GPR Tomography Feasibility Study in the Process of Air-filled Voids Search in Engineering Structures

Non-destructive testing of buildings and structures appears acutely on the agenda. The load-bearing capacity of structures apart from the concrete strength depends on the defects of the internal structure. These defects can be caused by voids of various size and origin. The GPR is known as one of the nondestructive methods of internal structure study. In some cases the conventional GPR sounding doesn’t allow solving the problem of voids’ detection. The GPR tomography can afford a better solution, eliminating the disadvantages of the sounding and offering a quantitative result: the electromagnetic waves’ velocity and amplitude values. The present paper focuses on the analysis of GPR tomography potential aimed at the search of voids of various dimensions by the example of isometric concrete structure (a construction or a bridge pillar). Mathematic modeling and in situ measurements on a pillar with a known structure, containing a void inside were carried out in order to attain the claimed objective. The paper demonstrates that the voids within the range of two wavelengths (20sm) can be successfully delineated, regardless of their position, on the basis of the following indicators: ray bending at the boundary of the void and velocity increase by more than 30%.