Three-dimensional ground-penetrating radar methodologies for the characterization and volumetric reconstruction of underground tunneling

•Documentation and characterization of underground tunneling space by GPR.•Volumetric reconstruction that allows determining numerical approximation of volumes.•Geometrical dimensioning of the structure from the volumetric reconstruction.•Detection of moist areas from the attenuation of the GPR signal.•FDTD modeling to assist in the interpretation of the field GPR data.

This work presents the documentation and characterization of an ancient underground concrete tunnel using the ground-penetrating radar (GPR) method. Three-dimensional imaging methodologies were applied to create an accurate volumetric reconstruction of the underground tunneling space and the whole framework of galleries composing the main structure, which enabled for the dimensioning of the structure. Problems of moisture were also detected in a particular sector of the tunnel. In addition, FDTD modeling was used to improve the understanding of the GPR signal propagation and to assist the interpretation of the field GPR data. Both field and synthetic data have shown the capabilities of the method for the evaluation and characterization of this ancient construction.