Use of Ground Penetrating Radar to Locate Voids and Estimate Lateral Extent of Grouting Within a Pavement System

A ground penetrating radar (GPR) survey was performed over a pavement system in August 2008 to delineate voids beneath the pavement. Testing was performed over an area of 38.1 m x 45.7 m using a 500-MHz GPR system. Zones of anomalously high reflection amplitude were correlated to a void that had been previously identified by coring, and a second amplitude anomaly was identified in another area of the grid. As a result of the survey, a grouting program was initiated where 22 cubic meters of grout were injected below the pavement into the known void, and into the area corresponding to the second amplitude anomaly. Grouting was completed in November 2008, and the GPR survey was repeated in April 2009. Results from the post-grouting survey revealed that the areas corresponding to the known void and the second amplitude anomaly still possessed amplitude anomalies, but the polarities of the anomalies were reversed relative to the polarities of the anomalies prior to grouting. This indicates that while the air in the voids had a lower dielectric than the overlying pavement, the grout had a higher dielectric. A new anomaly appeared after grouting that was attributed to moisture seeping beneath the concrete at that was not present during the pre-grout survey. The results demonstrate that GPR can be used to identify, delineate, and differentiate between air-filled and grout-filled voids beneath pavement. However, it is important to assess both the amplitude and polarity of the reflections so that anomalies are not misinterpreted.

Language

  • English

Media Info

  • Media Type: DVD
  • Features: Figures; References; Tables;
  • Pagination: 17p
  • Monograph Title: TRB 89th Annual Meeting Compendium of Papers DVD

Subject/Index Terms

Filing Info

  • Accession Number: 01152440
  • Record Type: Publication
  • Report/Paper Numbers: 10-1813
  • Files: TRIS, TRB
  • Created Date: Jan 25 2010 10:50AM