Experiences and preliminary results of geophysical methods on historical statues

In recent years, geophysical applications have been significantly grown in rock mechanics field due to their versatility and reliability as diagnostic and/or monitoring tools. Since these methodologies are mainly non-invasive, they can be used for the investigation and characterization of the internal structure of historical artworks or for the monitoring of built cultural heritage, where the non-destructive feature is an indispensable prerequisite. Commonly, the artworks material properties are unknown or strongly altered due to time and physical/chemical agents. Moreover, their nature (mineralogic and petrographic) and origin (in terms of places where the material was exploited) is uncertain and difficult to allocate. Among the available geophysical techniques, seismic methods are useful for detecting the thickness or position of weathered layers, for estimating the physical properties of different materials and for providing information about cracking and degree of fracturing. In this paper, we present some experiences and preliminary results of geophysical characterization of two Tritons statues, discovered in the garden of the Royal Palace of Venaria (Piedmont Region, Italy). The statues were originally part of the Fountain of Hercules, destroyed in the 18th century during the redevelopment works of the Palace. Ultrasonic pulse velocity measurements were performed on each portion of the statues and 3D-imaging of the apparent P-wave velocity were carried out. The performed geophysical investigations were aimed at defining the overall material quality and detecting possible sectors with low resistance properties that might interfere with the coring operations, necessary for the reassembly of the statues. Results of these surveys were also useful for setting up a 3D-FEM model for simulating the material behaviour through an analysis of the forces and loads involved.