GPR evaluation of the Roman masonry arch bridge of Lugo (Spain)

Many masonry arch bridges are historical constructions still in use within the transportation infrastructure. As their modern functionalities are different from those for which they were originally designed, and because of their age, some have suffered structural transformations over time. Consequently, there has been a recent and continuous increase in the use of non-destructive testing to evaluate historical masonry arch bridges using methods that will not change the historical characteristics of these structures. In Spain, a significant number of masonry arch bridges were constructed between the Roman period and the early 19th century. The Roman bridge of Lugo (NW Spain) was surveyed with GPR to analyze its inner structure from three points of view: historical, archaeological and structural. GPR measurements were performed using 250 and 500 MHz shielded antennas. Interpretation of the data included simulation of FDTD models based on the external geometric measures of the structure. Results revealed the ancient profile of the bridge, as well as many subsoil zones with different fills. GPR provided the unknown inner construction details, which may represent noteworthy information for archaeologists and civil engineers.