The Use of Ultra-Wide Band GPR for the Detection of Voiding and Other Artefacts in Bridge Abutments and Related Retaining Structures

The structural integrity of bridge abutments and retaining structures can be compromised by the presence of voids. Structural deformations visible on the surface of structures that are indicative of voiding may not indicate the actual location of voids within the structure, therefore, pinpointing problem areas can be problematic. Traditional destructive methods of investigating these structures (including drilling and borescope inspection) generally only provide limited information at a single point; they also have the potential to cause damage to the structure during investigation.. Standard GPR (Ground Penetrating Radar) methods are utilised as a supplement and/or alternative to traditional methods of investigation but have limitation of depth and resolution. Ultra-wide band GPR methods provide an efficient non-destructive method for the detection of voiding while maintaining resolution over a broader depth range than that of other GPR methods.

Most GPR devices use an antenna that has a discrete peak frequency which provides a resolution at a specific depth. To investigate different depths, several different GPR antennae must be utilised with varying peak frequencies. As these antennae only have a peak frequency, resolution falls at depths which are outside of the specific depth related to the peak frequency of the respective antennae. Ultra-wide band GPR differs from standard GPR devices by having a range of peak frequencies that enable it to maintain the resolution over a broader depth range.

This paper provides a discussion on the feasibility of ultra-wide band GPR as a tool to investigate voiding of bridge abutments and retaining structures. It also provides a description of the methodology utilised for the assessment of ultra-wide band GPR technology and a description of its potential suitability for other uses.