Ground-penetrating radar investigations for urban roads

Although ground-penetrating radar (GPR) technology has existed for many decades, it has only been in the last 15 to 20 years that it has undergone great development and is now a commonly used non-destructive technique to assess layer thicknesses and material condition of trunk road pavement structures. Intrusive investigations provide vital additional information, but are often costly and time-consuming, and have the limitation that only data at discrete points are obtained. The nature of urban sites means that ground conditions are highly variable, and urban pavements are often subject to much maintenance and reconstruction. This can result in roads containing several pavement types or layers of materials of differing age and condition, often overlying discrete buried objects, services or structures. Other site-specific factors can also affect the quality of data obtained. However, it is possible to tailor a GPR survey to optimise data by adjusting the investigation methodology. Using an example of a recent urban pavement investigation, this paper shows how the use of detailed and extensive GPR data collection can be used to target concurrent invasive investigations to optimise the analysis of variable urban pavement structures and hence focus maintenance treatments and methodologies.