Ground Penetrating Radar Survey

High frequency radar or GPR – Ground Penetrating Radar – survey is carried out for the identification of irregularities or anomalies within a structural element. This geophysical investigation method is based on the propagation and reflection of high frequency electromagnetic waves (range 10 MHz – 3 GHz), emitted by a transmitting antenna and detected by a receiving antenna. The electromagnetic energy is introduced into the system in the form of pulses, propagating, depending on the electromagnetic characteristics of the medium encountered, until it is reflected at the separation interfaces between media having different electrical characteristics, in the presence of differences in electromagnetic impedance (for example in correspondence with metal objects, voids or interfaces between different materials). The reflected signal is then recorded by a receiving antenna. The speed of propagation of electromagnetic waves depends on the dielectric constant of the medium crossed. In the case of land exploration, to obtain greater penetration it is necessary to introduce lower frequency electromagnetic waves into the ground (10-400 MHz). The signal is generally entered and received along longitudinal paths (stripes) or with pre-established mesh acquisitions (grid), with the use of frequencies and sampling times suitable to achieve the best definition and depth in relation to the objectives to be investigated. The completion of the investigation involves the processing of the data using appropriate software, including the transfer, interpretation and graphical display with radargrams.

Reference standards: RILEM TC 127-MS.D.3; ASTM D6432-19.