| The authors have started a research and development on nondestructive measurements of the pavement using GPR and high-frequency surface wave method. Our goal is to estimate S-wave velocity of the each pavement layer such as asphalt concrete or road base, and to evaluate deterioration and the damage of the pavement. To that end, we think that it is necessary to estimate thickness of pavement accurately by GPR. We conducted some field experiments including GPR measurement at a road which was carried out on a pavement where cracks and wheel ruts were obvious. First, we detected the wheel ruts on a road surface by using vehicle mounted 3D Laser Scanner, and we extracted cracks by visual observation of the road surface. Next we carried out GPR survey of 0.25m grid by using antenna which has a central frequency of 800MHz. From the analysis result of GPR, two subsidence areas of road base along longitudinal direction were caught. The magnitude of the subsidence did not match the depth of wheel ruts. We analyzed the relations between the thickness of road base and the crack distribution. We found that the crack went on increasing at the thinner layer of road base. In order to validate the results of GPR, we conducted borehole camera inspection at several tens of check drillings on the pavement. We confirmed that the estimated thickness of road base was consistent with borehole camera image. In the next phase of application to the high-frequency surface wave method, if we use a priori information of those layer thicknesses as strong constraints, we think that it will be possible to determine more accurate S-wave velocity of the pavement by inverting high frequency dispersion curves. |
