newly developed a non-contact surface wave measurement tool using arrayed microphones, 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, about 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. Comparative measurements using accelerometers pasted on the pavement surface were conducted to certify whether the tool could discriminate the surface wave phase. As a result, the tool could successfully measure surface waves which showed clear dispersion in the frequency range from 40 to 5,000 Hz. Dispersion curves were essentially same with each other. The field tests demonstrated the tool was quite capable for the continuous pavement assessment. |
