Application of 3D Forward Modelling to Improve the Interpretation of Electrical Resistivity Tomography Results in Architectural Heritage Monuments

The application of Electrical Resistivity Tomography (ERT) for the investigation of architectural heritage has numerous limitations. In most cases, we are referring to historic stone buildings and monuments built from limestone, sandstone, or granite blocks, where many features may complicate the interpretation of electrical resistivity data. First of all, there is incomplete or missing information about principles of building construction and the materials used. Another challenge is the heterogeneity of the masonry as a material due to the presence of many joints between the stone blocks, which may be filled with cementitious materials or be completely or partially empty. For medium-scale studies with limited penetration depth, the presence of air in the joints between stone blocks may affect the electrical resistivity distribution and interfere with the detection of the archaeologically relevant anomalies associated, in particular, with the presence of air cavities. Systematic studies of the applicability of the Electrical Resistivity Tomography in such blocky structures are lacking. In this study, the effect caused by masonry geometry was assessed using numerical 3D modelling of the electrical resistivity distribution in a simplified blocky structure consisting of rows of masonry blocks by incorporating joints between them. The purpose is to study how the presence of air-filled joints affects the ability of the ERT method to detect voids in masonry structures depending on the position and size of these voids. The analysis of numerical models provides insights to facilitate the interpretation of ERT results in historical monuments and other structures constructed from stone blocks.