Electrical resistivity tomography to detect buried cavities in Rome: a case study

Cavities located in shallow layers of the subsoil represent a major hazard especially in sites located in town centres. For this reason, it is necessary to determine their location and size in order to evaluate the risk of subsidence and to draw up plans for restoration and safety. In this study, electrical resistivity tomography was carried out, both to detect cavities and to test a new inversion algorithm that we developed. The cavities are located in a volcanic formation in a public recreation park where there are municipal buildings. The survey was performed using two different arrays: dipole-dipole and Wenner. A new approach to adopting an initial model and inequality constraints was used and the results from different algorithms were compared. The effective range of the dimensions of cavities was determined in order to make an approximate evaluation of ground stability and any potential subsidence hazard.