GPR is a nondestructive field test that can provide a continuous profile of existing road conditions. GPR can utilize high-speed data collection at speeds up to 50 mph, thus requiring less traffic control and resulting in greater safety. GPR has the potential to be used for a variety of pavement applications, including:
measuring the thickness of asphalt pavement, base and sub-grade; assisting in the analysis of rutting mechanisms; calculating and verifying material properties; locating subsurface objects; detecting stripping and/or layer separation; detecting subsurface moisture; and determining depth to near-surface bedrock and peat deposits.
GPR operates by transmitting short pulses of electromagnetic energy into the ground. The reflected images of these pulses are analyzed using one-dimensional electromagnetic wave propagation theory. These pulses are reflected back to the antenna with amplitudes and arrival times that are related to the dielectric constants of the material layers. Across the interfaces, part of the energy is reflected and part is absorbed, depending on the dielectric contrast of the materials.