Efficiency of 3D imaging in GPR diagnostics of joints and vertical construction contacts

The paper discusses the diagnostic abilities of the 3D imaging GPR technique on a practical level, applied to data collected by frequency-domain equipment in reflection configuration and visualized using the method of horizontal slices. This method is particularly efficient in the detection of reinforcement and large infrastructural objects of linear shape. It is especially interesting that the method also allows for the detection of joints and cracks, which are characterized by very weak GPR response. In this case several questions appear as to the nature of response generation and the features of the medium structure which are represented in the scattered signal. The scanned pavement has several layers of different ages and construction styles, and the GPR record illustrates large efficiency of this technique in diagnostics of the joint networks hidden below the asphalt overlay. The example proves reliability of the weak response corresponding to the top of the joints. Some problems related to chronology of responses corresponding to different depth of the medium were discussed. A specific asymmetric response corresponding to two horizontally layered constructions contacting along vertical plane was noted and described as well.