Volume 31, Issue 3 (May 2008)
Detecting Subsurface Voids Using Ground-Coupled Penetrating Radar
Detecting the presence and extent of subsurface voids under a roadway structure is critical in preventing major failures from occurring. In this study, a 400 MHz Ground-coupled Penetrating Radar (GCPR) was utilized in four projects to locate voids. The air voids present a strong dielectric contrast to GPR waves and therefore these anomalies are clearly identified on GCPR results/plots. In one study, a large void more than 1.8 m in depth was located under the continuous reinforced concrete pavement on IH40 in the Amarillo District of Texas. In total, 3.8 cubic metres of flowable fill was used to fill the void. Voids with depths from 50 to 400 mm were identified and verified in studies on SH6, IH35, and Spur 380. The voids are typically located directly under the surface pavement layer. This study has successfully demonstrated that the GCPR is able to identify void locations. However, drilling and coring should also be done to determine the extent and depth of the void.