Combined GPR and ERT geophysical assessment of a heritage pier

The evaluation of aging coastal concrete infrastructure such as piers, harbours, and jetties presents challenges in employing large-scale destructive techniques near sensitive areas such as walls. However, these regions are particularly susceptible to deterioration. To address this, a geophysical field survey strategy was deployed utilizing ground-penetrating radar (GPR) and electrical resistivity tomography (ERT) with specialized flat-based electrodes for concrete surfaces. The objective of this survey was to integrate these non-destructive geophysical methods to assess pier structures comprehensively. Through this investigation, areas of preferential deterioration within the structure were identified. Despite GPR’s limited depth of penetration caused by highly conductive infill saturated with seawater, the three-dimensional mapping successfully delineated the first interface and identified potential zones of interest. These findings were corroborated by the joint analysis of the geotechnical report and ERT, which confirmed the presence of the first interface and the high conductivity of the infill material beneath the concrete.