Development of an analytic approach utilizing the extended common midpoint method to estimate asphalt pavement thickness with 3-D ground-penetrating radar

• 3-D GPR can be used to estimate asphalt layer thickness fast.
• Signal-processing techniques are needed to solve XCMP equations accurately.
• The maximum thickness estimation error is 5 mm for layers thicker than 64mm.

As a nondestructive technique, ground-penetrating radar (GPR) has been applied to estimate asphalt pavement thickness. The extended common midpoint (XCMP) method is a method that can be used on the air-coupled, pulsed horn antenna to increase the accuracy of asphalt pavement thickness estimation without calibrating the dielectric constant by taking cores. 3-D GPR is a multi-array, stepped-frequency radar that can measure both in-line and cross-line directions at a very close sampling interval. By developing signal-processing and numerical analysis techniques, this research integrates 3-D GPR with the XCMP method. By validating the developed algorithm at a full-scale test site, the study concludes that by using signal processing techniques and numerical analysis approaches, 3-D GPR can be used to accurately predict asphalt layer thickness using the XCMP method when the layer thickness is greater than 64mm.