GPR and sonic tomography for structural restoration : the case of the Cathedral of Tricarico

In this paper, we present the results of a diagnostics survey, based on the exploitation of ground penetrating radar (GPR) and sonic prospecting, to characterize the deterioration status of the pillars of the cathedral of Tricarico, in the Basilicata region (Southern Italy). The prospecting falls within the more general framework of investigating the structural conditions of this monument, which is affected by heavy instability problems. This study case points out the great effectiveness of the two employed diagnostic methods, when used in an integrated way, for detecting cracks and inhomogeneities in the inner structure of masonry building elements. With regard to GPR prospecting, a comparison is made between the results obtained by a standard processing and those obtained by means of an inverse scattering algorithm. For one of the investigated pillars, the results obtained from non-invasive tests are compared with those of direct inspection. This is performed by coring the pillar and examining both the core and the hole (the latter by means of an endoscope). The seismic investigation allowed us to prove the mediocre or bad state of conservation of the pillars.