The application of geoelectrical tomographic techniques for the non-destructive testing on masonry structures

The Geophysical Section of the Dipartimento di Ingegneria Civile of the University of Pisa has been active in researches on the application of non-pervasive geophysical surveys on the masonry structures of historical buildings for more then ten years. We used mainly micro-seismic methodologies, both with refraction profiling and tomographic techniques. Recently we started using the shear waves besides the pressure waves that we used until now. The aim was to increase the resolution, as the S-waves have smaller wave-lengths, and to allow an estimation of the Poisson modulus by a dynamic method. Several specific new tools have been designed and set-up for the generation and acquisition of the Swaves, that require a more delicate technology with respect to the P-waves. A series of experiments under different conditions gave very interesting results. Also the technique of geoelectrical tomography has been used for several problems: it proved to be effective in showing areas with anomalous humidity and in individuating voids. The use of micro-geophysical techniques offers many advantages with respects to some “classical” techniques under different angles: velocity of execution, non-pervasiveness and costs.